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diff --git a/imap/docs/rfc/README b/imap/docs/rfc/README
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+The following documents are necessary to understand the syntax rules
+most of the remaining documents.  Note that some documents refer to
+RFC 2234 which has been replaced by RFC 5234:
+   rfc5234.txt	Augmented BNF for Syntax Specifications - ABNF
+   rfc4466.txt	Collected Extensions to IMAP4 ABNF
+
+
+The following documents specify the IMAP protocol:
+   rfc3501.txt	Internet Message Access Protocol - Version 4rev1
+
+
+The following documents provide additional information which is useful
+in understanding the IMAP protocol:
+   rfc1733.txt	Distributed Electronic Mail Models in IMAP4
+   rfc2180.txt	IMAP4 Multi-Accessed Mailbox Practice
+   rfc2683.txt	IMAP4 Implementation Recommendations
+   rfc4549.txt	Synchronization Operations for Disconnected IMAP4 Clients
+
+
+The following documents describe extensions to the IMAP protocol.
+Items marked with "*" are supported in this distribution:
+   rfc4314.txt	ACL
+ * rfc3516.txt	BINARY
+   rfc4469.txt	CATENATE
+ * rfc3348.txt	CHILDREN
+   rfc4978.txt	COMPRESS
+   rfc4551.txt	CONDSTORE
+   rfc5161.txt	ENABLE
+ * rfc4731.txt	ESEARCH
+   rfc2971.txt	ID
+ * rfc2177.txt	IDLE
+ * rfc2088.txt	LITERAL+
+ * rfc2221.txt	LOGIN-REFERRALS
+ * rfc2193.txt	MAILBOX-REFERRALS
+ * rfc3502.txt	MULTIAPPEND
+ * rfc2342.txt	NAMESPACE
+   rfc5162.txt	QRESYNC
+   rfc2087.txt	QUOTA
+ * rfc4959.txt	SASL-IR
+ * rfc4315.txt	UIDPLUS
+ * rfc3691.txt	UNSELECT
+   rfc4467.txt	URLAUTH
+ * rfc5032.txt	WITHIN
+
+
+The following documents describe SASL:
+   rfc4422.txt	Simple Authentication and Security Layer (SASL)
+and the SASL mechanisms supported in this distribution:
+   rfc4505.txt	ANONYMOUS
+   rfc2195.txt	CRAM-MD5
+   rfc4752.txt	GSSAPI
+   rfc4616.txt	PLAIN
+
+
+The following documents relate to internationalization issues:
+   rfc4790.txt	Internet Application Protocol Collation Registry
+   rfc5051.txt	i;unicode-casemap - Simple Unicode Collation Algorithm
+
+
+The following documents are primarily of historic interest:
+   rfc1732.txt	IMAP4 Compatibility with IMAP2 and IMAP2bis
+   rfc2061.txt	IMAP4 Compatibility with IMAP2bis
+   rfc2062.txt	Internet Message Access Protocol - Obsolete Syntax
+
+
+The following documents discuss matters which are related to IMAP:
+   rfc3503.txt	MDN Profile for IMAP
+   rfc3656.txt	MUPDATE Distributed Mailbox Database Protocol
+   rfc4468.txt	Message Submission BURL Extension
+   rfc5092.txt	IMAP URL Scheme
diff --git a/imap/docs/rfc/rfc1732.txt b/imap/docs/rfc/rfc1732.txt
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+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 1732                      University of Washington
+Category: Informational                                    December 1994
+
+
+              IMAP4 COMPATIBILITY WITH IMAP2 AND IMAP2BIS
+
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  This memo
+   does not specify an Internet standard of any kind.  Distribution of
+   this memo is unlimited.
+
+Introduction
+
+   This is a summary of hints and recommendations to enable an IMAP4
+   implementation to interoperate with implementations that conform to
+   earlier specifications.  None of these hints and recommendations are
+   required by the IMAP4 specification; implementors must decide for
+   themselves whether they want their implementation to fail if it
+   encounters old software.
+
+   IMAP4 has been designed to be upwards compatible with earlier
+   specifications.  For the most part, IMAP4 facilities that were not in
+   earlier specifications should be invisible to clients unless the
+   client asks for the facility.
+
+   In some cases, older servers may support some of the capabilities
+   listed as being "new in IMAP4" as experimental extensions to the
+   IMAP2 protocol described in RFC 1176.
+
+   This information may not be complete; it reflects current knowledge
+   of server and client implementations as well as "folklore" acquired
+   in the evolution of the protocol.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                                                         [Page 1]
+
+RFC 1732                 IMAP4 - Compatibility             December 1994
+
+
+IMAP4 client interoperability with old servers
+
+   In general, a client should be able to discover whether an IMAP2
+   server supports a facility by trial-and-error; if an attempt to use a
+   facility generates a BAD response, the client can assume that the
+   server does not support the facility.
+
+   A quick way to check whether a server implementation supports the
+   IMAP4 specification is to try the CAPABILITY command.  An OK response
+   that includes the IMAP4 capability value indicates a server that
+   supports IMAP4; a BAD response or one without the IMAP4 capability
+   value indicates an older server.
+
+   The following is a list of facilities that are only in IMAP4, and
+   suggestions for how new clients might interoperate with old servers:
+
+   CAPABILITY command
+            A BAD response to this command indicates that the server
+            implements IMAP2 (or IMAP2bis) and not IMAP4.
+
+   AUTHENTICATE command.
+            Use the LOGIN command.
+
+   LSUB and LIST commands
+            Try the RFC 1176 FIND command.
+
+   * in a sequence
+            Use the number of messages in the mailbox from the EXISTS
+            unsolicited response.
+
+   SEARCH extensions (character set, additional criteria)
+            Reformulate the search request using only the searching
+            options listed in search_old in the IMAP4 grammar.  This may
+            entail doing multiple searches to achieve the desired
+            results.
+
+   BODYSTRUCTURE fetch data item
+            Try to fetch the non-extensible BODY data item.
+
+   body section number 0
+            Fetch the entire message and extract the header.
+
+   RFC822.HEADER.LINES and RFC822.HEADER.LINES.NOT fetch data items
+            Use RFC822.HEADER and remove the unwanted information.
+
+   BODY.PEEK[section], RFC822.PEEK, and RFC822.TEXT.PEEK fetch data
+            items Use the corresponding non-PEEK versions and manually
+            clear the \Seen flag as necessary.
+
+
+
+Crispin                                                         [Page 2]
+
+RFC 1732                 IMAP4 - Compatibility             December 1994
+
+
+   UID fetch data item and the UID commands
+            No equivalent capabilitity exists in older servers.
+
+   FLAGS.SILENT, +FLAGS.SILENT, and -FLAGS.SILENT store data items
+            Use the corresponding non-SILENT versions and ignore the
+            untagged FETCH responses which com eback.
+
+
+   The following IMAP4 facilities were introduced in the experimental
+   IMAP2bis revisions to RFC-1176, and may be present in a server that
+   does not support the CAPABILITY command:
+
+   CREATE, DELETE, and RENAME commands
+            To test whether these commands are present, try a CREATE
+            INBOX command.  If the response is NO, these commands are
+            supported by the server.  If the response is BAD, they are
+            not.  Older servers without the CREATE capability may sup-
+            port implicit creation of a mailbox by a COPY command with a
+            non-existant name as the destination.
+
+   APPEND command
+            To test whether this command is present, try to append a
+            zero-length stream to a mailbox name that is known not to
+            exist (or at least, highly unlikely to exist) on the remote
+            system.
+
+   SUBSCRIBE and UNSUBSCRIBE commands
+            Try the form of these commands with the optional MAILBOX
+            keyword.
+
+   EXAMINE command
+            Use the SELECT command instead.
+
+   flags and internal date argument to APPEND command
+            Try the APPEND without any flag list and internal date argu-
+            ments.
+
+   BODY, BODY[section], and FULL fetch data items
+            Use RFC822.TEXT and ALL instead.  Server does not support
+            MIME.
+
+   PARTIAL command
+            Use the appropriate FETCH command and ignore the unwanted
+            data.
+
+
+   IMAP4 client implementations must accept all responses and data for-
+   mats documented in the IMAP4 specification, including those labeled
+
+
+
+Crispin                                                         [Page 3]
+
+RFC 1732                 IMAP4 - Compatibility             December 1994
+
+
+   as obsolete.  This includes the COPY and STORE unsolicited responses
+   and the old format of dates and times.  In particular, client imple-
+   mentations must not treat a date/time as a fixed format string; nor
+   may they assume that the time begins at a particular octet.
+
+   IMAP4 client implementations must not depend upon the presence of any
+   server extensions that are not in the base IMAP4 specification.
+
+   The experimental IMAP2bis version specified that the TRYCREATE spe-
+   cial information token is sent as a separate unsolicited OK response
+   instead of inside the NO response.
+
+   The FIND BBOARDS, FIND ALL.BBOARDS, and BBOARD commands of RFC 1176
+   are removed from IMAP4.  There is no equivalent to the bboard com-
+   mands, which provided a separate namespace with implicit restrictions
+   on what may be done in that namespace.
+
+   Older server implementations may automatically create the destination
+   mailbox on COPY if that mailbox does not already exist.  This was how
+   a new mailbox was created in older specifications.  If the server
+   does not support the CREATE command (see above for how to test for
+   this), it will probably create a mailbox on COPY.
+
+   Older server implementations may not preserve flags or internal dates
+   on COPY.  Some server implementations may not permit the preservation
+   of certain flags on COPY or their setting with APPEND as site policy.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                                                         [Page 4]
+
+RFC 1732                 IMAP4 - Compatibility             December 1994
+
+
+IMAP4 server interoperability with old clients
+
+   In general, there should be no interoperation problem between a
+   server conforming to the IMAP4 specification and a well-written
+   client that conforms to an earlier specification.  Known problems are
+   noted below:
+
+      Poor wording in the description of the CHECK command in earlier
+      specifications implied that a CHECK command is the way to get the
+      current number of messages in the mailbox.  This is incorrect.  A
+      CHECK command does not necessarily result in an EXISTS response.
+      Clients must remember the most recent EXISTS value sent from the
+      server, and should not generate unnecessary CHECK commands.
+
+      An incompatibility exists with COPY in IMAP4.  COPY in IMAP4
+      servers does not automatically create the destination mailbox if
+      that mailbox does not already exist.  This may cause problems with
+      old clients that expect automatic mailbox creation in COPY.
+
+      The PREAUTH unsolicited response is new in IMAP4.  It is highly
+      unlikely that an old client would ever see this response.
+
+      The format of dates and times has changed due to the impending end
+      of the century.  Clients that fail to accept a four-digit year or
+      a signed four-digit timezone value will not work properly with
+      IMAP4.
+
+      An incompatibility exists with the use of "\" in quoted strings.
+      This is best avoided by using literals instead of quoted strings
+      if "\" or <"> is embedded in the string.
+
+Security Considerations
+
+   Security issues are not discussed in this memo.
+
+Author's Address:
+
+   Mark R. Crispin
+   Networks and Distributed Computing, JE-30
+   University of Washington
+   Seattle, WA  98195
+
+   Phone: (206) 543-5762
+
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+Crispin                                                         [Page 5]
+
diff --git a/imap/docs/rfc/rfc1733.txt b/imap/docs/rfc/rfc1733.txt
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+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 1733                      University of Washington
+Category: Informational                                    December 1994
+
+
+              DISTRIBUTED ELECTRONIC MAIL MODELS IN IMAP4
+
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  This memo
+   does not specify an Internet standard of any kind.  Distribution of
+   this memo is unlimited.
+
+
+Distributed Electronic Mail Models
+
+   There are three fundamental models of client/server email: offline,
+   online, and disconnected use.  IMAP4 can be used in any one of these
+   three models.
+
+   The offline model is the most familiar form of client/server email
+   today, and is used by protocols such as POP-3 (RFC 1225) and UUCP.
+   In this model, a client application periodically connects to a
+   server.  It downloads all the pending messages to the client machine
+   and deletes these from the server.  Thereafter, all mail processing
+   is local to the client.  This model is store-and-forward; it moves
+   mail on demand from an intermediate server (maildrop) to a single
+   destination machine.
+
+   The online model is most commonly used with remote filesystem
+   protocols such as NFS.  In this model, a client application
+   manipulates mailbox data on a server machine.  A connection to the
+   server is maintained throughout the session.  No mailbox data are
+   kept on the client; the client retrieves data from the server as is
+   needed.  IMAP4 introduces a form of the online model that requires
+   considerably less network bandwidth than a remote filesystem
+   protocol, and provides the opportunity for using the server for CPU
+   or I/O intensive functions such as parsing and searching.
+
+   The disconnected use model is a hybrid of the offline and online
+   models, and is used by protocols such as PCMAIL (RFC 1056).  In this
+   model, a client user downloads some set of messages from the server,
+   manipulates them offline, then at some later time uploads the
+   changes.  The server remains the authoritative repository of the
+   messages.  The problems of synchronization (particularly when
+   multiple clients are involved) are handled through the means of
+   unique identifiers for each message.
+
+
+
+Crispin                                                         [Page 1]
+
+RFC 1733                     IMAP4 - Model                 December 1994
+
+
+   Each of these models have their own strengths and weaknesses:
+
+      Feature                               Offline Online  Disc
+      -------                               ------- ------  ----
+      Can use multiple clients               NO      YES     YES
+      Minimum use of server connect time     YES     NO      YES
+      Minimum use of server resources        YES     NO      NO
+      Minimum use of client disk resources   NO      YES     NO
+      Multiple remote mailboxes              NO      YES     YES
+      Fast startup                           NO      YES     NO
+      Mail processing when not online        YES     NO      YES
+
+   Although IMAP4 has its origins as a protocol designed to accommodate
+   the online model, it can support the other two models as well.  This
+   makes possible the creation of clients that can be used in any of the
+   three models.  For example, a user may wish to switch between the
+   online and disconnected models on a regular basis (e.g. owing to
+   travel).
+
+   IMAP4 is designed to transmit message data on demand, and to provide
+   the facilities necessary for a client to decide what data it needs at
+   any particular time.  There is generally no need to do a wholesale
+   transfer of an entire mailbox or even of the complete text of a
+   message.  This makes a difference in situations where the mailbox is
+   large, or when the link to the server is slow.
+
+   More specifically, IMAP4 supports server-based RFC 822 and MIME
+   processing.  With this information, it is possible for a client to
+   determine in advance whether it wishes to retrieve a particular
+   message or part of a message.  For example, a user connected to an
+   IMAP4 server via a dialup link can determine that a message has a
+   2000 byte text segment and a 40 megabyte video segment, and elect to
+   fetch only the text segment.
+
+   In IMAP4, the client/server relationship lasts only for the duration
+   of the TCP connection.  There is no registration of clients.  Except
+   for any unique identifiers used in disconnected use operation, the
+   client initially has no knowledge of mailbox state and learns it from
+   the IMAP4 server when a mailbox is selected.  This initial transfer
+   is minimal; the client requests additional state data as it needs.
+
+   As noted above, the choice for the location of mailbox data depends
+   upon the model chosen.  The location of message state (e.g. whether
+   or not a message has been read or answered) is also determined by the
+   model, and is not necessarily the same as the location of the mailbox
+   data.  For example, in the online model message state can be co-
+   located with mailbox data; it can also be located elsewhere (on the
+   client or on a third agent) using unique identifiers to achieve
+
+
+
+Crispin                                                         [Page 2]
+
+RFC 1733                     IMAP4 - Model                 December 1994
+
+
+   common reference across sessions.  The latter is particularly useful
+   with a server that exports public data such as netnews and does not
+   maintain per-user state.
+
+   The IMAP4 protocol provides the generality to implement these
+   different models.  This is done by means of server and (especially)
+   client configuration, and not by requiring changes to the protocol or
+   the implementation of the protocol.
+
+
+Security Considerations
+
+   Security issues are not discussed in this memo.
+
+
+Author's Address:
+
+   Mark R. Crispin
+   Networks and Distributed Computing, JE-30
+   University of Washington
+   Seattle, WA  98195
+
+   Phone: (206) 543-5762
+
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
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+
+
+
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+
+
+Crispin                                                         [Page 3]
+
diff --git a/imap/docs/rfc/rfc2061.txt b/imap/docs/rfc/rfc2061.txt
new file mode 100644
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+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 2061                      University of Washington
+Category: Informational                                    December 1996
+
+
+                   IMAP4 COMPATIBILITY WITH IMAP2BIS
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  This memo
+   does not specify an Internet standard of any kind.  Distribution of
+   this memo is unlimited.
+
+Introduction
+
+   The Internet Message Access Protocol (IMAP) has been through several
+   revisions and variants in its 10-year history.  Many of these are
+   either extinct or extremely rare; in particular, several undocumented
+   variants and the variants described in RFC 1064, RFC 1176, and RFC
+   1203 fall into this category.
+
+   One variant, IMAP2bis, is at the time of this writing very common and
+   has been widely distributed with the Pine mailer.  Unfortunately,
+   there is no definite document describing IMAP2bis.  This document is
+   intended to be read along with RFC 1176 and the most recent IMAP4
+   specification (RFC 2060) to assist implementors in creating an IMAP4
+   implementation to interoperate with implementations that conform to
+   earlier specifications.  Nothing in this document is required by the
+   IMAP4 specification; implementors must decide for themselves whether
+   they want their implementation to fail if it encounters old software.
+
+   At the time of this writing, IMAP4 has been updated from the version
+   described in RFC 1730.  An implementor who wishes to interoperate
+   with both RFC 1730 and RFC 2060 should refer to both documents.
+
+   This information is not complete; it reflects current knowledge of
+   server and client implementations as well as "folklore" acquired in
+   the evolution of the protocol.  It is NOT a description of how to
+   interoperate with all variants of IMAP, but rather with the old
+   variant that is most likely to be encountered.  For detailed
+   information on interoperating with other old variants, refer to RFC
+   1732.
+
+IMAP4 client interoperability with IMAP2bis servers
+
+   A quick way to check whether a server implementation supports the
+   IMAP4 specification is to try the CAPABILITY command.  An OK response
+   will indicate which variant(s) of IMAP4 are supported by the server.
+
+
+
+Crispin                      Informational                      [Page 1]
+
+RFC 2061                  IMAP4 Compatibility              December 1996
+
+
+   If the client does not find any of its known variant in the response,
+   it should treat the server as IMAP2bis.  A BAD response indicates an
+   IMAP2bis or older server.
+
+   Most IMAP4 facilities are in IMAP2bis.  The following exceptions
+   exist:
+
+   CAPABILITY command
+            The absense of this command indicates IMAP2bis (or older).
+
+   AUTHENTICATE command.
+            Use the LOGIN command.
+
+   LSUB, SUBSCRIBE, and UNSUBSCRIBE commands
+            No direct functional equivalent.  IMAP2bis had a concept
+            called "bboards" which is not in IMAP4.  RFC 1176 supported
+            these with the BBOARD and FIND BBOARDS commands.  IMAP2bis
+            augmented these with the FIND ALL.BBOARDS, SUBSCRIBE BBOARD,
+            and UNSUBSCRIBE BBOARD commands.  It is recommended that
+            none of these commands be implemented in new software,
+            including servers that support old clients.
+
+   LIST command
+            Use the command FIND ALL.MAILBOXES, which has a similar syn-
+            tax and response to the FIND MAILBOXES command described in
+            RFC 1176.  The FIND MAILBOXES command is unlikely to produce
+            useful information.
+
+   * in a sequence
+            Use the number of messages in the mailbox from the EXISTS
+            unsolicited response.
+
+   SEARCH extensions (character set, additional criteria)
+            Reformulate the search request using only the RFC 1176 syn-
+            tax.  This may entail doing multiple searches to achieve the
+            desired results.
+
+   BODYSTRUCTURE fetch data item
+            Use the non-extensible BODY data item.
+
+   body sections HEADER, TEXT, MIME, HEADER.FIELDS, HEADER.FIELDS.NOT
+            Use body section numbers only.
+
+   BODY.PEEK[section]
+            Use BODY[section] and manually clear the \Seen flag as
+            necessary.
+
+
+
+
+
+Crispin                      Informational                      [Page 2]
+
+RFC 2061                  IMAP4 Compatibility              December 1996
+
+
+   FLAGS.SILENT, +FLAGS.SILENT, and -FLAGS.SILENT store data items
+            Use the corresponding non-SILENT versions and ignore the
+            untagged FETCH responses which come back.
+
+   UID fetch data item and the UID commands
+            No functional equivalent.
+
+   CLOSE command
+            No functional equivalent.
+
+
+   In IMAP2bis, the TRYCREATE special information token is sent as a
+   separate unsolicited OK response instead of inside the NO response.
+
+   IMAP2bis is ambiguous about whether or not flags or internal dates
+   are preserved on COPY.  It is impossible to know what behavior is
+   supported by the server.
+
+IMAP4 server interoperability with IMAP2bis clients
+
+   The only interoperability problem between an IMAP4 server and a
+   well-written IMAP2bis client is an incompatibility with the use of
+   "\" in quoted strings.  This is best avoided by using literals
+   instead of quoted strings if "\" or <"> is embedded in the string.
+
+Security Considerations
+
+   Security issues are not discussed in this memo.
+
+Author's Address
+
+   Mark R. Crispin
+   Networks and Distributed Computing
+   University of Washington
+   4545 15th Aveneue NE
+   Seattle, WA  98105-4527
+
+   Phone: (206) 543-5762
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                      Informational                      [Page 3]
+
diff --git a/imap/docs/rfc/rfc2062.txt b/imap/docs/rfc/rfc2062.txt
new file mode 100644
index 00000000..865d1dad
--- /dev/null
+++ b/imap/docs/rfc/rfc2062.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 2062                      University of Washington
+Category: Informational                                    December 1996
+
+
+           Internet Message Access Protocol - Obsolete Syntax
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  This memo
+   does not specify an Internet standard of any kind.  Distribution of
+   this memo is unlimited.
+
+Abstract
+
+   This document describes obsolete syntax which may be encountered by
+   IMAP4 implementations which deal with older versions of the Internet
+   Mail Access Protocol.  IMAP4 implementations MAY implement this
+   syntax in order to maximize interoperability with older
+   implementations.
+
+   This document repeats information from earlier documents, most
+   notably RFC 1176 and RFC 1730.
+
+Obsolete Commands and Fetch Data Items
+
+   The following commands are OBSOLETE.  It is NOT required to support
+   any of these commands or fetch data items in new server
+   implementations.  These commands are documented here for the benefit
+   of implementors who may wish to support them for compatibility with
+   old client implementations.
+
+   The section headings of these commands are intended to correspond
+   with where they would be located in the main document if they were
+   not obsoleted.
+
+6.3.OBS.1.      FIND ALL.MAILBOXES Command
+
+   Arguments:  mailbox name with possible wildcards
+
+   Data:       untagged responses: MAILBOX
+
+   Result:     OK - find completed
+               NO - find failure: can't list that name
+               BAD - command unknown or arguments invalid
+
+
+
+
+
+
+Crispin                      Informational                      [Page 1]
+
+RFC 2062                     IMAP4 Obsolete                December 1996
+
+
+      The FIND ALL.MAILBOXES command returns a subset of names from the
+      complete set of all names available to the user.  It returns zero
+      or more untagged MAILBOX replies.  The mailbox argument to FIND
+      ALL.MAILBOXES is similar to that for LIST with an empty reference,
+      except that the characters "%" and "?" match a single character.
+
+   Example:    C: A002 FIND ALL.MAILBOXES *
+               S: * MAILBOX blurdybloop
+               S: * MAILBOX INBOX
+               S: A002 OK FIND ALL.MAILBOXES completed
+
+6.3.OBS.2.      FIND MAILBOXES Command
+
+   Arguments:  mailbox name with possible wildcards
+
+   Data:       untagged responses: MAILBOX
+
+   Result:     OK - find completed
+               NO - find failure: can't list that name
+               BAD - command unknown or arguments invalid
+
+      The FIND MAILBOXES command returns a subset of names from the set
+      of names that the user has declared as being "active" or
+      "subscribed".  It returns zero or more untagged MAILBOX replies.
+      The mailbox argument to FIND MAILBOXES is similar to that for LSUB
+      with an empty reference, except that the characters "%" and "?"
+      match a single character.
+
+   Example:    C: A002 FIND MAILBOXES *
+               S: * MAILBOX blurdybloop
+               S: * MAILBOX INBOX
+               S: A002 OK FIND MAILBOXES completed
+
+6.3.OBS.3.      SUBSCRIBE MAILBOX Command
+
+   Arguments:  mailbox name
+
+   Data:       no specific data for this command
+
+   Result:     OK - subscribe completed
+               NO - subscribe failure: can't subscribe to that name
+               BAD - command unknown or arguments invalid
+
+      The SUBSCRIBE MAILBOX command is identical in effect to the
+      SUBSCRIBE command.  A server which implements this command must be
+      able to distinguish between a SUBSCRIBE MAILBOX command and a
+      SUBSCRIBE command with a mailbox name argument of "MAILBOX".
+
+
+
+
+Crispin                      Informational                      [Page 2]
+
+RFC 2062                     IMAP4 Obsolete                December 1996
+
+
+   Example:    C: A002 SUBSCRIBE MAILBOX #news.comp.mail.mime
+               S: A002 OK SUBSCRIBE MAILBOX to #news.comp.mail.mime
+               completed
+               C: A003 SUBSCRIBE MAILBOX
+               S: A003 OK SUBSCRIBE to MAILBOX completed
+
+
+6.3.OBS.4.      UNSUBSCRIBE MAILBOX Command
+
+   Arguments:  mailbox name
+
+   Data:       no specific data for this command
+
+   Result:     OK - unsubscribe completed
+               NO - unsubscribe failure: can't unsubscribe that name
+               BAD - command unknown or arguments invalid
+
+      The UNSUBSCRIBE MAILBOX command is identical in effect to the
+      UNSUBSCRIBE command.  A server which implements this command must
+      be able to distinguish between a UNSUBSCRIBE MAILBOX command and
+      an UNSUBSCRIBE command with a mailbox name argument of "MAILBOX".
+
+   Example:    C: A002 UNSUBSCRIBE MAILBOX #news.comp.mail.mime
+               S: A002 OK UNSUBSCRIBE MAILBOX from #news.comp.mail.mime
+               completed
+               C: A003 UNSUBSCRIBE MAILBOX
+               S: A003 OK UNSUBSCRIBE from MAILBOX completed
+
+6.4.OBS.1       PARTIAL Command
+
+   Arguments:  message sequence number
+               message data item name
+               position of first octet
+               number of octets
+
+   Data:       untagged responses: FETCH
+
+   Result:     OK - partial completed
+               NO - partial error: can't fetch that data
+               BAD - command unknown or arguments invalid
+
+      The PARTIAL command is equivalent to the associated FETCH command,
+      with the added functionality that only the specified number of
+      octets, beginning at the specified starting octet, are returned.
+      Only a single message can be fetched at a time.  The first octet
+      of a message, and hence the minimum for the starting octet, is
+      octet 1.
+
+
+
+
+Crispin                      Informational                      [Page 3]
+
+RFC 2062                     IMAP4 Obsolete                December 1996
+
+
+      The following FETCH items are valid data for PARTIAL: RFC822,
+      RFC822.HEADER, RFC822.TEXT, BODY[<section>], as well as any .PEEK
+      forms of these.
+
+      Any partial fetch that attempts to read beyond the end of the text
+      is truncated as appropriate.  If the starting octet is beyond the
+      end of the text, an empty string is returned.
+
+      The data are returned with the FETCH response.  There is no
+      indication of the range of the partial data in this response.  It
+      is not possible to stream multiple PARTIAL commands of the same
+      data item without processing and synchronizing at each step, since
+      streamed commands may be executed out of order.
+
+      There is no requirement that partial fetches follow any sequence.
+      For example, if a partial fetch of octets 1 through 10000 breaks
+      in an awkward place for BASE64 decoding, it is permitted to
+      continue with a partial fetch of 9987 through 19987, etc.
+
+      The handling of the \Seen flag is the same as in the associated
+      FETCH command.
+
+   Example:    C: A005 PARTIAL 4 RFC822 1 1024
+               S: * 1 FETCH (RFC822 {1024}
+               S: Return-Path: <gray@cac.washington.edu>
+               S: ...
+               S: .........  FLAGS (\Seen))
+               S: A005 OK PARTIAL completed
+
+6.4.5.OBS.1     Obsolete FETCH Data Items
+
+   The following FETCH data items are obsolete:
+
+      BODY[<...>0]   A body part number of 0 is the [RFC-822] header of
+                     the message.  BODY[0] is functionally equivalent to
+                     BODY[HEADER], differing in the syntax of the
+                     resulting untagged FETCH data (BODY[0] is
+                     returned).
+
+      RFC822.HEADER.LINES <header_list>
+                     Functionally equivalent to BODY.PEEK[HEADER.LINES
+                     <header_list>], differing in the syntax of the
+                     resulting untagged FETCH data (RFC822.HEADER is
+                     returned).
+
+
+
+
+
+
+
+Crispin                      Informational                      [Page 4]
+
+RFC 2062                     IMAP4 Obsolete                December 1996
+
+
+      RFC822.HEADER.LINES.NOT <header_list>
+                     Functionally equivalent to
+                     BODY.PEEK[HEADER.LINES.NOT <header_list>],
+                     differing in the syntax of the resulting untagged
+                     FETCH data (RFC822.HEADER is returned).
+
+      RFC822.PEEK    Functionally equivalent to BODY.PEEK[], except for
+                     the syntax of the resulting untagged FETCH data
+                     (RFC822 is returned).
+
+      RFC822.TEXT.PEEK
+                     Functionally equivalent to BODY.PEEK[TEXT], except
+                     for the syntax of the resulting untagged FETCH data
+                     (RFC822.TEXT is returned).
+
+Obsolete Responses
+
+   The following responses are OBSOLETE.  Except as noted below, these
+   responses MUST NOT be transmitted by new server implementations.
+   Client implementations SHOULD accept these responses.
+
+   The section headings of these responses are intended to correspond
+   with where they would be located in the main document if they were
+   not obsoleted.
+
+7.2.OBS.1.      MAILBOX Response
+
+   Data:       name
+
+      The MAILBOX response MUST NOT be transmitted by server
+      implementations except in response to the obsolete FIND MAILBOXES
+      and FIND ALL.MAILBOXES commands.  Client implementations that do
+      not use these commands MAY ignore this response.  It is documented
+      here for the benefit of implementors who may wish to support it
+      for compatibility with old client implementations.
+
+      This response occurs as a result of the FIND MAILBOXES and FIND
+      ALL.MAILBOXES commands.  It returns a single name that matches the
+      FIND specification.  There are no attributes or hierarchy
+      delimiter.
+
+   Example:    S: * MAILBOX blurdybloop
+
+
+
+
+
+
+
+
+
+Crispin                      Informational                      [Page 5]
+
+RFC 2062                     IMAP4 Obsolete                December 1996
+
+
+7.3.OBS.1.      COPY Response
+
+   Data:       none
+
+      The COPY response MUST NOT be transmitted by new server
+      implementations.  Client implementations MUST ignore the COPY
+      response.  It is documented here for the benefit of client
+      implementors who may encounter this response from old server
+      implementations.
+
+      In some experimental versions of this protocol, this response was
+      returned in response to a COPY command to indicate on a
+      per-message basis that the message was copied successfully.
+
+   Example:    S: * 44 COPY
+
+7.3.OBS.2.      STORE Response
+
+   Data:       message data
+
+      The STORE response MUST NOT be transmitted by new server
+      implementations.  Client implementations MUST treat the STORE
+      response as equivalent to the FETCH response.  It is documented
+      here for the benefit of client implementors who may encounter this
+      response from old server implementations.
+
+      In some experimental versions of this protocol, this response was
+      returned instead of FETCH in response to a STORE command to report
+      the new value of the flags.
+
+   Example:    S: * 69 STORE (FLAGS (\Deleted))
+
+Formal Syntax of Obsolete Commands and Responses
+
+   Each obsolete syntax rule that is suffixed with "_old" is added to
+   the corresponding name in the formal syntax.  For example,
+   command_auth_old adds the FIND command to command_auth.
+
+   command_auth_old ::= find
+
+   command_select_old
+                   ::= partial
+
+   date_year_old   ::= 2digit
+                       ;; (year - 1900)
+
+   date_time_old   ::= <"> date_day_fixed "-" date_month "-" date_year
+                       SPACE time "-" zone_name <">
+
+
+
+Crispin                      Informational                      [Page 6]
+
+RFC 2062                     IMAP4 Obsolete                December 1996
+
+
+   find            ::= "FIND" SPACE ["ALL."] "MAILBOXES" SPACE
+                       list_mailbox
+
+   fetch_att_old   ::= "RFC822.HEADER.LINES" [".NOT"] SPACE header_list /
+                       fetch_text_old
+
+   fetch_text_old  ::= "BODY" [".PEEK"] section_old /
+                       "RFC822" [".HEADER" / ".TEXT" [".PEEK"]]
+
+   msg_data_old    ::= "COPY" / ("STORE" SPACE msg_att)
+
+   partial         ::= "PARTIAL" SPACE nz_number SPACE fetch_text_old SPACE
+                       number SPACE number
+
+   section_old     ::= "[" (number ["." number]) "]"
+
+   subscribe_old   ::= "SUBSCRIBE" SPACE "MAILBOX" SPACE mailbox
+
+   unsubscribe_old ::= "UNSUBSCRIBE" SPACE "MAILBOX" SPACE mailbox
+
+   zone_name       ::= "UT" / "GMT" / "Z" /                ;; +0000
+                       "AST" / "EDT" /                     ;; -0400
+                       "EST" / "CDT" /                     ;; -0500
+                       "CST" / "MDT" /                     ;; -0600
+                       "MST" / "PDT" /                     ;; -0700
+                       "PST" / "YDT" /                     ;; -0800
+                       "YST" / "HDT" /                     ;; -0900
+                       "HST" / "BDT" /                     ;; -1000
+                       "BST" /                             ;; -1100
+                       "A" / "B" / "C" / "D" / "E" / "F" / ;; +1 to +6
+                       "G" / "H" / "I" / "K" / "L" / "M" / ;; +7 to +12
+                       "N" / "O" / "P" / "Q" / "R" / "S" / ;; -1 to -6
+                       "T" / "U" / "V" / "W" / "X" / "Y"   ;; -7 to -12
+
+Security Considerations
+
+   Security issues are not discussed in this memo.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                      Informational                      [Page 7]
+
+RFC 2062                     IMAP4 Obsolete                December 1996
+
+
+Author's Address
+
+   Mark R. Crispin
+   Networks and Distributed Computing
+   University of Washington
+   4545 15th Aveneue NE
+   Seattle, WA  98105-4527
+
+   Phone: (206) 543-5762
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                      Informational                      [Page 8]
+
diff --git a/imap/docs/rfc/rfc2087.txt b/imap/docs/rfc/rfc2087.txt
new file mode 100644
index 00000000..1db5b57b
--- /dev/null
+++ b/imap/docs/rfc/rfc2087.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group                                           J. Myers
+Request for Comments: 2087                               Carnegie Mellon
+Category: Standards Track                                   January 1997
+
+
+                         IMAP4 QUOTA extension
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+1.   Abstract
+
+   The QUOTA extension of the Internet Message Access Protocol [IMAP4]
+   permits administrative limits on resource usage (quotas) to be
+   manipulated through the IMAP protocol.
+
+Table of Contents
+
+   1.   Abstract........................................... 1
+   2.   Conventions Used in this Document.................. 1
+   3.   Introduction and Overview.......................... 2
+   4.   Commands........................................... 2
+   4.1. SETQUOTA Command................................... 2
+   4.2. GETQUOTA Command................................... 2
+   4.3. GETQUOTAROOT Command............................... 3
+   5.   Responses.......................................... 3
+   5.1. QUOTA Response..................................... 3
+   5.2. QUOTAROOT Response................................. 4
+   6.   Formal syntax...................................... 4
+   7.   References......................................... 5
+   8.   Security Considerations............................ 5
+   9.   Author's Address................................... 5
+
+
+2.   Conventions Used in this Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.
+
+
+
+
+
+
+
+
+Myers                       Standards Track                     [Page 1]
+
+RFC 2087                         QUOTA                      January 1997
+
+
+3.   Introduction and Overview
+
+   The QUOTA extension is present in any IMAP4 implementation which
+   returns "QUOTA" as one of the supported capabilities to the
+   CAPABILITY command.
+
+   An IMAP4 server which supports the QUOTA capability may support
+   limits on any number of resources.  Each resource has an atom name
+   and an implementation-defined interpretation which evaluates to an
+   integer.  Examples of such resources are:
+
+      Name       Interpretation
+
+      STORAGE    Sum of messages' RFC822.SIZE, in units of 1024 octets
+      MESSAGE    Number of messages
+
+
+   Each mailbox has zero or more implementation-defined named "quota
+   roots".  Each quota root has zero or more resource limits.  All
+   mailboxes that share the same named quota root share the resource
+   limits of the quota root.
+
+   Quota root names do not necessarily have to match the names of
+   existing mailboxes.
+
+4.   Commands
+
+4.1. SETQUOTA Command
+
+   Arguments:  quota root
+               list of resource limits
+
+   Data:       untagged responses: QUOTA
+
+   Result:     OK - setquota completed
+               NO - setquota error: can't set that data
+               BAD - command unknown or arguments invalid
+
+   The SETQUOTA command takes the name of a mailbox quota root and a
+   list of resource limits. The resource limits for the named quota root
+   are changed to be the specified limits.  Any previous resource limits
+   for the named quota root are discarded.
+
+   If the named quota root did not previously exist, an implementation
+   may optionally create it and change the quota roots for any number of
+   existing mailboxes in an implementation-defined manner.
+
+
+
+
+
+Myers                       Standards Track                     [Page 2]
+
+RFC 2087                         QUOTA                      January 1997
+
+
+   Example:    C: A001 SETQUOTA "" (STORAGE 512)
+               S: * QUOTA "" (STORAGE 10 512)
+               S: A001 OK Setquota completed
+
+4.2. GETQUOTA Command
+
+   Arguments:  quota root
+
+   Data:       untagged responses: QUOTA
+
+   Result:     OK - getquota completed
+               NO - getquota  error:  no  such  quota  root,  permission
+               denied
+               BAD - command unknown or arguments invalid
+
+   The GETQUOTA command takes the name of a quota root and returns the
+   quota root's resource usage and limits in an untagged QUOTA response.
+
+   Example:    C: A003 GETQUOTA ""
+               S: * QUOTA "" (STORAGE 10 512)
+               S: A003 OK Getquota completed
+
+4.3. GETQUOTAROOT Command
+
+   Arguments:  mailbox name
+
+   Data:       untagged responses: QUOTAROOT, QUOTA
+
+   Result:     OK - getquota completed
+               NO - getquota error: no such mailbox, permission denied
+               BAD - command unknown or arguments invalid
+
+   The GETQUOTAROOT command takes the name of a mailbox and returns the
+   list of quota roots for the mailbox in an untagged QUOTAROOT
+   response.  For each listed quota root, it also returns the quota
+   root's resource usage and limits in an untagged QUOTA response.
+
+   Example:    C: A003 GETQUOTAROOT INBOX
+               S: * QUOTAROOT INBOX ""
+               S: * QUOTA "" (STORAGE 10 512)
+               S: A003 OK Getquota completed
+
+
+
+
+
+
+
+
+
+
+Myers                       Standards Track                     [Page 3]
+
+RFC 2087                         QUOTA                      January 1997
+
+
+5.   Responses
+
+5.1. QUOTA Response
+
+   Data:       quota root name
+               list of resource names, usages, and limits
+
+      This response occurs as a result of a GETQUOTA or GETQUOTAROOT
+      command. The first string is the name of the quota root for which
+      this quota applies.
+
+      The name is followed by a S-expression format list of the resource
+      usage and limits of the quota root.  The list contains zero or
+      more triplets.  Each triplet conatins a resource name, the current
+      usage of the resource, and the resource limit.
+
+      Resources not named in the list are not limited in the quota root.
+      Thus, an empty list means there are no administrative resource
+      limits in the quota root.
+
+      Example:    S: * QUOTA "" (STORAGE 10 512)
+
+5.2. QUOTAROOT Response
+
+   Data:       mailbox name
+               zero or more quota root names
+
+      This response occurs as a result of a GETQUOTAROOT command.  The
+      first string is the mailbox and the remaining strings are the
+      names of the quota roots for the mailbox.
+
+      Example:    S: * QUOTAROOT INBOX ""
+                  S: * QUOTAROOT comp.mail.mime
+
+6.   Formal syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (BNF) notation as specified in RFC 822 with one exception; the
+   delimiter used with the "#" construct is a single space (SP) and not
+   one or more commas.
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper or lower case characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+
+
+
+
+
+Myers                       Standards Track                     [Page 4]
+
+RFC 2087                         QUOTA                      January 1997
+
+
+   getquota        ::= "GETQUOTA" SP astring
+
+   getquotaroot    ::= "GETQUOTAROOT" SP astring
+
+   quota_list      ::= "(" #quota_resource ")"
+
+   quota_resource  ::= atom SP number SP number
+
+   quota_response  ::= "QUOTA" SP astring SP quota_list
+
+   quotaroot_response
+                   ::= "QUOTAROOT" SP astring *(SP astring)
+
+   setquota        ::= "SETQUOTA" SP astring SP setquota_list
+
+   setquota_list   ::= "(" 0#setquota_resource ")"
+
+   setquota_resource ::= atom SP number
+
+7.   References
+
+   [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4",
+   RFC 1730, University of Washington, December 1994.
+
+   [RFC-822] Crocker, D., "Standard for    the Format of ARPA Internet
+   Text Messages", STD 11, RFC 822.
+
+8.   Security Considerations
+
+   Implementors should be careful to make sure the implementation of
+   these commands does not violate the site's security policy. The
+   resource usage of other users is likely to be considered confidential
+   information and should not be divulged to unauthorized persons.
+
+9.   Author's Address
+
+   John G. Myers
+   Carnegie-Mellon University
+   5000 Forbes Ave.
+   Pittsburgh PA, 15213-3890
+
+   EMail: jgm+@cmu.edu
+
+
+
+
+
+
+
+
+
+Myers                       Standards Track                     [Page 5]
+
diff --git a/imap/docs/rfc/rfc2088.txt b/imap/docs/rfc/rfc2088.txt
new file mode 100644
index 00000000..f36cc764
--- /dev/null
+++ b/imap/docs/rfc/rfc2088.txt
@@ -0,0 +1,115 @@
+
+
+
+
+
+
+Network Working Group                                           J. Myers
+Request for Comments: 2088                               Carnegie Mellon
+Cateogry: Standards Track                                   January 1997
+
+
+                    IMAP4 non-synchronizing literals
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+1.   Abstract
+
+   The Internet Message Access Protocol [IMAP4] contains the "literal"
+   syntactic construct for communicating strings.  When sending a
+   literal from client to server, IMAP4 requires the client to wait for
+   the server to send a command continuation request between sending the
+   octet count and the string data.  This document specifies an
+   alternate form of literal which does not require this network round
+   trip.
+
+2.   Conventions Used in this Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.
+
+3.   Specification
+
+   The non-synchronizing literal is added an alternate form of literal,
+   and may appear in communication from client to server instead of the
+   IMAP4 form of literal.  The IMAP4 form of literal, used in
+   communication from client to server, is referred to as a
+   synchronizing literal.
+
+   Non-synchronizing literals may be used with any IMAP4 server
+   implementation which returns "LITERAL+" as one of the supported
+   capabilities to the CAPABILITY command.  If the server does not
+   advertise the LITERAL+ capability, the client must use synchronizing
+   literals instead.
+
+   The non-synchronizing literal is distinguished from the original
+   synchronizing literal by having a plus ('+') between the octet count
+   and the closing brace ('}').  The server does not generate a command
+   continuation request in response to a non-synchronizing literal, and
+
+
+
+Myers                       Standards Track                     [Page 1]
+
+RFC 2088                        LITERAL                     January 1997
+
+
+   clients are not required to wait before sending the octets of a non-
+   synchronizing literal.
+
+   The protocol receiver of an IMAP4 server must check the end of every
+   received line for an open brace ('{') followed by an octet count, a
+   plus ('+'), and a close brace ('}') immediately preceeding the CRLF.
+   If it finds this sequence, it is the octet count of a non-
+   synchronizing literal and the server MUST treat the specified number
+   of following octets and the following line as part of the same
+   command.  A server MAY still process commands and reject errors on a
+   line-by-line basis, as long as it checks for non-synchronizing
+   literals at the end of each line.
+
+   Example:    C: A001 LOGIN {11+}
+               C: FRED FOOBAR {7+}
+               C: fat man
+               S: A001 OK LOGIN completed
+
+4.   Formal Syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (BNF) notation as specified in [RFC-822] as modified by [IMAP4].
+   Non-terminals referenced but not defined below are as defined by
+   [IMAP4].
+
+   literal         ::= "{" number ["+"] "}" CRLF *CHAR8
+                       ;; Number represents the number of CHAR8 octets
+
+6.   References
+
+   [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4",
+   draft-crispin-imap-base-XX.txt, University of Washington, April 1996.
+
+   [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text
+   Messages", STD 11, RFC 822.
+
+7.   Security Considerations
+
+   There are no known security issues with this extension.
+
+8.   Author's Address
+
+   John G. Myers
+   Carnegie-Mellon University
+   5000 Forbes Ave.
+   Pittsburgh PA, 15213-3890
+
+   Email: jgm+@cmu.edu
+
+
+
+Myers                       Standards Track                     [Page 2]
+
diff --git a/imap/docs/rfc/rfc2177.txt b/imap/docs/rfc/rfc2177.txt
new file mode 100644
index 00000000..c11c7654
--- /dev/null
+++ b/imap/docs/rfc/rfc2177.txt
@@ -0,0 +1,227 @@
+
+
+
+
+
+
+Network Working Group                                           B. Leiba
+Request for Comments: 2177               IBM T.J. Watson Research Center
+Category: Standards Track                                      June 1997
+
+
+                           IMAP4 IDLE command
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+1.   Abstract
+
+   The Internet Message Access Protocol [IMAP4] requires a client to
+   poll the server for changes to the selected mailbox (new mail,
+   deletions).  It's often more desirable to have the server transmit
+   updates to the client in real time.  This allows a user to see new
+   mail immediately.  It also helps some real-time applications based on
+   IMAP, which might otherwise need to poll extremely often (such as
+   every few seconds).  (While the spec actually does allow a server to
+   push EXISTS responses aysynchronously, a client can't expect this
+   behaviour and must poll.)
+
+   This document specifies the syntax of an IDLE command, which will
+   allow a client to tell the server that it's ready to accept such
+   real-time updates.
+
+2.   Conventions Used in this Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.
+
+   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+   in this document are to be interpreted as described in RFC 2060
+   [IMAP4].
+
+3.   Specification
+
+   IDLE Command
+
+   Arguments:  none
+
+   Responses:  continuation data will be requested; the client sends
+               the continuation data "DONE" to end the command
+
+
+
+Leiba                       Standards Track                     [Page 1]
+
+RFC 2177                   IMAP4 IDLE command                  June 1997
+
+
+
+   Result:     OK - IDLE completed after client sent "DONE"
+               NO - failure: the server will not allow the IDLE
+                    command at this time
+              BAD - command unknown or arguments invalid
+
+   The IDLE command may be used with any IMAP4 server implementation
+   that returns "IDLE" as one of the supported capabilities to the
+   CAPABILITY command.  If the server does not advertise the IDLE
+   capability, the client MUST NOT use the IDLE command and must poll
+   for mailbox updates.  In particular, the client MUST continue to be
+   able to accept unsolicited untagged responses to ANY command, as
+   specified in the base IMAP specification.
+
+   The IDLE command is sent from the client to the server when the
+   client is ready to accept unsolicited mailbox update messages.  The
+   server requests a response to the IDLE command using the continuation
+   ("+") response.  The IDLE command remains active until the client
+   responds to the continuation, and as long as an IDLE command is
+   active, the server is now free to send untagged EXISTS, EXPUNGE, and
+   other messages at any time.
+
+   The IDLE command is terminated by the receipt of a "DONE"
+   continuation from the client; such response satisfies the server's
+   continuation request.  At that point, the server MAY send any
+   remaining queued untagged responses and then MUST immediately send
+   the tagged response to the IDLE command and prepare to process other
+   commands. As in the base specification, the processing of any new
+   command may cause the sending of unsolicited untagged responses,
+   subject to the ambiguity limitations.  The client MUST NOT send a
+   command while the server is waiting for the DONE, since the server
+   will not be able to distinguish a command from a continuation.
+
+   The server MAY consider a client inactive if it has an IDLE command
+   running, and if such a server has an inactivity timeout it MAY log
+   the client off implicitly at the end of its timeout period.  Because
+   of that, clients using IDLE are advised to terminate the IDLE and
+   re-issue it at least every 29 minutes to avoid being logged off.
+   This still allows a client to receive immediate mailbox updates even
+   though it need only "poll" at half hour intervals.
+
+
+
+
+
+
+
+
+
+
+
+Leiba                       Standards Track                     [Page 2]
+
+RFC 2177                   IMAP4 IDLE command                  June 1997
+
+
+   Example:    C: A001 SELECT INBOX
+               S: * FLAGS (Deleted Seen)
+               S: * 3 EXISTS
+               S: * 0 RECENT
+               S: * OK [UIDVALIDITY 1]
+               S: A001 OK SELECT completed
+               C: A002 IDLE
+               S: + idling
+               ...time passes; new mail arrives...
+               S: * 4 EXISTS
+               C: DONE
+               S: A002 OK IDLE terminated
+               ...another client expunges message 2 now...
+               C: A003 FETCH 4 ALL
+               S: * 4 FETCH (...)
+               S: A003 OK FETCH completed
+               C: A004 IDLE
+               S: * 2 EXPUNGE
+               S: * 3 EXISTS
+               S: + idling
+               ...time passes; another client expunges message 3...
+               S: * 3 EXPUNGE
+               S: * 2 EXISTS
+               ...time passes; new mail arrives...
+               S: * 3 EXISTS
+               C: DONE
+               S: A004 OK IDLE terminated
+               C: A005 FETCH 3 ALL
+               S: * 3 FETCH (...)
+               S: A005 OK FETCH completed
+               C: A006 IDLE
+
+4.   Formal Syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (BNF) notation as specified in [RFC-822] as modified by [IMAP4].
+   Non-terminals referenced but not defined below are as defined by
+   [IMAP4].
+
+   command_auth    ::= append / create / delete / examine / list / lsub /
+                       rename / select / status / subscribe / unsubscribe
+                       / idle
+                       ;; Valid only in Authenticated or Selected state
+
+   idle            ::= "IDLE" CRLF "DONE"
+
+
+
+
+
+
+Leiba                       Standards Track                     [Page 3]
+
+RFC 2177                   IMAP4 IDLE command                  June 1997
+
+
+5.   References
+
+   [IMAP4] Crispin, M., "Internet Message Access Protocol - Version
+   4rev1", RFC 2060, December 1996.
+
+6.   Security Considerations
+
+   There are no known security issues with this extension.
+
+7.   Author's Address
+
+   Barry Leiba
+   IBM T.J. Watson Research Center
+   30 Saw Mill River Road
+   Hawthorne, NY  10532
+
+   Email: leiba@watson.ibm.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Leiba                       Standards Track                     [Page 4]
+
diff --git a/imap/docs/rfc/rfc2180.txt b/imap/docs/rfc/rfc2180.txt
new file mode 100644
index 00000000..57607002
--- /dev/null
+++ b/imap/docs/rfc/rfc2180.txt
@@ -0,0 +1,787 @@
+
+
+
+
+
+
+Network Working Group                                          M. Gahrns
+Request for Comments: 2180                                     Microsoft
+Category: Informational                                        July 1997
+
+
+                 IMAP4 Multi-Accessed Mailbox Practice
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  This memo
+   does not specify an Internet standard of any kind.  Distribution of
+   this memo is unlimited.
+
+1. Abstract
+
+   IMAP4[RFC-2060] is rich client/server protocol that allows a client
+   to access and manipulate electronic mail messages on a server.
+   Within the protocol framework, it is possible to have differing
+   results for particular client/server interactions. If a protocol does
+   not allow for this, it is often unduly restrictive.
+
+   For example, when multiple clients are accessing a mailbox and one
+   attempts to delete the mailbox, an IMAP4 server may choose to
+   implement a solution based upon server architectural constraints or
+   individual preference.
+
+   With this flexibility comes greater client responsibility.  It is not
+   sufficient for a client to be written based upon the behavior of a
+   particular IMAP server.  Rather the client must be based upon the
+   behavior allowed by the protocol.
+
+   By documenting common IMAP4 server practice for the case of
+   simultaneous client access to a mailbox, we hope to ensure the widest
+   amount of inter-operation between IMAP4 clients and servers.
+
+   The behavior described in this document reflects the practice of some
+   existing servers or behavior that the consensus of the IMAP mailing
+   list has deemed to be reasonable.  The behavior described within this
+   document is believed to be [RFC-2060] compliant. However, this
+   document is not meant to define IMAP4 compliance, nor is it an
+   exhaustive list of valid IMAP4 behavior. [RFC-2060] must always be
+   consulted to determine IMAP4 compliance, especially for server
+   behavior not described within this document.
+
+
+
+
+
+
+
+
+Gahrns                       Informational                      [Page 1]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+2. Conventions used in this document
+
+   In examples,"C1:", "C2:" and "C3:" indicate lines sent by 3 different
+   clients (client #1, client #2 and client #3) that are connected to a
+   server.  "S1:", "S2:" and "S3:" indicated lines sent by the server to
+   client #1, client #2 and client #3 respectively.
+
+   A shared mailbox, is a mailbox that can be used by multiple users.
+
+   A multi-accessed mailbox, is a mailbox that has multiple clients
+   simultaneously accessing it.
+
+   A client is said to have accessed a mailbox after a successful SELECT
+   or EXAMINE command.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC-2119].
+
+
+3. Deletion/Renaming of a multi-accessed mailbox
+
+   If an external agent or multiple clients are accessing a mailbox,
+   care must be taken when handling the deletion or renaming of the
+   mailbox. Following are some strategies an IMAP server may choose to
+   use when dealing with this situation.
+
+
+3.1. The server MAY fail the DELETE/RENAME command of a multi-accessed
+     mailbox
+
+   In some cases, this behavior may not be practical.  For example, if a
+   large number of clients are accessing a shared mailbox, the window in
+   which no clients have the mailbox accessed may be small or non-
+   existent, effectively rendering the mailbox undeletable or
+   unrenamable.
+
+   Example:
+
+   <Client #1 and Client #2 have mailbox FOO accessed. Client #1 tries
+   to DELETE the mailbox and is refused>
+
+             C1: A001 DELETE FOO
+             S1: A001 NO Mailbox FOO is in use by another user.
+
+
+
+
+
+
+
+Gahrns                       Informational                      [Page 2]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+3.2. The server MAY allow the DELETE command of a multi-accessed
+     mailbox, but keep the information in the mailbox available for
+     those clients that currently have access to the mailbox.
+
+   When all clients have finished accessing the mailbox, it is
+   permanently removed.  For clients that do not already have access to
+   the mailbox, the 'ghosted' mailbox would not be available.  For
+   example, it would not be returned to these clients in a subsequent
+   LIST or LSUB command and would not be a valid mailbox argument to any
+   other IMAP command until the reference count of clients accessing the
+   mailbox reached 0.
+
+   In some cases, this behavior may not be desirable. For example if
+   someone created a mailbox with offensive or sensitive information,
+   one might prefer to have the mailbox deleted and all access to the
+   information contained within removed immediately, rather than
+   continuing to allow access until the client closes the mailbox.
+
+   Furthermore, this behavior, may prevent 'recycling' of the same
+   mailbox name until all clients have finished accessing the original
+   mailbox.
+
+   Example:
+
+   <Client #1 and Client #2 have mailbox FOO selected. Client #1 DELETEs
+   mailbox FOO>
+
+             C1: A001 DELETE FOO
+             S1: A001 OK Mailbox FOO is deleted.
+
+   <Client #2 is still able to operate on the deleted mailbox>
+
+             C2: B001 STORE 1 +FLAGS (\Seen)
+             S2: * 1 FETCH FLAGS (\Seen)
+             S2: B001 OK STORE completed
+
+   <Client #3 which did not have access to the mailbox prior to the
+   deletion by client #1 does not have access to the mailbox>
+
+             C3: C001 STATUS FOO (MESSAGES)
+             S3: C001 NO Mailbox does not exist
+
+   <Nor is client #3 able to create a mailbox with the name FOO, while
+   the reference count is non zero>
+
+             C3: C002 CREATE FOO
+             S3: C002 NO Mailbox FOO is still in use. Try again later.
+
+
+
+
+Gahrns                       Informational                      [Page 3]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+   <Client #2 closes its access to the mailbox, no other clients have
+   access to the mailbox FOO and reference count becomes 0>
+
+             C2: B002 CLOSE
+             S2: B002 OK CLOSE Completed
+
+   <Now that the reference count on FOO has reached 0, the mailbox name
+   can be recycled>
+
+             C3: C003 CREATE FOO
+             S3: C003 OK CREATE Completed
+
+
+3.3. The server MAY allow the DELETE/RENAME of a multi-accessed
+     mailbox, but disconnect all other clients who have the mailbox
+     accessed by sending a untagged BYE response.
+
+   A server may often choose to disconnect clients in the DELETE case,
+   but may choose to implement a "friendlier" method for the RENAME
+   case.
+
+   Example:
+
+   <Client #1 and Client #2 have mailbox FOO accessed. Client #1 DELETEs
+   the mailbox FOO>
+
+             C1: A002 DELETE FOO
+             S1: A002 OK DELETE completed.
+
+   <Server disconnects all other users of the mailbox>
+             S2: * BYE Mailbox FOO has been deleted.
+
+
+3.4. The server MAY allow the RENAME of a multi-accessed mailbox by
+     simply changing the name attribute on the mailbox.
+
+   Other clients that have access to the mailbox can continue issuing
+   commands such as FETCH that do not reference the mailbox name.
+   Clients would discover the renaming the next time they referred to
+   the old mailbox name.  Some servers MAY choose to include the
+   [NEWNAME] response code in their tagged NO response to a command that
+   contained the old mailbox name, as a hint to the client that the
+   operation can succeed if the command is issued with the new mailbox
+   name.
+
+
+
+
+
+
+
+Gahrns                       Informational                      [Page 4]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+   Example:
+
+   <Client #1 and Client #2 have mailbox FOO accessed. Client #1 RENAMEs
+   the mailbox.>
+
+             C1: A001 RENAME FOO BAR
+             S1: A001 OK RENAME completed.
+
+   <Client #2 is still able to do operations that do not reference the
+   mailbox name>
+
+             C2: B001 FETCH 2:4 (FLAGS)
+             S2: * 2 FETCH . . .
+             S2: * 3 FETCH . . .
+             S2: * 4 FETCH . . .
+             S2: B001 OK FETCH completed
+
+   <Client #2 is not able to do operations that reference the mailbox
+   name>
+
+             C2: B002 APPEND FOO {300} C2: Date: Mon, 7 Feb 1994
+             21:52:25 0800 (PST) C2: . . .  S2: B002 NO [NEWNAME FOO
+             BAR] Mailbox has been renamed
+
+
+4. Expunging of messages on a multi-accessed mailbox
+
+   If an external agent or multiple clients are accessing a mailbox,
+   care must be taken when handling the EXPUNGE of messages.  Other
+   clients accessing the mailbox may be in the midst of issuing a
+   command that depends upon message sequence numbers.  Because an
+   EXPUNGE response can not be sent while responding to a FETCH, STORE
+   or SEARCH command, it is not possible to immediately notify the
+   client of the EXPUNGE.  This can result in ambiguity if the client
+   issues a FETCH, STORE or SEARCH operation on a message that has been
+   EXPUNGED.
+
+
+4.1. Fetching of expunged messages
+
+   Following are some strategies an IMAP server may choose to use when
+   dealing with a FETCH command on expunged messages.
+
+
+
+
+
+
+
+
+
+Gahrns                       Informational                      [Page 5]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+   Consider the following scenario:
+
+   - Client #1 and Client #2 have mailbox FOO selected.
+   - There are 7 messages in the mailbox.
+   - Messages 4:7 are marked for deletion.
+   - Client #1 issues an EXPUNGE, to expunge messages 4:7
+
+
+4.1.1. The server MAY allow the EXPUNGE of a multi-accessed mailbox but
+       keep the messages available to satisfy subsequent FETCH commands
+       until it is able to send an EXPUNGE response to each client.
+
+   In some cases, the behavior of keeping "ghosted" messages may not be
+   desirable.  For example if a message contained offensive or sensitive
+   information, one might prefer to instantaneously remove all access to
+   the information, regardless of whether another client is in the midst
+   of accessing it.
+
+   Example:  (Building upon the scenario outlined in 4.1.)
+
+   <Client #2 is still able to access the expunged messages because the
+   server has kept a 'ghosted' copy of the messages until it is able to
+   notify client #2 of the EXPUNGE>
+
+             C2: B001 FETCH 4:7 RFC822
+             S2: * 4 FETCH RFC822 . . . (RFC822 info returned)
+             S2: * 5 FETCH RFC822 . . . (RFC822 info returned)
+             S2: * 6 FETCH RFC822 . . . (RFC822 info returned)
+             S2: * 7 FETCH RFC822 . . . (RFC822 info returned)
+             S2: B001 OK FETCH Completed
+
+   <Client #2 issues a command where it can get notified of the EXPUNGE>
+
+             C2: B002 NOOP
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 3 EXISTS
+             S2: B002 OK NOOP Complete
+
+   <Client #2 no longer has access to the expunged messages>
+
+             C2: B003 FETCH 4:7 RFC822
+             S2: B003 NO Messages 4:7 are no longer available.
+
+
+
+
+
+
+Gahrns                       Informational                      [Page 6]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+4.1.2 The server MAY allow the EXPUNGE of a multi-accessed mailbox,
+      and on subsequent FETCH commands return FETCH responses only for
+      non-expunged messages and a tagged NO.
+
+   After receiving a tagged NO FETCH response, the client SHOULD issue a
+   NOOP command so that it will be informed of any pending EXPUNGE
+   responses.  The client may then either reissue the failed FETCH
+   command, or by examining the EXPUNGE response from the NOOP and the
+   FETCH response from the FETCH, determine that the FETCH failed
+   because of pending expunges.
+
+   Example:  (Building upon the scenario outlined in 4.1.)
+
+   <Client #2 attempts to FETCH a mix of expunged and non-expunged
+   messages.  A FETCH response is returned only for then non-expunged
+   messages along with a tagged NO>
+
+             C2: B001 FETCH 3:5 ENVELOPE
+             S2: * 3 FETCH ENVELOPE . . . (ENVELOPE info returned)
+             S2: B001 NO Some of the requested messages no longer exist
+
+   <Upon receiving a tagged NO FETCH response, Client #2 issues a NOOP
+   to be informed of any pending EXPUNGE responses>
+
+             C2: B002 NOOP
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 3 EXISTS
+             S2: B002 OK NOOP Completed.
+
+   <By receiving a FETCH response for message 3, and an EXPUNGE response
+   that indicates messages 4:7 have been expunged, the client does not
+   need to re-issue the FETCH>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns                       Informational                      [Page 7]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+4.1.3 The server MAY allow the EXPUNGE of a multi-accessed mailbox, and
+      on subsequent FETCH commands return the usual FETCH responses for
+      non-expunged messages, "NIL FETCH Responses" for expunged
+      messages, and a tagged OK response.
+
+   If all of the messages in the subsequent FETCH command have been
+   expunged, the server SHOULD return only a tagged NO.  In this case,
+   the client SHOULD issue a NOOP command so that it will be informed of
+   any pending EXPUNGE responses.  The client may then either reissue
+   the failed FETCH command, or by examining the EXPUNGE response from
+   the NOOP, determine that the FETCH failed because of pending
+   expunges.
+
+   "NIL FETCH responses" are a representation of empty data as
+   appropriate for the FETCH argument specified.
+
+   Example:
+
+   * 1 FETCH (ENVELOPE (NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL))
+   * 1 FETCH (FLAGS ())
+   * 1 FETCH (INTERNALDATE "00-Jan-0000 00:00:00 +0000")
+   * 1 FETCH (RFC822 "")
+   * 1 FETCH (RFC822.HEADER "")
+   * 1 FETCH (RFC822.TEXT "")
+   * 1 FETCH (RFC822.SIZE 0)
+   * 1 FETCH (BODY ("TEXT" "PLAIN" NIL NIL NIL "7BIT" 0 0)
+   * 1 FETCH (BODYSTRUCTURE ("TEXT" "PLAIN" NIL NIL NIL "7BIT" 0 0)
+   * 1 FETCH (BODY[<section>] "")
+   * 1 FETCH (BODY[<section>]<partial> "")
+
+   In some cases, a client may not be able to distinguish between "NIL
+   FETCH responses" received because a message was expunged and those
+   received because the data actually was NIL.  For example, a  * 5
+   FETCH (FLAGS ()) response could be received if no flags were set on
+   message 5, or because message 5 was expunged. In a case of potential
+   ambiguity, the client SHOULD issue a command such as NOOP to force
+   the sending of the EXPUNGE responses to resolve any ambiguity.
+
+   Example:  (Building upon the scenario outlined in 4.1.)
+
+   <Client #2 attempts to access a mix of expunged and non-expunged
+   messages.  Normal data is returned for non-expunged message, "NIL
+   FETCH responses" are returned for expunged messages>
+
+
+
+
+
+
+
+
+Gahrns                       Informational                      [Page 8]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+             C2: B002 FETCH 3:5 ENVELOPE
+             S2: * 3 FETCH ENVELOPE . . . (ENVELOPE info returned)
+             S2: * 4 FETCH ENVELOPE (NIL NIL NIL NIL NIL NIL NIL NIL
+                   NIL NIL)
+             S2: * 5 FETCH ENVELOPE (NIL NIL NIL NIL NIL NIL NIL NIL
+                   NIL NIL)
+             S2: B002 OK FETCH Completed
+
+   <Client #2 attempts to FETCH only expunged messages and receives a
+   tagged NO response>
+
+             C2: B002 FETCH 4:7 ENVELOPE
+             S2: B002 NO Messages 4:7 have been expunged.
+
+
+4.1.4 To avoid the situation altogether, the server MAY fail the
+      EXPUNGE of a multi-accessed mailbox
+
+   In some cases, this behavior may not be practical.  For example, if a
+   large number of clients are accessing a shared mailbox, the window in
+   which no clients have the mailbox accessed may be small or non-
+   existent, effectively rendering the message unexpungeable.
+
+
+4.2. Storing of expunged messages
+
+   Following are some strategies an IMAP server may choose to use when
+   dealing with a STORE command on expunged messages.
+
+
+4.2.1 If the ".SILENT" suffix is used, and the STORE completed
+      successfully for all the non-expunged messages, the server SHOULD
+      return a tagged OK.
+
+   Example:  (Building upon the scenario outlined in 4.1.)
+
+   <Client #2 tries to silently STORE flags on expunged and non-
+   expunged messages.  The server sets the flags on the non-expunged
+   messages and returns OK>
+
+             C2: B001 STORE 1:7 +FLAGS.SILENT (\SEEN)
+             S2: B001 OK
+
+
+
+
+
+
+
+
+
+Gahrns                       Informational                      [Page 9]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+4.2.2. If the ".SILENT" suffix is not used, and only expunged messages
+       are referenced, the server SHOULD return only a tagged NO.
+
+   Example:  (Building upon the scenario outlined in 4.1.)
+
+   <Client #2 tries to STORE flags only on expunged messages>
+
+             C2: B001 STORE 5:7 +FLAGS (\SEEN)
+             S2: B001 NO  Messages have been expunged
+
+
+4.2.3. If the ".SILENT" suffix is not used, and a mixture of expunged
+       and non-expunged messages are referenced, the server MAY set the
+       flags and return a FETCH response for the non-expunged messages
+       along with a tagged NO.
+
+   After receiving a tagged NO STORE response, the client SHOULD issue a
+   NOOP command so that it will be informed of any pending EXPUNGE
+   responses.  The client may then either reissue the failed STORE
+   command, or by examining the EXPUNGE responses from the NOOP and
+   FETCH responses from the STORE, determine that the STORE failed
+   because of pending expunges.
+
+   Example:  (Building upon the scenario outlined in 4.1.)
+
+   <Client #2 tries to STORE flags on a mixture of expunged and non-
+   expunged messages>
+
+             C2: B001 STORE 1:7 +FLAGS (\SEEN)
+             S2: * FETCH 1 FLAGS (\SEEN)
+             S2: * FETCH 2 FLAGS (\SEEN)
+             S2: * FETCH 3 FLAGS (\SEEN)
+             S2: B001 NO Some of the messages no longer exist.
+
+             C2: B002 NOOP
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 3 EXISTS
+             S2: B002 OK NOOP Completed.
+
+   <By receiving FETCH responses for messages 1:3, and an EXPUNGE
+   response that indicates messages 4:7 have been expunged, the client
+   does not need to re-issue the STORE>
+
+
+
+
+
+
+Gahrns                       Informational                     [Page 10]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+4.2.4. If the ".SILENT" suffix is not used, and a mixture of expunged
+       and non-expunged messages are referenced, the server MAY return
+       an untagged NO and not set any flags.
+
+   After receiving a tagged NO STORE response, the client SHOULD issue a
+   NOOP command so that it will be informed of any pending EXPUNGE
+   responses.  The client would then re-issue the STORE command after
+   updating its message list per any EXPUNGE response.
+
+   If a large number of clients are accessing a shared mailbox, the
+   window in which there are no pending expunges may be small or non-
+   existent, effectively disallowing a client from setting the flags on
+   all messages at once.
+
+   Example:  (Building upon the scenario outlined in 4.1.)
+
+   <Client #2 tries to STORE flags on a mixture of expunged and non-
+   expunged messages>
+
+             C2: B001 STORE 1:7 +FLAGS (\SEEN)
+             S2: B001 NO  Some of the messages no longer exist.
+
+   <Client #2 issues a NOOP to be informed of the EXPUNGED messages>
+
+             C2: B002 NOOP
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 4 EXPUNGE
+             S2: * 3 EXISTS
+             S2: B002 OK NOOP Completed.
+
+   <Client #2 updates its message list and re-issues the STORE on only
+   those messages that have not been expunged>
+
+             C2: B003 STORE 1:3 +FLAGS (\SEEN) S2: * FETCH 1 FLAGS
+             (\SEEN) S2: * FETCH 2 FLAGS (\SEEN) S2: * FETCH 3 FLAGS
+             (\SEEN) S2: B003 OK  STORE Completed
+
+
+4.3. Searching of expunged messages
+
+   A server MAY simply not return a search response for messages that
+   have been expunged and it has not been able to inform the client
+   about.  If a client was expecting a particular message to be returned
+   in a search result, and it was not, the client SHOULD issue a NOOP
+   command to see if the message was expunged by another client.
+
+
+
+
+Gahrns                       Informational                     [Page 11]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+4.4 Copying of expunged messages
+
+   COPY is the only IMAP4 sequence number command that is safe to allow
+   an EXPUNGE response on.  This is because a client is not permitted to
+   cascade several COPY commands together. A client is required to wait
+   and confirm that the copy worked before issuing another one.
+
+4.4.1 The server MAY disallow the COPY of messages in a multi-access
+      mailbox that contains expunged messages.
+
+   Pending EXPUNGE response(s) MUST be returned to the COPY command.
+
+   Example:
+
+             C: A001 COPY 2,4,6,8 FRED
+             S: * 4 EXPUNGE
+             S: A001 NO COPY rejected, because some of the requested
+                messages were expunged
+
+   Note: Non of the above messages are copied because if a COPY command
+   is unsuccessful, the server MUST restore the destination mailbox to
+   its state before the COPY attempt.
+
+
+4.4.2 The server MAY allow the COPY of messages in a multi-access
+      mailbox that contains expunged messages.
+
+   Pending EXPUNGE response(s) MUST be returned to the COPY command.
+   Messages that are copied are messages corresponding to sequence
+   numbers before any EXPUNGE response.
+
+   Example:
+
+             C: A001 COPY 2,4,6,8 FRED
+             S: * 3 EXPUNGE
+             S: A001 OK COPY completed
+
+   In the above example, the messages that are copied to FRED are
+   messages 2,4,6,8 at the start of the COPY command.  These are
+   equivalent to messages 2,3,5,7 at the end of the COPY command.  The
+   EXPUNGE response can't take place until after the messages from the
+   COPY command are identified (because of the "no expunge while no
+   commands in progress" rule).
+
+
+
+
+
+
+
+
+Gahrns                       Informational                     [Page 12]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+   Example:
+
+             C: A001 COPY 2,4,6,8 FRED
+             S: * 4 EXPUNGE
+             S: A001 OK COPY completed
+
+   In the above example, message 4 was copied before it was expunged,
+   and MUST appear in the destination mailbox FRED.
+
+
+5. Security Considerations
+
+   This document describes behavior of servers that use the IMAP4
+   protocol, and as such, has the same security considerations as
+   described in [RFC-2060].
+
+   In particular, some described server behavior does not allow for the
+   immediate deletion of information when a mailbox is accessed by
+   multiple clients.  This may be a consideration when dealing with
+   sensitive information where immediate deletion would be preferred.
+
+
+6. References
+
+   [RFC-2060], Crispin, M., "Internet Message Access Protocol - Version
+   4rev1", RFC 2060, University of Washington, December 1996.
+
+   [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
+   Requirement Levels", RFC 2119, Harvard University, March 1997.
+
+
+7.  Acknowledgments
+
+   This document is the result of discussions on the IMAP4 mailing list
+   and is meant to reflect consensus of this group.  In particular,
+   Raymond Cheng, Mark Crispin, Jim Evans, Erik Forsberg, Steve Hole,
+   Mark Keasling, Barry Leiba, Syd Logan, John Mani, Pat Moran, Larry
+   Osterman, Chris Newman, Bart Schaefer, Vladimir Vulovic, and Jack De
+   Winter were active participants in this discussion or made
+   suggestions to this document.
+
+
+
+
+
+
+
+
+
+
+
+Gahrns                       Informational                     [Page 13]
+
+RFC 2180         IMAP4 Multi-Accessed Mailbox Practice         July 1997
+
+
+8. Author's Address
+
+   Mike Gahrns
+   Microsoft
+   One Microsoft Way
+   Redmond, WA, 98072
+
+   Phone: (206) 936-9833
+   EMail: mikega@microsoft.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
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+
+
+
+
+
+
+
+
+
+Gahrns                       Informational                     [Page 14]
+
diff --git a/imap/docs/rfc/rfc2193.txt b/imap/docs/rfc/rfc2193.txt
new file mode 100644
index 00000000..2fec58d7
--- /dev/null
+++ b/imap/docs/rfc/rfc2193.txt
@@ -0,0 +1,507 @@
+
+
+
+
+
+
+Network Working Group                                        M. Gahrns
+Request for Comments: 2193                                   Microsoft
+Category: Standards Track                               September 1997
+
+
+                        IMAP4 Mailbox Referrals
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+1. Abstract
+
+   When dealing with large amounts of users, messages and geographically
+   dispersed IMAP4 [RFC-2060] servers, it is often desirable to
+   distribute messages amongst different servers within an organization.
+   For example an administrator may choose to store user's personal
+   mailboxes on a local IMAP4 server, while storing shared mailboxes
+   remotely on another server.  This type of configuration is common
+   when it is uneconomical to store all data centrally due to limited
+   bandwidth or disk resources.
+
+   Mailbox referrals allow clients to seamlessly access mailboxes that
+   are distributed across several IMAP4 servers.
+
+   A referral mechanism can provide efficiencies over the alternative
+   "proxy method", in which the local IMAP4 server contacts the remote
+   server on behalf of the client, and then transfers the data from the
+   remote server to itself, and then on to the client.  The referral
+   mechanism's direct client connection to the remote server is often a
+   more efficient use of bandwidth, and does not require the local
+   server to impersonate the client when authenticating to the remote
+   server.
+
+2. Conventions used in this document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.
+
+   A home server, is an IMAP4 server that contains the user's inbox.
+
+   A remote mailbox is a mailbox that is not hosted on the user's home
+   server.
+
+
+
+
+Gahrns                      Standards Track                     [Page 1]
+
+RFC 2193                IMAP4 Mailbox Referrals           September 1997
+
+
+   A remote server is a server that contains remote mailboxes.
+
+   A shared mailbox, is a mailbox that multiple users have access to.
+
+   An IMAP mailbox referral is when the server directs the client to
+   another IMAP mailbox.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC-2119].
+
+3. Introduction and Overview
+
+   IMAP4 servers that support this extension MUST list the keyword
+   MAILBOX-REFERRALS in their CAPABILITY response.  No client action is
+   needed to invoke the MAILBOX-REFERRALS capability in a server.
+
+   A MAILBOX-REFERRALS capable IMAP4 server MUST NOT return referrals
+   that result in a referrals loop.
+
+   A referral response consists of a tagged NO response and a REFERRAL
+   response code.  The REFERRAL response code MUST contain as an
+   argument a one or more valid URLs separated by a space as defined in
+   [RFC-1738]. If a server replies with multiple URLs for a particular
+   object, they MUST all be of the same type. In this case, the URL MUST
+   be an IMAP URL as defined in [RFC-2192].  A client that supports the
+   REFERRALS extension MUST be prepared for a URL of any type, but it
+   need only be able to process IMAP URLs.
+
+   A server MAY respond with multiple IMAP mailbox referrals if there is
+   more than one replica of the mailbox.  This allows the implementation
+   of a load balancing or failover scheme. How a server keeps multiple
+   replicas of a mailbox in sync is not addressed by this document.
+
+   If the server has a preferred order in which the client should
+   attempt to access the URLs, the preferred URL SHOULD be listed in the
+   first, with the remaining URLs presented in descending order of
+   preference.  If multiple referrals are given for a mailbox, a server
+   should be aware that there are synchronization issues for a client if
+   the UIDVALIDITY of the referred mailboxes are different.
+
+   An IMAP mailbox referral may be given in response to an IMAP command
+   that specifies a mailbox as an argument.
+
+
+
+
+
+
+
+
+Gahrns                      Standards Track                     [Page 2]
+
+RFC 2193                IMAP4 Mailbox Referrals           September 1997
+
+
+   Example:
+
+      A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/REMOTE]Remote Mailbox
+
+   NOTE: user;AUTH=* is specified as required by [RFC-2192] to avoid a
+   client falling back to anonymous login.
+
+   Remote mailboxes and their inferiors, that are accessible only via
+   referrals SHOULD NOT appear in LIST and LSUB responses issued against
+   the user's home server.  They MUST appear in RLIST and RLSUB
+   responses issued against the user's home server. Hierarchy referrals,
+   in which a client would be required to connect to the remote server
+   to issue a LIST to discover the inferiors of a mailbox are not
+   addressed in this document.
+
+   For example, if shared mailboxes were only accessible via referrals
+   on a remote server, a RLIST "" "#SHARED/%" command would return the
+   same response if issued against the user's home server or the remote
+   server.
+
+   Note: Mailboxes that are available on the user's home server do not
+   need to be available on the remote server.  In addition, there may be
+   additional mailboxes available on the remote server, but they will
+   not accessible to the client via referrals unless they appear in the
+   LIST response to the RLIST command against the user's home server.
+
+   A MAILBOX-REFERRALS capable client will issue the RLIST and RLSUB
+   commands in lieu of LIST and LSUB.  The RLIST and RLSUB commands
+   behave identically to their LIST and LSUB counterparts, except remote
+   mailboxes are returned in addition to local mailboxes in the LIST and
+   LSUB responses.  This avoids displaying to a non MAILBOX-REFERRALS
+   enabled client inaccessible remote mailboxes.
+
+4.1. SELECT, EXAMINE, DELETE, SUBSCRIBE, UNSUBSCRIBE, STATUS and APPEND
+     Referrals
+
+   An IMAP4 server MAY respond to the SELECT, EXAMINE, DELETE,
+   SUBSCRIBE, UNSUBSCRIBE, STATUS or APPEND command with one or more
+   IMAP mailbox referrals to indicate to the client that the mailbox is
+   hosted on a remote server.
+
+   When a client processes an IMAP mailbox referral, it will open a new
+   connection or use an existing connection to the remote server so that
+   it is able to issue the commands necessary to process the remote
+   mailbox.
+
+
+
+
+
+
+Gahrns                      Standards Track                     [Page 3]
+
+RFC 2193                IMAP4 Mailbox Referrals           September 1997
+
+
+   Example:  <IMAP4 connection to home server>
+
+      C: A001 DELETE "SHARED/FOO"
+      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/FOO]
+             Remote mailbox. Try SERVER2.
+
+      <Client established a second connection to SERVER2 and
+      issues the DELETE command on the referred mailbox>
+
+      S: * OK IMAP4rev1 server ready
+      C: B001 AUTHENTICATE KERBEROS_V4
+      <authentication exchange>
+      S: B001 OK user is authenticated
+
+      C: B002 DELETE "SHARED/FOO"
+      S: B002 OK DELETE completed
+
+   Example:  <IMAP4 connection to home server>
+
+      C: A001 SELECT REMOTE
+      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/REMOTE
+          IMAP://user;AUTH=*@SERVER3/REMOTE] Remote mailbox.
+          Try SERVER2 or SERVER3.
+
+      <Client opens second connection to remote server, and
+       issues the commands needed to process the items in the
+       remote mailbox>
+
+      S: * OK IMAP4rev1 server ready
+      C: B001 AUTHENTICATE KERBEROS_V4
+      <authentication exchange>
+      S: B001 OK user is authenticated
+
+      C: B002 SELECT REMOTE
+      S: * 12 EXISTS
+      S: * 1 RECENT
+      S: * OK [UNSEEN 10] Message 10 is first unseen
+      S: * OK [UIDVALIDITY 123456789]
+      S: * FLAGS (Answered Flagged Deleted Seen Draft)
+      S: * OK [PERMANENTFLAGS (Answered Deleted Seen ]
+      S: B002 OK [READ-WRITE] Selected completed
+
+      C: B003 FETCH 10:12 RFC822
+      S: * 10 FETCH . . .
+      S: * 11 FETCH . . .
+      S: * 12 FETCH . . .
+      S: B003 OK FETCH Completed
+
+
+
+
+Gahrns                      Standards Track                     [Page 4]
+
+RFC 2193                IMAP4 Mailbox Referrals           September 1997
+
+
+      <Client is finished processing the REMOTE mailbox and
+       wants to process a mailbox on its home server>
+
+      C: B004 LOGOUT
+      S: * BYE IMAP4rev1 server logging out
+      S: B004 OK LOGOUT Completed
+
+      <Client continues with first connection>
+
+      C: A002 SELECT INBOX
+      S: * 16 EXISTS
+      S: * 2 RECENT
+      S: * OK [UNSEEN 10] Message 10 is first unseen
+      S: * OK [UIDVALIDITY 123456789]
+      S: * FLAGS (Answered Flagged Deleted Seen Draft)
+      S: * OK [PERMANENTFLAGS (Answered Deleted Seen ]
+      S: A002 OK [READ-WRITE] Selected completed
+
+4.2. CREATE Referrals
+
+   An IMAP4 server MAY respond to the CREATE command with one or more
+   IMAP mailbox referrals, if it wishes to direct the client to issue
+   the CREATE against another server.  The server can employ any means,
+   such as examining the hierarchy of the specified mailbox name, in
+   determining which server the mailbox should be created on.
+
+   Example:
+
+      C: A001 CREATE "SHARED/FOO"
+      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/FOO]
+         Mailbox should be created on remote server
+
+   Alternatively, because a home server is required to maintain a
+   listing of referred remote mailboxes, a server MAY allow the creation
+   of a mailbox that will ultimately reside on a remote server against
+   the home server, and provide referrals on subsequent commands that
+   manipulate the mailbox.
+
+   Example:
+
+      C: A001 CREATE "SHARED/FOO"
+      S: A001 OK CREATE succeeded
+
+      C: A002 SELECT "SHARED/FOO"
+      S: A002 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/FOO]
+         Remote mailbox.  Try SERVER2
+
+
+
+
+
+Gahrns                      Standards Track                     [Page 5]
+
+RFC 2193                IMAP4 Mailbox Referrals           September 1997
+
+
+4.3. RENAME Referrals
+
+   An IMAP4 server MAY respond to the RENAME command with one or more
+   pairs of IMAP mailbox referrals.  In each pair of IMAP mailbox
+   referrals, the first one is an URL to the existing mailbox name and
+   the second is an URL to the requested new mailbox name.
+
+   If within an IMAP mailbox referral pair, the existing and new mailbox
+   URLs are on different servers, the remote servers are unable to
+   perform the RENAME operation.   To achieve the same behavior of
+   server RENAME, the client MAY issue the constituent CREATE, FETCH,
+   APPEND, and DELETE commands against both servers.
+
+   If within an IMAP mailbox referral pair, the existing and new mailbox
+   URLs are on the same server it is an indication that the currently
+   connected server is unable to perform the operation.  The client can
+   simply re-issue the RENAME command on the remote server.
+
+   Example:
+
+      C: A001 RENAME FOO BAR
+      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER1/FOO
+              IMAP://user;AUTH=*@SERVER2/BAR] Unable to rename mailbox
+              across servers
+
+   Since the existing and new mailbox names are on different servers,
+   the client would be required to make a connection to both servers and
+   issue the constituent commands require to achieve the RENAME.
+
+   Example:
+
+      C: A001 RENAME FOO BAR
+      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/FOO
+              IMAP://user;AUTH=*@SERVER2/BAR] Unable to rename mailbox
+              located on SERVER2
+
+   Since both the existing and new mailbox are on the same remote
+   server, the client can simply make a connection to the remote server
+   and re-issue the RENAME command.
+
+4.4. COPY Referrals
+
+   An IMAP4 server MAY respond to the COPY command with one or more IMAP
+   mailbox referrals.  This indicates that the destination mailbox is on
+   a remote server.  To achieve the same behavior of a server COPY, the
+   client MAY issue the constituent FETCH and APPEND commands against
+   both servers.
+
+
+
+
+Gahrns                      Standards Track                     [Page 6]
+
+RFC 2193                IMAP4 Mailbox Referrals           September 1997
+
+
+   Example:
+
+      C: A001 COPY 1 "SHARED/STUFF"
+      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/STUFF]
+              Unable to copy message(s) to SERVER2.
+
+5.1 RLIST command
+
+   Arguments:  reference name
+               mailbox name with possible wildcards
+
+   Responses:  untagged responses: LIST
+
+   Result:     OK - RLIST Completed
+               NO - RLIST Failure
+               BAD - command unknown or arguments invalid
+
+   The RLIST command behaves identically to its LIST counterpart, except
+   remote mailboxes are returned in addition to local mailboxes in the
+   LIST responses.
+
+5.2 RLSUB Command
+
+   Arguments:  reference name
+               mailbox name with possible wildcards
+
+   Responses:  untagged responses: LSUB
+
+   Result:     OK - RLSUB Completed
+               NO - RLSUB Failure
+               BAD - command unknown or arguments invalid
+
+   The RLSUB command behaves identically to its LSUB counterpart, except
+   remote mailboxes are returned in addition to local mailboxes in the
+   LSUB responses.
+
+6. Formal Syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (BNF) as described in [ABNF].
+
+   list_mailbox = <list_mailbox> as defined in [RFC-2060]
+
+   mailbox = <mailbox> as defined in [RFC-2060]
+
+   mailbox_referral = <tag> SPACE "NO" SPACE
+      <referral_response_code> (text / text_mime2)
+      ; See [RFC-2060] for <tag>, text and text_mime2 definition
+
+
+
+Gahrns                      Standards Track                     [Page 7]
+
+RFC 2193                IMAP4 Mailbox Referrals           September 1997
+
+
+   referral_response_code = "[" "REFERRAL" 1*(SPACE <url>) "]"
+      ; See [RFC-1738] for <url> definition
+
+   rlist = "RLIST" SPACE mailbox SPACE list_mailbox
+
+   rlsub = "RLSUB" SPACE mailbox SPACE list_mailbox
+
+6. Security Considerations
+
+   The IMAP4 referral mechanism makes use of IMAP URLs, and as such,
+   have the same security considerations as general internet URLs [RFC-
+   1738], and in particular IMAP URLs [RFC-2192].
+
+   With the MAILBOX-REFERRALS capability, it is potentially easier to
+   write a rogue server that injects a bogus referral response that
+   directs a user to an incorrect mailbox.  Although referrals reduce
+   the effort to write such a server, the referral response makes
+   detection of the intrusion easier.
+
+7. References
+
+   [RFC-2060], Crispin, M., "Internet Message Access Protocol - Version
+   4rev1", RFC 2060, University of Washington, December 1996.
+
+   [RFC-2192], Newman, C., "IMAP URL Scheme", RFC 2192, Innosoft,
+   September 1997.
+
+   [RFC-1738], Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
+   Resource Locators (URL)", RFC 1738, CERN, Xerox Corporation,
+   University of Minnesota, December 1994.
+
+   [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
+   Requirement Levels", RFC 2119, Harvard University, March 1997.
+
+   [ABNF], DRUMS working group, Dave Crocker Editor, "Augmented BNF for
+   Syntax Specifications: ABNF", Work in Progress, Internet Mail
+   Consortium, April 1997.
+
+8.  Acknowledgments
+
+   Many valuable suggestions were received from private discussions and
+   the IMAP4 mailing list.  In particular, Raymond Cheng, Mark Crispin,
+   Mark Keasling, Chris Newman and Larry Osterman made significant
+   contributions to this document.
+
+
+
+
+
+
+
+Gahrns                      Standards Track                     [Page 8]
+
+RFC 2193                IMAP4 Mailbox Referrals           September 1997
+
+
+9. Author's Address
+
+   Mike Gahrns
+   Microsoft
+   One Microsoft Way
+   Redmond, WA, 98072
+
+   Phone: (206) 936-9833
+   EMail: mikega@microsoft.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns                      Standards Track                     [Page 9]
+
diff --git a/imap/docs/rfc/rfc2195.txt b/imap/docs/rfc/rfc2195.txt
new file mode 100644
index 00000000..4a2725bf
--- /dev/null
+++ b/imap/docs/rfc/rfc2195.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group                                       J. Klensin
+Request for Comments: 2195                                    R. Catoe
+Category: Standards Track                                 P. Krumviede
+Obsoletes: 2095                                                    MCI
+                                                        September 1997
+
+
+       IMAP/POP AUTHorize Extension for Simple Challenge/Response
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   While IMAP4 supports a number of strong authentication mechanisms as
+   described in RFC 1731, it lacks any mechanism that neither passes
+   cleartext, reusable passwords across the network nor requires either
+   a significant security infrastructure or that the mail server update
+   a mail-system-wide user authentication file on each mail access.
+   This specification provides a simple challenge-response
+   authentication protocol that is suitable for use with IMAP4.  Since
+   it utilizes Keyed-MD5 digests and does not require that the secret be
+   stored in the clear on the server, it may also constitute an
+   improvement on APOP for POP3 use as specified in RFC 1734.
+
+1. Introduction
+
+   Existing Proposed Standards specify an AUTHENTICATE mechanism for the
+   IMAP4 protocol [IMAP, IMAP-AUTH] and a parallel AUTH mechanism for
+   the POP3 protocol [POP3-AUTH].  The AUTHENTICATE mechanism is
+   intended to be extensible; the four methods specified in [IMAP-AUTH]
+   are all fairly powerful and require some security infrastructure to
+   support.  The base POP3 specification [POP3] also contains a
+   lightweight challenge-response mechanism called APOP.  APOP is
+   associated with most of the risks associated with such protocols: in
+   particular, it requires that both the client and server machines have
+   access to the shared secret in cleartext form. CRAM offers a method
+   for avoiding such cleartext storage while retaining the algorithmic
+   simplicity of APOP in using only MD5, though in a "keyed" method.
+
+
+
+
+
+
+
+Klensin, Catoe & Krumviede  Standards Track                     [Page 1]
+
+RFC 2195              IMAP/POP AUTHorize Extension        September 1997
+
+
+   At present, IMAP [IMAP] lacks any facility corresponding to APOP.
+   The only alternative to the strong mechanisms identified in [IMAP-
+   AUTH] is a presumably cleartext username and password, supported
+   through the LOGIN command in [IMAP].  This document describes a
+   simple challenge-response mechanism, similar to APOP and PPP CHAP
+   [PPP], that can be used with IMAP (and, in principle, with POP3).
+
+   This mechanism also has the advantage over some possible alternatives
+   of not requiring that the server maintain information about email
+   "logins" on a per-login basis.  While mechanisms that do require such
+   per-login history records may offer enhanced security, protocols such
+   as IMAP, which may have several connections between a given client
+   and server open more or less simultaneous, may make their
+   implementation particularly challenging.
+
+2. Challenge-Response Authentication Mechanism (CRAM)
+
+   The authentication type associated with CRAM is "CRAM-MD5".
+
+   The data encoded in the first ready response contains an
+   presumptively arbitrary string of random digits, a timestamp, and the
+   fully-qualified primary host name of the server.  The syntax of the
+   unencoded form must correspond to that of an RFC 822 'msg-id'
+   [RFC822] as described in [POP3].
+
+   The client makes note of the data and then responds with a string
+   consisting of the user name, a space, and a 'digest'.  The latter is
+   computed by applying the keyed MD5 algorithm from [KEYED-MD5] where
+   the key is a shared secret and the digested text is the timestamp
+   (including angle-brackets).
+
+   This shared secret is a string known only to the client and server.
+   The `digest' parameter itself is a 16-octet value which is sent in
+   hexadecimal format, using lower-case ASCII characters.
+
+   When the server receives this client response, it verifies the digest
+   provided.  If the digest is correct, the server should consider the
+   client authenticated and respond appropriately.
+
+   Keyed MD5 is chosen for this application because of the greater
+   security imparted to authentication of short messages. In addition,
+   the use of the techniques described in [KEYED-MD5] for precomputation
+   of intermediate results make it possible to avoid explicit cleartext
+   storage of the shared secret on the server system by instead storing
+   the intermediate results which are known as "contexts".
+
+
+
+
+
+
+Klensin, Catoe & Krumviede  Standards Track                     [Page 2]
+
+RFC 2195              IMAP/POP AUTHorize Extension        September 1997
+
+
+   CRAM does not support a protection mechanism.
+
+   Example:
+
+   The examples in this document show the use of the CRAM mechanism with
+   the IMAP4 AUTHENTICATE command [IMAP-AUTH].  The base64 encoding of
+   the challenges and responses is part of the IMAP4 AUTHENTICATE
+   command, not part of the CRAM specification itself.
+
+     S: * OK IMAP4 Server
+     C: A0001 AUTHENTICATE CRAM-MD5
+     S: + PDE4OTYuNjk3MTcwOTUyQHBvc3RvZmZpY2UucmVzdG9uLm1jaS5uZXQ+
+     C: dGltIGI5MTNhNjAyYzdlZGE3YTQ5NWI0ZTZlNzMzNGQzODkw
+     S: A0001 OK CRAM authentication successful
+
+      In this example, the shared secret is the string
+      'tanstaaftanstaaf'.  Hence, the Keyed MD5 digest is produced by
+      calculating
+
+        MD5((tanstaaftanstaaf XOR opad),
+            MD5((tanstaaftanstaaf XOR ipad),
+            <1896.697170952@postoffice.reston.mci.net>))
+
+      where ipad and opad are as defined in the keyed-MD5 Work in
+      Progress [KEYED-MD5] and the string shown in the challenge is the
+      base64 encoding of <1896.697170952@postoffice.reston.mci.net>. The
+      shared secret is null-padded to a length of 64 bytes. If the
+      shared secret is longer than 64 bytes, the MD5 digest of the
+      shared secret is used as a 16 byte input to the keyed MD5
+      calculation.
+
+      This produces a digest value (in hexadecimal) of
+
+           b913a602c7eda7a495b4e6e7334d3890
+
+      The user name is then prepended to it, forming
+
+           tim b913a602c7eda7a495b4e6e7334d3890
+
+      Which is then base64 encoded to meet the requirements of the IMAP4
+      AUTHENTICATE command (or the similar POP3 AUTH command), yielding
+
+           dGltIGI5MTNhNjAyYzdlZGE3YTQ5NWI0ZTZlNzMzNGQzODkw
+
+
+
+
+
+
+
+
+Klensin, Catoe & Krumviede  Standards Track                     [Page 3]
+
+RFC 2195              IMAP/POP AUTHorize Extension        September 1997
+
+
+3. References
+
+   [CHAP]  Lloyd, B., and W. Simpson, "PPP Authentication Protocols",
+       RFC 1334, October 1992.
+
+   [IMAP] Crispin, M., "Internet Message Access Protocol - Version
+       4rev1", RFC 2060, University of Washington, December 1996.
+
+   [IMAP-AUTH] Myers, J., "IMAP4 Authentication Mechanisms",
+       RFC 1731, Carnegie Mellon, December 1994.
+
+   [KEYED-MD5] Krawczyk, Bellare, Canetti, "HMAC: Keyed-Hashing for
+       Message Authentication", RFC 2104, February 1997.
+
+   [MD5]  Rivest, R., "The MD5 Message Digest Algorithm",
+       RFC 1321, MIT Laboratory for Computer Science, April 1992.
+
+   [POP3] Myers, J., and M. Rose, "Post Office Protocol - Version 3",
+       STD 53, RFC 1939, Carnegie Mellon, May 1996.
+
+   [POP3-AUTH] Myers, J., "POP3 AUTHentication command", RFC 1734,
+       Carnegie Mellon, December, 1994.
+
+4. Security Considerations
+
+   It is conjectured that use of the CRAM authentication mechanism
+   provides origin identification and replay protection for a session.
+   Accordingly, a server that implements both a cleartext password
+   command and this authentication type should not allow both methods of
+   access for a given user.
+
+   While the saving, on the server, of "contexts" (see section 2) is
+   marginally better than saving the shared secrets in cleartext as is
+   required by CHAP [CHAP] and APOP [POP3], it is not sufficient to
+   protect the secrets if the server itself is compromised.
+   Consequently, servers that store the secrets or contexts must both be
+   protected to a level appropriate to the potential information value
+   in user mailboxes and identities.
+
+   As the length of the shared secret increases, so does the difficulty
+   of deriving it.
+
+   While there are now suggestions in the literature that the use of MD5
+   and keyed MD5 in authentication procedures probably has a limited
+   effective lifetime, the technique is now widely deployed and widely
+   understood.  It is believed that this general understanding may
+   assist with the rapid replacement, by CRAM-MD5, of the current uses
+   of permanent cleartext passwords in IMAP.   This document has been
+
+
+
+Klensin, Catoe & Krumviede  Standards Track                     [Page 4]
+
+RFC 2195              IMAP/POP AUTHorize Extension        September 1997
+
+
+   deliberately written to permit easy upgrading to use SHA (or whatever
+   alternatives emerge) when they are considered to be widely available
+   and adequately safe.
+
+   Even with the use of CRAM, users are still vulnerable to active
+   attacks.  An example of an increasingly common active attack is 'TCP
+   Session Hijacking' as described in CERT Advisory CA-95:01 [CERT95].
+
+   See section 1 above for additional discussion.
+
+5. Acknowledgements
+
+   This memo borrows ideas and some text liberally from [POP3] and
+   [RFC-1731] and thanks are due the authors of those documents.  Ran
+   Atkinson made a number of valuable technical and editorial
+   contributions to the document.
+
+6. Authors' Addresses
+
+   John C. Klensin
+   MCI Telecommunications
+   800 Boylston St, 7th floor
+   Boston, MA 02199
+   USA
+
+   EMail: klensin@mci.net
+   Phone: +1 617 960 1011
+
+   Randy Catoe
+   MCI Telecommunications
+   2100 Reston Parkway
+   Reston, VA 22091
+   USA
+
+   EMail: randy@mci.net
+   Phone: +1 703 715 7366
+
+   Paul Krumviede
+   MCI Telecommunications
+   2100 Reston Parkway
+   Reston, VA 22091
+   USA
+
+   EMail: paul@mci.net
+   Phone: +1 703 715 7251
+
+
+
+
+
+
+Klensin, Catoe & Krumviede  Standards Track                     [Page 5]
+
diff --git a/imap/docs/rfc/rfc2221.txt b/imap/docs/rfc/rfc2221.txt
new file mode 100644
index 00000000..81d00620
--- /dev/null
+++ b/imap/docs/rfc/rfc2221.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group                                           M. Gahrns
+Request for Comments: 2221                                      Microsoft
+Category: Standards Track                                    October 1997
+
+
+                         IMAP4 Login Referrals
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (1997).  All Rights Reserved.
+
+1. Abstract
+
+   When dealing with large amounts of users and many IMAP4 [RFC-2060]
+   servers, it is often necessary to move users from one IMAP4 server to
+   another.  For example, hardware failures or organizational changes
+   may dictate such a move.
+
+   Login referrals allow clients to transparently connect to an
+   alternate IMAP4 server, if their home IMAP4 server has changed.
+
+   A referral mechanism can provide efficiencies over the alternative
+   'proxy method', in which the local IMAP4 server contacts the remote
+   server on behalf of the client, and then transfers the data from the
+   remote server to itself, and then on to the client.  The referral
+   mechanism's direct client connection to the remote server is often a
+   more efficient use of bandwidth, and does not require the local
+   server to impersonate the client when authenticating to the remote
+   server.
+
+2. Conventions used in this document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.
+
+   A home server, is an IMAP4 server that contains the user's inbox.
+
+   A remote server is a server that contains remote mailboxes.
+
+
+
+
+
+Gahrns                      Standards Track                     [Page 1]
+
+RFC 2221                 IMAP4 Login Referrals              October 1997
+
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC-2119].
+
+3. Introduction and Overview
+
+   IMAP4 servers that support this extension MUST list the keyword
+   LOGIN-REFERRALS in their CAPABILITY response.  No client action is
+   needed to invoke the LOGIN-REFERRALS capability in a server.
+
+   A LOGIN-REFERRALS capable IMAP4 server SHOULD NOT return a referral
+   to a server that will return a referral. A client MUST NOT follow
+   more than 10 levels of referral without consulting the user.
+
+   A LOGIN-REFERRALS response code MUST contain as an argument a valid
+   IMAP server URL as defined in [IMAP-URL].
+
+   A home server referral consists of either a tagged NO or OK, or an
+   untagged BYE response that contains a LOGIN-REFERRALS response code.
+
+   Example: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/] Remote Server
+
+   NOTE: user;AUTH=* is specified as required by [IMAP-URL] to avoid a
+   client falling back to anonymous login.
+
+4. Home Server Referrals
+
+   A home server referral may be returned in response to an AUTHENTICATE
+   or LOGIN command, or it may appear in the connection startup banner.
+   If a server returns a home server referral in a tagged NO response,
+   that server does not contain any mailboxes that are accessible to the
+   user.  If a server returns a home server referral in a tagged OK
+   response, it indicates that the user's personal mailboxes are
+   elsewhere, but the server contains public mailboxes which are
+   readable by the user.  After receiving a home server referral, the
+   client can not make any assumptions as to whether this was a
+   permanent or temporary move of the user.
+
+4.1.  LOGIN and AUTHENTICATE Referrals
+
+   An IMAP4 server MAY respond to a LOGIN or AUTHENTICATE command with a
+   home server referral if it wishes to direct the user to another IMAP4
+   server.
+
+   Example:  C: A001 LOGIN MIKE PASSWORD
+             S: A001 NO [REFERRAL IMAP://MIKE@SERVER2/] Specified user
+                     is invalid on this server. Try SERVER2.
+
+
+
+
+Gahrns                      Standards Track                     [Page 2]
+
+RFC 2221                 IMAP4 Login Referrals              October 1997
+
+
+   Example:  C: A001 LOGIN MATTHEW PASSWORD
+             S: A001 OK [REFERRAL IMAP://MATTHEW@SERVER2/] Specified
+                     user's personal mailboxes located on Server2, but
+                     public mailboxes are available.
+
+   Example:  C: A001 AUTHENTICATE GSSAPI
+             <authentication exchange>
+             S: A001 NO [REFERRAL IMAP://user;AUTH=GSSAPI@SERVER2/]
+                     Specified user is invalid on this server. Try
+                     SERVER2.
+
+4.2. BYE at connection startup referral
+
+   An IMAP4 server MAY respond with an untagged BYE and a REFERRAL
+   response code that contains an IMAP URL to a home server if it is not
+   willing to accept connections and wishes to direct the client to
+   another IMAP4 server.
+
+   Example:  S: * BYE [REFERRAL IMAP://user;AUTH=*@SERVER2/] Server not
+                  accepting connections.  Try SERVER2
+
+5. Formal Syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (BNF) as described in [ABNF].
+
+   This amends the "resp_text_code" element of the IMAP4 grammar
+   described in [RFC-2060]
+
+   resp_text_code =/ "REFERRAL" SPACE <imapurl>
+      ; See [IMAP-URL] for definition of <imapurl>
+      ; See [RFC-2060] for base definition of resp_text_code
+
+6. Security Considerations
+
+   The IMAP4 login referral mechanism makes use of IMAP URLs, and as
+   such, have the same security considerations as general internet URLs
+   [RFC-1738], and in particular IMAP URLs [IMAP-URL].
+
+   A server MUST NOT give a login referral if authentication for that
+   user fails. This is to avoid revealing information about the user's
+   account to an unauthorized user.
+
+   With the LOGIN-REFERRALS capability, it is potentially easier to
+   write a rogue 'password catching' server that collects login data and
+   then refers the client to their actual IMAP4 server.  Although
+   referrals reduce the effort to write such a server, the referral
+   response makes detection of the intrusion easier.
+
+
+
+Gahrns                      Standards Track                     [Page 3]
+
+RFC 2221                 IMAP4 Login Referrals              October 1997
+
+
+7. References
+
+   [RFC-2060], Crispin, M., "Internet Message Access Protocol - Version
+   4rev1", RFC 2060, December 1996.
+
+   [IMAP-URL], Newman, C., "IMAP URL Scheme", RFC 2192, Innosoft,
+   September 1997.
+
+   [RFC-1738], Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
+   Resource Locators  (URL)", RFC 1738, December 1994.
+
+   [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
+   Requirement Levels", RFC 2119, March 1997.
+
+   [ABNF], DRUMS working group, Dave Crocker Editor, "Augmented BNF for
+   Syntax Specifications: ABNF", Work in Progress.
+
+8.  Acknowledgments
+
+   Many valuable suggestions were received from private discussions and
+   the IMAP4 mailing list.  In particular, Raymond Cheng, Mark Crispin,
+   Mark Keasling Chris Newman and Larry Osterman made significant
+   contributions to this document.
+
+9. Author's Address
+
+   Mike Gahrns
+   Microsoft
+   One Microsoft Way
+   Redmond, WA, 98072
+
+   Phone: (206) 936-9833
+   EMail: mikega@microsoft.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns                      Standards Track                     [Page 4]
+
+RFC 2221                 IMAP4 Login Referrals              October 1997
+
+
+10.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (1997).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implmentation may be prepared, copied, published
+   andand distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns                      Standards Track                     [Page 5]
+
diff --git a/imap/docs/rfc/rfc2342.txt b/imap/docs/rfc/rfc2342.txt
new file mode 100644
index 00000000..0926646d
--- /dev/null
+++ b/imap/docs/rfc/rfc2342.txt
@@ -0,0 +1,563 @@
+
+
+
+
+
+
+Network Working Group                                         M. Gahrns
+Request for Comments: 2342                                    Microsoft
+Category: Standards Track                                     C. Newman
+                                                               Innosoft
+                                                               May 1998
+
+
+                            IMAP4 Namespace
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (1998).  All Rights Reserved.
+
+1. Abstract
+
+   IMAP4 [RFC-2060] does not define a default server namespace. As a
+   result, two common namespace models have evolved:
+
+   The "Personal Mailbox" model, in which the default namespace that is
+   presented consists of only the user's personal mailboxes. To access
+   shared mailboxes, the user must use an escape mechanism to reach
+   another namespace.
+
+   The "Complete Hierarchy" model, in which the default namespace that
+   is presented includes the user's personal mailboxes along with any
+   other mailboxes they have access to.
+
+   These two models, create difficulties for certain client operations.
+   This document defines a NAMESPACE command that allows a client to
+   discover the prefixes of namespaces used by a server for personal
+   mailboxes, other users' mailboxes, and shared mailboxes.  This allows
+   a client to avoid much of the manual user configuration that is now
+   necessary when mixing and matching IMAP4 clients and servers.
+
+2. Conventions used in this document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.  If such lines are wrapped without a new "C:" or
+   "S:" label, then the wrapping is for editorial clarity and is not
+   part of the command.
+
+
+
+Gahrns & Newman             Standards Track                     [Page 1]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+   Personal Namespace: A namespace that the server considers within the
+   personal scope of the authenticated user on a particular connection.
+   Typically, only the authenticated user has access to mailboxes in
+   their Personal Namespace. It is the part of the namespace that
+   belongs to the user that is allocated for mailboxes. If an INBOX
+   exists for a user, it MUST appear within the user's personal
+   namespace.  In the typical case, there SHOULD be only one Personal
+   Namespace on a server.
+
+   Other Users' Namespace: A namespace that consists of mailboxes from
+   the Personal Namespaces of other users.  To access mailboxes in the
+   Other Users' Namespace, the currently authenticated user MUST be
+   explicitly granted access rights.  For example, it is common for a
+   manager to grant to their secretary access rights to their mailbox.
+   In the typical case, there SHOULD be only one Other Users' Namespace
+   on a server.
+
+   Shared Namespace: A namespace that consists of mailboxes that are
+   intended to be shared amongst users and do not exist within a user's
+   Personal Namespace.
+
+   The namespaces a server uses MAY differ on a per-user basis.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC-2119].
+
+3. Introduction and Overview
+
+   Clients often attempt to create mailboxes for such purposes as
+   maintaining a record of sent messages (e.g. "Sent Mail") or
+   temporarily saving messages being composed (e.g. "Drafts").  For
+   these clients to inter-operate correctly with the variety of IMAP4
+   servers available, the user must enter the prefix of the Personal
+   Namespace used by the server.  Using the NAMESPACE command, a client
+   is able to automatically discover this prefix without manual user
+   configuration.
+
+   In addition, users are often required to manually enter the prefixes
+   of various namespaces in order to view the mailboxes located there.
+   For example, they might be required to enter the prefix of #shared to
+   view the shared mailboxes namespace. The NAMESPACE command allows a
+   client to automatically discover the namespaces that are available on
+   a server. This allows a client to present the available namespaces to
+   the user in what ever manner it deems appropriate.  For example, a
+
+
+
+
+
+
+Gahrns & Newman             Standards Track                     [Page 2]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+   client could choose to initially display only personal mailboxes, or
+   it may choose to display the complete list of mailboxes available,
+   and initially position the user at the root of their Personal
+   Namespace.
+
+   A server MAY choose to make available to the NAMESPACE command only a
+   subset of the complete set of namespaces the server supports. To
+   provide the ability to access these namespaces, a client SHOULD allow
+   the user the ability to manually enter a namespace prefix.
+
+4. Requirements
+
+   IMAP4 servers that support this extension MUST list the keyword
+   NAMESPACE in their CAPABILITY response.
+
+   The NAMESPACE command is valid in the Authenticated and Selected
+   state.
+
+5. NAMESPACE Command
+
+   Arguments: none
+
+   Response:  an untagged NAMESPACE response that contains the prefix
+                 and hierarchy delimiter to the server's Personal
+                 Namespace(s), Other Users' Namespace(s), and Shared
+                 Namespace(s) that the server wishes to expose. The
+                 response will contain a NIL for any namespace class
+                 that is not available. Namespace_Response_Extensions
+                 MAY be included in the response.
+                 Namespace_Response_Extensions which are not on the IETF
+                 standards track, MUST be prefixed with an "X-".
+
+   Result:    OK - Command completed
+                 NO - Error: Can't complete command
+                 BAD - argument invalid
+
+   Example 5.1:
+   ===========
+
+      < A server that supports a single personal namespace.  No leading
+      prefix is used on personal mailboxes and "/" is the hierarchy
+      delimiter.>
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE (("" "/")) NIL NIL
+      S: A001 OK NAMESPACE command completed
+
+
+
+
+
+Gahrns & Newman             Standards Track                     [Page 3]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+   Example 5.2:
+   ===========
+
+      < A user logged on anonymously to a server.  No personal mailboxes
+      are associated with the anonymous user and the user does not have
+      access to the Other Users' Namespace.  No prefix is required to
+      access shared mailboxes and the hierarchy delimiter is "." >
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE NIL NIL (("" "."))
+      S: A001 OK NAMESPACE command completed
+
+   Example 5.3:
+   ===========
+
+      < A server that contains a Personal Namespace and a single Shared
+      Namespace. >
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE (("" "/")) NIL (("Public Folders/" "/"))
+      S: A001 OK NAMESPACE command completed
+
+   Example 5.4:
+   ===========
+
+      < A server that contains a Personal Namespace, Other Users'
+      Namespace and multiple Shared Namespaces.  Note that the hierarchy
+      delimiter used within each namespace can be different. >
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE (("" "/")) (("~" "/")) (("#shared/" "/")
+         ("#public/" "/")("#ftp/" "/")("#news." "."))
+      S: A001 OK NAMESPACE command completed
+
+   The prefix string allows a client to do things such as automatically
+   creating personal mailboxes or LISTing all available mailboxes within
+   a namespace.
+
+   Example 5.5:
+   ===========
+
+      < A server that supports only the Personal Namespace, with a
+      leading prefix of INBOX to personal mailboxes and a hierarchy
+      delimiter of ".">
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE (("INBOX." ".")) NIL  NIL
+      S: A001 OK NAMESPACE command completed
+
+
+
+Gahrns & Newman             Standards Track                     [Page 4]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+      < Automatically create a mailbox to store sent items.>
+
+      C: A002 CREATE "INBOX.Sent Mail"
+      S: A002 OK CREATE command completed
+
+   Although typically a server will support only a single Personal
+   Namespace, and a single Other User's Namespace, circumstances exist
+   where there MAY be multiples of these, and a client MUST be prepared
+   for them.   If a client is configured such that it is required to
+   create a certain mailbox, there can be circumstances where it is
+   unclear which Personal Namespaces it should create the mailbox in.
+   In these situations a client SHOULD let the user select which
+   namespaces to create the mailbox in.
+
+   Example 5.6:
+   ===========
+
+      < In this example, a server supports 2 Personal Namespaces.  In
+      addition to the regular Personal Namespace, the user has an
+      additional personal namespace to allow access to mailboxes in an
+      MH format mailstore. >
+
+      < The client is configured to save a copy of all mail sent by the
+      user into a mailbox called 'Sent Mail'.  Furthermore, after a
+      message is deleted from a mailbox, the client is configured to
+      move that message to a mailbox called 'Deleted Items'.>
+
+      < Note that this example demonstrates how some extension flags can
+      be passed to further describe the #mh namespace. >
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE (("" "/")("#mh/" "/" "X-PARAM" ("FLAG1" "FLAG2")))
+         NIL NIL
+      S: A001 OK NAMESPACE command completed
+
+      < It is desired to keep only one copy of sent mail. It is unclear
+      which Personal Namespace the client should use to create the 'Sent
+      Mail' mailbox.  The user is prompted to select a namespace and
+      only one 'Sent Mail' mailbox is created. >
+
+      C: A002 CREATE "Sent Mail"
+      S: A002 OK CREATE command completed
+
+      < The client is designed so that it keeps two 'Deleted Items'
+      mailboxes, one for each namespace. >
+
+      C: A003 CREATE "Delete Items"
+      S: A003 OK CREATE command completed
+
+
+
+Gahrns & Newman             Standards Track                     [Page 5]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+      C: A004 CREATE "#mh/Deleted Items"
+      S: A004 OK CREATE command completed
+
+   The next level of hierarchy following the Other Users' Namespace
+   prefix SHOULD consist of <username>, where <username> is a user name
+   as per the IMAP4 LOGIN or AUTHENTICATE command.
+
+   A client can construct a LIST command by appending a "%" to the Other
+   Users' Namespace prefix to discover the Personal Namespaces of other
+   users that are available to the currently authenticated user.
+
+   In response to such a LIST command, a server SHOULD NOT return user
+   names that have not granted access to their personal mailboxes to the
+   user in question.
+
+   A server MAY return a LIST response containing only the names of
+   users that have explicitly granted access to the user in question.
+
+   Alternatively, a server MAY return NO to such a LIST command,
+   requiring that a user name be included with the Other Users'
+   Namespace prefix before listing any other user's mailboxes.
+
+   Example 5.7:
+   ===========
+
+      < A server that supports providing a list of other user's
+      mailboxes that are accessible to the currently logged on user. >
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE (("" "/")) (("Other Users/" "/")) NIL
+      S: A001 OK NAMESPACE command completed
+
+      C: A002 LIST "" "Other Users/%"
+      S: * LIST () "/" "Other Users/Mike"
+      S: * LIST () "/" "Other Users/Karen"
+      S: * LIST () "/" "Other Users/Matthew"
+      S: * LIST () "/" "Other Users/Tesa"
+      S: A002 OK LIST command completed
+
+   Example 5.8:
+   ===========
+
+      < A server that does not support providing a list of other user's
+      mailboxes that are accessible to the currently logged on user.
+      The mailboxes are listable if the client includes the name of the
+      other user with the Other Users' Namespace prefix. >
+
+
+
+
+
+Gahrns & Newman             Standards Track                     [Page 6]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE (("" "/")) (("#Users/" "/")) NIL
+      S: A001 OK NAMESPACE command completed
+
+      < In this example, the currently logged on user has access to the
+      Personal Namespace of user Mike, but the server chose to suppress
+      this information in the LIST response.  However, by appending the
+      user name Mike (received through user input) to the Other Users'
+      Namespace prefix, the client is able to get a listing of the
+      personal mailboxes of user Mike. >
+
+      C: A002 LIST "" "#Users/%"
+      S: A002 NO The requested item could not be found.
+
+      C: A003 LIST "" "#Users/Mike/%"
+      S: * LIST () "/" "#Users/Mike/INBOX"
+      S: * LIST () "/" "#Users/Mike/Foo"
+      S: A003 OK LIST command completed.
+
+      A prefix string might not contain a hierarchy delimiter, because
+      in some cases it is not needed as part of the prefix.
+
+      Example 5.9:
+      ===========
+
+      < A server that allows access to the Other Users' Namespace by
+      prefixing the others' mailboxes with a '~' followed by <username>,
+      where <username> is a user name as per the IMAP4 LOGIN or
+      AUTHENTICATE command.>
+
+      C: A001 NAMESPACE
+      S: * NAMESPACE (("" "/")) (("~" "/")) NIL
+      S: A001 OK NAMESPACE command completed
+
+      < List the mailboxes for user mark >
+
+      C: A002 LIST "" "~mark/%"
+      S: * LIST () "/" "~mark/INBOX"
+      S: * LIST () "/" "~mark/foo"
+      S: A002 OK LIST command completed
+
+   Historical convention has been to start all namespaces with the "#"
+   character.  Namespaces that include the "#" character are not IMAP
+   URL [IMAP-URL] friendly requiring the "#" character to be represented
+   as %23 when within URLs.  As such, server implementers MAY instead
+   consider using namespace prefixes that do not contain the "#"
+   character.
+
+
+
+
+Gahrns & Newman             Standards Track                     [Page 7]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+6. Formal Syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (BNF) as described in [ABNF].
+
+   atom = <atom>
+      ; <atom> as defined in [RFC-2060]
+
+   Namespace = nil / "(" 1*( "(" string SP  (<"> QUOTED_CHAR <"> /
+      nil) *(Namespace_Response_Extension) ")" ) ")"
+
+   Namespace_Command = "NAMESPACE"
+
+   Namespace_Response_Extension = SP string SP "(" string *(SP string)
+      ")"
+
+   Namespace_Response = "*" SP "NAMESPACE" SP Namespace SP Namespace SP
+      Namespace
+
+      ; The first Namespace is the Personal Namespace(s)
+      ; The second Namespace is the Other Users' Namespace(s)
+      ; The third Namespace is the Shared Namespace(s)
+
+      nil = <nil>
+         ; <nil> as defined in [RFC-2060]
+
+      QUOTED_CHAR = <QUOTED_CHAR>
+         ; <QUOTED_CHAR> as defined in [RFC-2060]
+
+      string = <string>
+         ; <string> as defined in [RFC-2060]
+         ; Note that  the namespace prefix is to a mailbox and following
+         ; IMAP4 convention, any international string in the NAMESPACE
+         ; response MUST be of modified UTF-7 format as described in
+         ;  [RFC-2060].
+
+7. Security Considerations
+
+   In response to a LIST command containing an argument of the Other
+   Users' Namespace prefix, a server SHOULD NOT list users that have not
+   granted list access to their personal mailboxes to the currently
+   authenticated user.  Providing such a list, could compromise security
+   by potentially disclosing confidential information of who is located
+   on the server, or providing a starting point of a list of user
+   accounts to attack.
+
+
+
+
+
+
+Gahrns & Newman             Standards Track                     [Page 8]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+8. References
+
+   [RFC-2060], Crispin, M., "Internet Message Access Protocol Version
+   4rev1", RFC 2060, December 1996.
+
+   [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
+   Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [ABNF] Crocker, D., Editor, and P. Overell, "Augmented BNF for Syntax
+   Specifications: ABNF", RFC 2234, November 1997.
+
+   [IMAP-URL], Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+9.  Acknowledgments
+
+   Many people have participated in the discussion of IMAP namespaces on
+   the IMAP mailing list.  In particular, the authors would like to
+   thank Mark Crispin for many of the concepts relating to the Personal
+   Namespace and accessing the Personal Namespace of other users, Steve
+   Hole for summarizing the two namespace models, John Myers and Jack De
+   Winter for their work in a preceding effort trying to define a
+   standardized personal namespace, and Larry Osterman for his review
+   and collaboration on this document.
+
+11. Authors' Addresses
+
+   Mike Gahrns
+   Microsoft
+   One Microsoft Way
+   Redmond, WA, 98072, USA
+
+   Phone: (425) 936-9833
+   EMail: mikega@microsoft.com
+
+
+   Chris Newman
+   Innosoft International, Inc.
+   1050 East Garvey Ave. South
+   West Covina, CA, 91790, USA
+
+   EMail: chris.newman@innosoft.com
+
+
+
+
+
+
+
+
+
+
+Gahrns & Newman             Standards Track                     [Page 9]
+
+RFC 2342                    IMAP4 Namespace                     May 1998
+
+
+12.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (1998).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns & Newman             Standards Track                    [Page 10]
+
diff --git a/imap/docs/rfc/rfc2683.txt b/imap/docs/rfc/rfc2683.txt
new file mode 100644
index 00000000..d92e3405
--- /dev/null
+++ b/imap/docs/rfc/rfc2683.txt
@@ -0,0 +1,1291 @@
+
+
+
+
+
+
+Network Working Group                                           B. Leiba
+Request for Comments: 2683               IBM T.J. Watson Research Center
+Category: Informational                                   September 1999
+
+
+                  IMAP4 Implementation Recommendations
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  It does
+   not specify an Internet standard of any kind.  Distribution of this
+   memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (1999).  All Rights Reserved.
+
+1. Abstract
+
+   The IMAP4 specification [RFC-2060] describes a rich protocol for use
+   in building clients and servers for storage, retrieval, and
+   manipulation of electronic mail.  Because the protocol is so rich and
+   has so many implementation choices, there are often trade-offs that
+   must be made and issues that must be considered when designing such
+   clients and servers.  This document attempts to outline these issues
+   and to make recommendations in order to make the end products as
+   interoperable as possible.
+
+2. Conventions used in this document
+
+   In examples, "C:" indicates lines sent by a client that is connected
+   to a server.  "S:" indicates lines sent by the server to the client.
+
+   The words "must", "must not", "should", "should not", and "may" are
+   used with specific meaning in this document; since their meaning is
+   somewhat different from that specified in RFC 2119, we do not put
+   them in all caps here.  Their meaning is as follows:
+
+   must --       This word means that the action described is necessary
+                 to ensure interoperability.  The recommendation should
+                 not be ignored.
+   must not --   This phrase means that the action described will be
+                 almost certain to hurt interoperability.  The
+                 recommendation should not be ignored.
+
+
+
+
+
+
+
+Leiba                        Informational                      [Page 1]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   should --     This word means that the action described is strongly
+                 recommended and will enhance interoperability or
+                 usability.  The recommendation should not be ignored
+                 without careful consideration.
+   should not -- This phrase means that the action described is strongly
+                 recommended against, and might hurt interoperability or
+                 usability.  The recommendation should not be ignored
+                 without careful consideration.
+   may --        This word means that the action described is an
+                 acceptable implementation choice.  No specific
+                 recommendation is implied; this word is used to point
+                 out a choice that might not be obvious, or to let
+                 implementors know what choices have been made by
+                 existing implementations.
+
+3. Interoperability Issues and Recommendations
+
+3.1.   Accessibility
+
+   This section describes the issues related to access to servers and
+   server resources.  Concerns here include data sharing and maintenance
+   of client/server connections.
+
+3.1.1. Multiple Accesses of the Same Mailbox
+
+   One strong point of IMAP4 is that, unlike POP3, it allows for
+   multiple simultaneous access to a single mailbox.  A user can, thus,
+   read mail from a client at home while the client in the office is
+   still connected; or the help desk staff can all work out of the same
+   inbox, all seeing the same pool of questions.  An important point
+   about this capability, though is that NO SERVER IS GUARANTEED TO
+   SUPPORT THIS.  If you are selecting an IMAP server and this facility
+   is important to you, be sure that the server you choose to install,
+   in the configuration you choose to use, supports it.
+
+   If you are designing a client, you must not assume that you can
+   access the same mailbox more than once at a time.  That means
+
+   1. you must handle gracefully the failure of a SELECT command if the
+      server refuses the second SELECT,
+   2. you must handle reasonably the severing of your connection (see
+      "Severed Connections", below) if the server chooses to allow the
+      second SELECT by forcing the first off,
+   3. you must avoid making multiple connections to the same mailbox in
+      your own client (for load balancing or other such reasons), and
+   4. you must avoid using the STATUS command on a mailbox that you have
+      selected (with some server implementations the STATUS command has
+      the same problems with multiple access as do the SELECT and
+
+
+
+Leiba                        Informational                      [Page 2]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+      EXAMINE commands).
+
+   A further note about STATUS: The STATUS command is sometimes used to
+   check a non-selected mailbox for new mail.  This mechanism must not
+   be used to check for new mail in the selected mailbox; section 5.2 of
+   [RFC-2060] specifically forbids this in its last paragraph.  Further,
+   since STATUS takes a mailbox name it is an independent operation, not
+   operating on the selected mailbox.  Because of this, the information
+   it returns is not necessarily in synchronization with the selected
+   mailbox state.
+
+3.1.2. Severed Connections
+
+   The client/server connection may be severed for one of three reasons:
+   the client severs the connection, the server severs the connection,
+   or the connection is severed by outside forces beyond the control of
+   the client and the server (a telephone line drops, for example).
+   Clients and servers must both deal with these situations.
+
+   When the client wants to sever a connection, it's usually because it
+   has finished the work it needed to do on that connection.  The client
+   should send a LOGOUT command, wait for the tagged response, and then
+   close the socket.  But note that, while this is what's intended in
+   the protocol design, there isn't universal agreement here.  Some
+   contend that sending the LOGOUT and waiting for the two responses
+   (untagged BYE and tagged OK) is wasteful and unnecessary, and that
+   the client can simply close the socket.  The server should interpret
+   the closed socket as a log out by the client.  The counterargument is
+   that it's useful from the standpoint of cleanup, problem
+   determination, and the like, to have an explicit client log out,
+   because otherwise there is no way for the server to tell the
+   difference between "closed socket because of log out" and "closed
+   socket because communication was disrupted".  If there is a
+   client/server interaction problem, a client which routinely
+   terminates a session by breaking the connection without a LOGOUT will
+   make it much more difficult to determine the problem.
+
+   Because of this disagreement, server designers must be aware that
+   some clients might close the socket without sending a LOGOUT.  In any
+   case, whether or not a LOGOUT was sent, the server should not
+   implicitly expunge any messages from the selected mailbox.  If a
+   client wants the server to do so, it must send a CLOSE or EXPUNGE
+   command explicitly.
+
+   When the server wants to sever a connection it's usually due to an
+   inactivity timeout or is because a situation has arisen that has
+   changed the state of the mail store in a way that the server can not
+   communicate to the client.  The server should send an untagged BYE
+
+
+
+Leiba                        Informational                      [Page 3]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   response to the client and then close the socket.  Sending an
+   untagged BYE response before severing allows the server to send a
+   human-readable explanation of the problem to the client, which the
+   client may then log, display to the user, or both (see section 7.1.5
+   of [RFC-2060]).
+
+   Regarding inactivity timeouts, there is some controversy.  Unlike
+   POP, for which the design is for a client to connect, retrieve mail,
+   and log out, IMAP's design encourages long-lived (and mostly
+   inactive) client/server sessions.  As the number of users grows, this
+   can use up a lot of server resources, especially with clients that
+   are designed to maintain sessions for mailboxes that the user has
+   finished accessing.  To alleviate this, a server may implement an
+   inactivity timeout, unilaterally closing a session (after first
+   sending an untagged BYE, as noted above).  Some server operators have
+   reported dramatic improvements in server performance after doing
+   this.  As specified in [RFC-2060], if such a timeout is done it must
+   not be until at least 30 minutes of inactivity.  The reason for this
+   specification is to prevent clients from sending commands (such as
+   NOOP) to the server at frequent intervals simply to avert a too-early
+   timeout.  If the client knows that the server may not time out the
+   session for at least 30 minutes, then the client need not poll at
+   intervals more frequent than, say, 25 minutes.
+
+3.2.   Scaling
+
+   IMAP4 has many features that allow for scalability, as mail stores
+   become larger and more numerous.  Large numbers of users, mailboxes,
+   and messages, and very large messages require thought to handle
+   efficiently.  This document will not address the administrative
+   issues involved in large numbers of users, but we will look at the
+   other items.
+
+3.2.1. Flood Control
+
+   There are three situations when a client can make a request that will
+   result in a very large response - too large for the client reasonably
+   to deal with: there are a great many mailboxes available, there are a
+   great many messages in the selected mailbox, or there is a very large
+   message part.  The danger here is that the end user will be stuck
+   waiting while the server sends (and the client processes) an enormous
+   response.  In all of these cases there are things a client can do to
+   reduce that danger.
+
+   There is also the case where a client can flood a server, by sending
+   an arbitratily long command.  We'll discuss that issue, too, in this
+   section.
+
+
+
+
+Leiba                        Informational                      [Page 4]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+3.2.1.1.  Listing Mailboxes
+
+   Some servers present Usenet newsgroups to IMAP users.  Newsgroups,
+   and other such hierarchical mailbox structures, can be very numerous
+   but may have only a few entries at the top level of hierarchy.  Also,
+   some servers are built against mail stores that can, unbeknownst to
+   the server, have circular hierarchies - that is, it's possible for
+   "a/b/c/d" to resolve to the same file structure as "a", which would
+   then mean that "a/b/c/d/b" is the same as "a/b", and the hierarchy
+   will never end.  The LIST response in this case will be unlimited.
+
+   Clients that will have trouble with this are those that use
+
+       C: 001 LIST "" *
+
+   to determine the mailbox list.  Because of this, clients should not
+   use an unqualified "*" that way in the LIST command.  A safer
+   approach is to list each level of hierarchy individually, allowing
+   the user to traverse the tree one limb at a time, thus:
+
+       C: 001 LIST "" %
+       S: * LIST () "/" Banana
+       S: * LIST ...etc...
+       S: 001 OK done
+
+   and then
+
+       C: 002 LIST "" Banana/%
+       S: * LIST () "/" Banana/Apple
+       S: * LIST ...etc...
+       S: 002 OK done
+
+   Using this technique the client's user interface can give the user
+   full flexibility without choking on the voluminous reply to "LIST *".
+
+   Of course, it is still possible that the reply to
+
+       C: 005 LIST "" alt.fan.celebrity.%
+
+   may be thousands of entries long, and there is, unfortunately,
+   nothing the client can do to protect itself from that.  This has not
+   yet been a notable problem.
+
+   Servers that may export circular hierarchies (any server that
+   directly presents a UNIX file system, for instance) should limit the
+   hierarchy depth to prevent unlimited LIST responses.  A suggested
+   depth limit is 20 hierarchy levels.
+
+
+
+
+Leiba                        Informational                      [Page 5]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+3.2.1.2.  Fetching the List of Messages
+
+   When a client selects a mailbox, it is given a count, in the untagged
+   EXISTS response, of the messages in the mailbox.  This number can be
+   very large.  In such a case it might be unwise to use
+
+       C: 004 FETCH 1:* ALL
+
+   to populate the user's view of the mailbox.  One good method to avoid
+   problems with this is to batch the requests, thus:
+
+       C: 004 FETCH 1:50 ALL
+       S: * 1 FETCH ...etc...
+       S: 004 OK done
+       C: 005 FETCH 51:100 ALL
+       S: * 51 FETCH ...etc...
+       S: 005 OK done
+       C: 006 FETCH 101:150 ALL
+       ...etc...
+
+   Using this method, another command, such as "FETCH 6 BODY[1]" can be
+   inserted as necessary, and the client will not have its access to the
+   server blocked by a storm of FETCH replies.  (Such a method could be
+   reversed to fetch the LAST 50 messages first, then the 50 prior to
+   that, and so on.)
+
+   As a smart extension of this, a well designed client, prepared for
+   very large mailboxes, will not automatically fetch data for all
+   messages AT ALL.  Rather, the client will populate the user's view
+   only as the user sees it, possibly pre-fetching selected information,
+   and only fetching other information as the user scrolls to it.  For
+   example, to select only those messages beginning with the first
+   unseen one:
+
+       C: 003 SELECT INBOX
+       S: * 10000 EXISTS
+       S: * 80 RECENT
+       S: * FLAGS (\Answered \Flagged \Deleted \Draft \Seen)
+       S: * OK [UIDVALIDITY 824708485] UID validity status
+       S: * OK [UNSEEN 9921] First unseen message
+       S: 003 OK [READ-WRITE] SELECT completed
+       C: 004 FETCH 9921:* ALL
+       ... etc...
+
+   If the server does not return an OK [UNSEEN] response, the client may
+   use SEARCH UNSEEN to obtain that value.
+
+
+
+
+
+Leiba                        Informational                      [Page 6]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   This mechanism is good as a default presentation method, but only
+   works well if the default message order is acceptable.  A client may
+   want to present various sort orders to the user (by subject, by date
+   sent, by sender, and so on) and in that case (lacking a SORT
+   extension on the server side) the client WILL have to retrieve all
+   message descriptors.  A client that provides this service should not
+   do it by default and should inform the user of the costs of choosing
+   this option for large mailboxes.
+
+3.2.1.3.  Fetching a Large Body Part
+
+   The issue here is similar to the one for a list of messages.  In the
+   BODYSTRUCTURE response the client knows the size, in bytes, of the
+   body part it plans to fetch.  Suppose this is a 70 MB video clip. The
+   client can use partial fetches to retrieve the body part in pieces,
+   avoiding the problem of an uninterruptible 70 MB literal coming back
+   from the server:
+
+       C: 022 FETCH 3 BODY[1]<0.20000>
+       S: * 3 FETCH (FLAGS(\Seen) BODY[1]<0> {20000}
+       S: ...data...)
+       S: 022 OK done
+       C: 023 FETCH 3 BODY[1]<20001.20000>
+       S: * 3 FETCH (BODY[1]<20001> {20000}
+       S: ...data...)
+       S: 023 OK done
+       C: 024 FETCH 3 BODY[1]<40001.20000>
+       ...etc...
+
+3.2.1.4.  BODYSTRUCTURE vs. Entire Messages
+
+   Because FETCH BODYSTRUCTURE is necessary in order to determine the
+   number of body parts, and, thus, whether a message has "attachments",
+   clients often use FETCH FULL as their normal method of populating the
+   user's view of a mailbox.  The benefit is that the client can display
+   a paperclip icon or some such indication along with the normal
+   message summary.  However, this comes at a significant cost with some
+   server configurations.  The parsing needed to generate the FETCH
+   BODYSTRUCTURE response may be time-consuming compared with that
+   needed for FETCH ENVELOPE.  The client developer should consider this
+   issue when deciding whether the ability to add a paperclip icon is
+   worth the tradeoff in performance, especially with large mailboxes.
+
+   Some clients, rather than using FETCH BODYSTRUCTURE, use FETCH BODY[]
+   (or the equivalent FETCH RFC822) to retrieve the entire message.
+   They then do the MIME parsing in the client.  This may give the
+   client slightly more flexibility in some areas (access, for instance,
+   to header fields that aren't returned in the BODYSTRUCTURE and
+
+
+
+Leiba                        Informational                      [Page 7]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   ENVELOPE responses), but it can cause severe performance problems by
+   forcing the transfer of all body parts when the user might only want
+   to see some of them - a user logged on by modem and reading a small
+   text message with a large ZIP file attached may prefer to read the
+   text only and save the ZIP file for later.  Therefore, a client
+   should not normally retrieve entire messages and should retrieve
+   message body parts selectively.
+
+3.2.1.5.  Long Command Lines
+
+   A client can wind up building a very long command line in an effort to
+   try to be efficient about requesting information from a server.  This
+   can typically happen when a client builds a message set from selected
+   messages and doesn't recognise that contiguous blocks of messages may
+   be group in a range.  Suppose a user selects all 10,000 messages in a
+   large mailbox and then unselects message 287.  The client could build
+   that message set as "1:286,288:10000", but a client that doesn't
+   handle that might try to enumerate each message individually and build
+   "1,2,3,4, [and so on] ,9999,10000".  Adding that to the fetch command
+   results in a command line that's almost 49,000 octets long, and,
+   clearly, one can construct a command line that's even longer.
+
+   A client should limit the length of the command lines it generates to
+   approximately 1000 octets (including all quoted strings but not
+   including literals).  If the client is unable to group things into
+   ranges so that the command line is within that length, it should
+   split the request into multiple commands.  The client should use
+   literals instead of long quoted strings, in order to keep the command
+   length down.
+
+   For its part, a server should allow for a command line of at least
+   8000 octets.  This provides plenty of leeway for accepting reasonable
+   length commands from clients.  The server should send a BAD response
+   to a command that does not end within the server's maximum accepted
+   command length.
+
+3.2.2. Subscriptions
+
+   The client isn't the only entity that can get flooded: the end user,
+   too, may need some flood control.  The IMAP4 protocol provides such
+   control in the form of subscriptions.  Most servers support the
+   SUBSCRIBE, UNSUBSCRIBE, and LSUB commands, and many users choose to
+   narrow down a large list of available mailboxes by subscribing to the
+   ones that they usually want to see.  Clients, with this in mind,
+   should give the user a way to see only subscribed mailboxes.  A
+   client that never uses the LSUB command takes a significant usability
+   feature away from the user.  Of course, the client would not want to
+   hide the LIST command completely; the user needs to have a way to
+
+
+
+Leiba                        Informational                      [Page 8]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   choose between LIST and LSUB.  The usual way to do this is to provide
+   a setting like "show which mailboxes?:  [] all  [] subscribed only".
+
+3.2.3. Searching
+
+   IMAP SEARCH commands can become particularly troublesome (that is,
+   slow) on mailboxes containing a large number of messages.  So let's
+   put a few things in perspective in that regard.
+
+   The flag searches should be fast.  The flag searches (ALL, [UN]SEEN,
+   [UN]ANSWERED, [UN]DELETED, [UN]DRAFT, [UN]FLAGGED, NEW, OLD, RECENT)
+   are known to be used by clients for the client's own use (for
+   instance, some clients use "SEARCH UNSEEN" to find unseen mail and
+   "SEARCH DELETED" to warn the user before expunging messages).
+
+   Other searches, particularly the text searches (HEADER, TEXT, BODY)
+   are initiated by the user, rather than by the client itself, and
+   somewhat slower performance can be tolerated, since the user is aware
+   that the search is being done (and is probably aware that it might be
+   time-consuming).  A smart server might use dynamic indexing to speed
+   commonly used text searches.
+
+   The client may allow other commands to be sent to the server while a
+   SEARCH is in progress, but at the time of this writing there is
+   little or no server support for parallel processing of multiple
+   commands in the same session (and see "Multiple Accesses of the Same
+   Mailbox" above for a description of the dangers of trying to work
+   around this by doing your SEARCH in another session).
+
+   Another word about text searches: some servers, built on database
+   back-ends with indexed search capabilities, may return search results
+   that do not match the IMAP spec's "case-insensitive substring"
+   requirements.  While these servers are in violation of the protocol,
+   there is little harm in the violation as long as the search results
+   are used only in response to a user's request.  Still, developers of
+   such servers should be aware that they ARE violating the protocol,
+   should think carefully about that behaviour, and must be certain that
+   their servers respond accurately to the flag searches for the reasons
+   outlined above.
+
+   In addition, servers should support CHARSET UTF-8 [UTF-8] in
+   searches.
+
+
+
+
+
+
+
+
+
+Leiba                        Informational                      [Page 9]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+3.3    Avoiding Invalid Requests
+
+   IMAP4 provides ways for a server to tell a client in advance what is
+   and isn't permitted in some circumstances.  Clients should use these
+   features to avoid sending requests that a well designed client would
+   know to be invalid.  This section explains this in more detail.
+
+3.3.1. The CAPABILITY Command
+
+   All IMAP4 clients should use the CAPABILITY command to determine what
+   version of IMAP and what optional features a server supports.  The
+   client should not send IMAP4rev1 commands and arguments to a server
+   that does not advertize IMAP4rev1 in its CAPABILITY response.
+   Similarly, the client should not send IMAP4 commands that no longer
+   exist in IMAP4rev1 to a server that does not advertize IMAP4 in its
+   CAPABILITY response.  An IMAP4rev1 server is NOT required to support
+   obsolete IMAP4 or IMAP2bis commands (though some do; do not let this
+   fact lull you into thinking that it's valid to send such commands to
+   an IMAP4rev1 server).
+
+   A client should not send commands to probe for the existance of
+   certain extensions.  All standard and standards-track extensions
+   include CAPABILITY tokens indicating their presense.  All private and
+   experimental extensions should do the same, and clients that take
+   advantage of them should use the CAPABILITY response to determine
+   whether they may be used or not.
+
+3.3.2. Don't Do What the Server Says You Can't
+
+   In many cases, the server, in response to a command, will tell the
+   client something about what can and can't be done with a particular
+   mailbox.  The client should pay attention to this information and
+   should not try to do things that it's been told it can't do.
+
+   Examples:
+
+   *  Do not try to SELECT a mailbox that has the \Noselect flag set.
+   *  Do not try to CREATE a sub-mailbox in a mailbox that has the
+      \Noinferiors flag set.
+   *  Do not respond to a failing COPY or APPEND command by trying to
+      CREATE the target mailbox if the server does not respond with a
+      [TRYCREATE] response code.
+   *  Do not try to expunge a mailbox that has been selected with the
+      [READ-ONLY] response code.
+
+
+
+
+
+
+
+Leiba                        Informational                     [Page 10]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+3.4.   Miscellaneous Protocol Considerations
+
+   We describe here a number of important protocol-related issues, the
+   misunderstanding of which has caused significant interoperability
+   problems in IMAP4 implementations.  One general item is that every
+   implementer should be certain to take note of and to understand
+   section 2.2.2 and the preamble to section 7 of the IMAP4rev1 spec
+   [RFC-2060].
+
+3.4.1. Well Formed Protocol
+
+   We cannot stress enough the importance of adhering strictly to the
+   protocol grammar.  The specification of the protocol is quite rigid;
+   do not assume that you can insert blank space for "readability" if
+   none is called for.  Keep in mind that there are parsers out there
+   that will crash if there are protocol errors.  There are clients that
+   will report every parser burp to the user.  And in any case,
+   information that cannot be parsed is information that is lost.  Be
+   careful in your protocol generation.  And see "A Word About Testing",
+   below.
+
+   In particular, note that the string in the INTERNALDATE response is
+   NOT an RFC-822 date string - that is, it is not in the same format as
+   the first string in the ENVELOPE response.  Since most clients will,
+   in fact, accept an RFC-822 date string in the INTERNALDATE response,
+   it's easy to miss this in your interoperability testing.  But it will
+   cause a problem with some client, so be sure to generate the correct
+   string for this field.
+
+3.4.2. Special Characters
+
+   Certain characters, currently the double-quote and the backslash, may
+   not be sent as-is inside a quoted string.  These characters must be
+   preceded by the escape character if they are in a quoted string, or
+   else the string must be sent as a literal.  Both clients and servers
+   must handle this, both on output (they must send these characters
+   properly) and on input (they must be able to receive escaped
+   characters in quoted strings).  Example:
+
+       C: 001 LIST "" %
+       S: * LIST () "" INBOX
+       S: * LIST () "\\" TEST
+       S: * LIST () "\\" {12}
+       S: "My" mailbox
+       S: 001 OK done
+       C: 002 LIST "" "\"My\" mailbox\\%"
+       S: * LIST () "\\" {17}
+       S: "My" mailbox\Junk
+
+
+
+Leiba                        Informational                     [Page 11]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+       S: 002 OK done
+
+   Note that in the example the server sent the hierarchy delimiter as
+   an escaped character in the quoted string and sent the mailbox name
+   containing imbedded double-quotes as a literal.  The client used only
+   quoted strings, escaping both the backslash and the double-quote
+   characters.
+
+   The CR and LF characters may be sent ONLY in literals; they are not
+   allowed, even if escaped, inside quoted strings.
+
+   And while we're talking about special characters: the IMAP spec, in
+   the section titled "Mailbox International Naming Convention",
+   describes how to encode mailbox names in modified UTF-7 [UTF-7 and
+   RFC-2060].  Implementations must adhere to this in order to be
+   interoperable in the international market, and servers should
+   validate mailbox names sent by client and reject names that do not
+   conform.
+
+   As to special characters in userids and passwords: clients must not
+   restrict what a user may type in for a userid or a password.  The
+   formal grammar specifies that these are "astrings", and an astring
+   can be a literal.  A literal, in turn can contain any 8-bit
+   character, and clients must allow users to enter all 8-bit characters
+   here, and must pass them, unchanged, to the server (being careful to
+   send them as literals when necessary).  In particular, some server
+   configurations use "@" in user names, and some clients do not allow
+   that character to be entered; this creates a severe interoperability
+   problem.
+
+3.4.3. UIDs and UIDVALIDITY
+
+   Servers that support existing back-end mail stores often have no good
+   place to save UIDs for messages.  Often the existing mail store will
+   not have the concept of UIDs in the sense that IMAP has: strictly
+   increasing, never re-issued, 32-bit integers.  Some servers solve
+   this by storing the UIDs in a place that's accessible to end users,
+   allowing for the possibility that the users will delete them.  Others
+   solve it by re-assigning UIDs every time a mailbox is selected.
+
+   The server should maintain UIDs permanently for all messages if it
+   can.  If that's not possible, the server must change the UIDVALIDITY
+   value for the mailbox whenever any of the UIDs may have become
+   invalid.  Clients must recognize that the UIDVALIDITY has changed and
+   must respond to that condition by throwing away any information that
+   they have saved about UIDs in that mailbox.  There have been many
+   problems in this area when clients have failed to do this; in the
+   worst case it will result in loss of mail when a client deletes the
+
+
+
+Leiba                        Informational                     [Page 12]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   wrong piece of mail by using a stale UID.
+
+   It seems to be a common misunderstanding that "the UIDVALIDITY and
+   the UID, taken together, form a 64-bit identifier that uniquely
+   identifies a message on a server".  This is absolutely NOT TRUE.
+   There is no assurance that the UIDVALIDITY values of two mailboxes be
+   different, so the UIDVALIDITY in no way identifies a mailbox.  The
+   ONLY purpose of UIDVALIDITY is, as its name indicates, to give the
+   client a way to check the validity of the UIDs it has cached.  While
+   it is a valid implementation choice to put these values together to
+   make a 64-bit identifier for the message, the important concept here
+   is that UIDs are not unique between mailboxes; they are only unique
+   WITHIN a given mailbox.
+
+   Some server implementations have attempted to make UIDs unique across
+   the entire server.  This is inadvisable, in that it limits the life
+   of UIDs unnecessarily.  The UID is a 32-bit number and will run out
+   in reasonably finite time if it's global across the server.  If you
+   assign UIDs sequentially in one mailbox, you will not have to start
+   re-using them until you have had, at one time or another, 2**32
+   different messages in that mailbox.  In the global case, you will
+   have to reuse them once you have had, at one time or another, 2**32
+   different messages in the entire mail store.  Suppose your server has
+   around 8000 users registered (2**13).  That gives an average of 2**19
+   UIDs per user.  Suppose each user gets 32 messages (2**5) per day.
+   That gives you 2**14 days (16000+ days = about 45 years) before you
+   run out.  That may seem like enough, but multiply the usage just a
+   little (a lot of spam, a lot of mailing list subscriptions, more
+   users) and you limit yourself too much.
+
+   What's worse is that if you have to wrap the UIDs, and, thus, you
+   have to change UIDVALIDITY and invalidate the UIDs in the mailbox,
+   you have to do it for EVERY mailbox in the system, since they all
+   share the same UID pool.  If you assign UIDs per mailbox and you have
+   a problem, you only have to kill the UIDs for that one mailbox.
+
+   Under extreme circumstances (and this is extreme, indeed), the server
+   may have to invalidate UIDs while a mailbox is in use by a client -
+   that is, the UIDs that the client knows about in its active mailbox
+   are no longer valid.  In that case, the server must immediately
+   change the UIDVALIDITY and must communicate this to the client.  The
+   server may do this by sending an unsolicited UIDVALIDITY message, in
+   the same form as in response to the SELECT command.  Clients must be
+   prepared to handle such a message and the possibly coincident failure
+   of the command in process.  For example:
+
+
+
+
+
+
+Leiba                        Informational                     [Page 13]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+       C: 032 UID STORE 382 +Flags.silent \Deleted
+       S: * OK [UIDVALIDITY 12345] New UIDVALIDITY value!
+       S: 032 NO UID command rejected because UIDVALIDITY changed!
+       C: ...invalidates local information and re-fetches...
+       C: 033 FETCH 1:* UID
+       ...etc...
+
+   At the time of the writing of this document, the only server known to
+   do this does so only under the following condition: the client
+   selects INBOX, but there is not yet a physical INBOX file created.
+   Nonetheless, the SELECT succeeds, exporting an empty INBOX with a
+   temporary UIDVALIDITY of 1.  While the INBOX remains selected, mail
+   is delivered to the user, which creates the real INBOX file and
+   assigns a permanent UIDVALIDITY (that is likely not to be 1).  The
+   server reports the change of UIDVALIDITY, but as there were no
+   messages before, so no UIDs have actually changed, all the client
+   must do is accept the change in UIDVALIDITY.
+
+   Alternatively, a server may force the client to re-select the
+   mailbox, at which time it will obtain a new UIDVALIDITY value.  To do
+   this, the server closes this client session (see "Severed
+   Connections" above) and the client then reconnects and gets back in
+   synch.  Clients must be prepared for either of these behaviours.
+
+   We do not know of, nor do we anticipate the future existance of, a
+   server that changes UIDVALIDITY while there are existing messages,
+   but clients must be prepared to handle this eventuality.
+
+3.4.4. FETCH Responses
+
+   When a client asks for certain information in a FETCH command, the
+   server may return the requested information in any order, not
+   necessarily in the order that it was requested.  Further, the server
+   may return the information in separate FETCH responses and may also
+   return information that was not explicitly requested (to reflect to
+   the client changes in the state of the subject message).  Some
+   examples:
+
+       C: 001 FETCH 1 UID FLAGS INTERNALDATE
+       S: * 5 FETCH (FLAGS (\Deleted))
+       S: * 1 FETCH (FLAGS (\Seen) INTERNALDATE "..." UID 345)
+       S: 001 OK done
+
+   (In this case, the responses are in a different order.  Also, the
+   server returned a flag update for message 5, which wasn't part of the
+   client's request.)
+
+
+
+
+
+Leiba                        Informational                     [Page 14]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+       C: 002 FETCH 2 UID FLAGS INTERNALDATE
+       S: * 2 FETCH (INTERNALDATE "...")
+       S: * 2 FETCH (UID 399)
+       S: * 2 FETCH (FLAGS ())
+       S: 002 OK done
+
+   (In this case, the responses are in a different order and were
+   returned in separate responses.)
+
+       C: 003 FETCH 2 BODY[1]
+       S: * 2 FETCH (FLAGS (\Seen) BODY[1] {14}
+       S: Hello world!
+       S: )
+       S: 003 OK done
+
+   (In this case, the FLAGS response was added by the server, since
+   fetching the body part caused the server to set the \Seen flag.)
+
+   Because of this characteristic a client must be ready to receive any
+   FETCH response at any time and should use that information to update
+   its local information about the message to which the FETCH response
+   refers.  A client must not assume that any FETCH responses will come
+   in any particular order, or even that any will come at all.  If after
+   receiving the tagged response for a FETCH command the client finds
+   that it did not get all of the information requested, the client
+   should send a NOOP command to the server to ensure that the server
+   has an opportunity to send any pending EXPUNGE responses to the
+   client (see [RFC-2180]).
+
+3.4.5. RFC822.SIZE
+
+   Some back-end mail stores keep the mail in a canonical form, rather
+   than retaining the original MIME format of the messages.  This means
+   that the server must reassemble the message to produce a MIME stream
+   when a client does a fetch such as RFC822 or BODY[], requesting the
+   entire message.  It also may mean that the server has no convenient
+   way to know the RFC822.SIZE of the message.  Often, such a server
+   will actually have to build the MIME stream to compute the size, only
+   to throw the stream away and report the size to the client.
+
+   When this is the case, some servers have chosen to estimate the size,
+   rather than to compute it precisely.  Such an estimate allows the
+   client to display an approximate size to the user and to use the
+   estimate in flood control considerations (q.v.), but requires that
+   the client not use the size for things such as allocation of buffers,
+   because those buffers might then be too small to hold the actual MIME
+   stream.  Instead, a client should use the size that's returned in the
+   literal when you fetch the data.
+
+
+
+Leiba                        Informational                     [Page 15]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   The protocol requires that the RFC822.SIZE value returned by the
+   server be EXACT.  Estimating the size is a protocol violation, and
+   server designers must be aware that, despite the performance savings
+   they might realize in using an estimate, this practice will cause
+   some clients to fail in various ways.  If possible, the server should
+   compute the RFC822.SIZE for a particular message once, and then save
+   it for later retrieval.  If that's not possible, the server must
+   compute the value exactly every time.  Incorrect estimates do cause
+   severe interoperability problems with some clients.
+
+3.4.6. Expunged Messages
+
+   If the server allows multiple connections to the same mailbox, it is
+   often possible for messages to be expunged in one client unbeknownst
+   to another client.  Since the server is not allowed to tell the
+   client about these expunged messages in response to a FETCH command,
+   the server may have to deal with the issue of how to return
+   information about an expunged message.  There was extensive
+   discussion about this issue, and the results of that discussion are
+   summarized in [RFC-2180].  See that reference for a detailed
+   explanation and for recommendations.
+
+3.4.7. The Namespace Issue
+
+   Namespaces are a very muddy area in IMAP4 implementation right now
+   (see [NAMESPACE] for a proposal to clear the water a bit).  Until the
+   issue is resolved, the important thing for client developers to
+   understand is that some servers provide access through IMAP to more
+   than just the user's personal mailboxes, and, in fact, the user's
+   personal mailboxes may be "hidden" somewhere in the user's default
+   hierarchy.  The client, therefore, should provide a setting wherein
+   the user can specify a prefix to be used when accessing mailboxes. If
+   the user's mailboxes are all in "~/mail/", for instance, then the
+   user can put that string in the prefix.  The client would then put
+   the prefix in front of any name pattern in the LIST and LSUB
+   commands:
+
+       C: 001 LIST "" ~/mail/%
+
+   (See also "Reference Names in the LIST Command" below.)
+
+3.4.8. Creating Special-Use Mailboxes
+
+   It may seem at first that this is part of the namespace issue; it is
+   not, and is only indirectly related to it.  A number of clients like
+   to create special-use mailboxes with particular names.  Most
+   commonly, clients with a "trash folder" model of message deletion
+   want to create a mailbox with the name "Trash" or "Deleted".  Some
+
+
+
+Leiba                        Informational                     [Page 16]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   clients want to create a "Drafts" mailbox, an "Outbox" mailbox, or a
+   "Sent Mail" mailbox.  And so on.  There are two major
+   interoperability problems with this practice:
+
+   1. different clients may use different names for mailboxes with
+      similar functions (such as "Trash" and "Deleted"), or may manage
+      the same mailboxes in different ways, causing problems if a user
+      switches between clients and
+   2. there is no guarantee that the server will allow the creation of
+      the desired mailbox.
+
+   The client developer is, therefore, well advised to consider
+   carefully the creation of any special-use mailboxes on the server,
+   and, further, the client must not require such mailbox creation -
+   that is, if you do decide to do this, you must handle gracefully the
+   failure of the CREATE command and behave reasonably when your
+   special-use mailboxes do not exist and can not be created.
+
+   In addition, the client developer should provide a convenient way for
+   the user to select the names for any special-use mailboxes, allowing
+   the user to make these names the same in all clients used and to put
+   them where the user wants them.
+
+3.4.9. Reference Names in the LIST Command
+
+   Many implementers of both clients and servers are confused by the
+   "reference name" on the LIST command.  The reference name is intended
+   to be used in much the way a "cd" (change directory) command is used
+   on Unix, PC DOS, Windows, and OS/2 systems.  That is, the mailbox
+   name is interpreted in much the same way as a file of that name would
+   be found if one had done a "cd" command into the directory specified
+   by the reference name.  For example, in Unix we have the following:
+
+       > cd /u/jones/junk
+       > vi banana        [file is "/u/jones/junk/banana"]
+       > vi stuff/banana  [file is "/u/jones/junk/stuff/banana"]
+       > vi /etc/hosts    [file is "/etc/hosts"]
+
+   In the past, there have been several interoperability problems with
+   this.  First, while some IMAP servers are built on Unix or PC file
+   systems, many others are not, and the file system semantics do not
+   make sense in those configurations.  Second, while some IMAP servers
+   expose the underlying file system to the clients, others allow access
+   only to the user's personal mailboxes, or to some other limited set
+   of files, making such file-system-like semantics less meaningful.
+   Third, because the IMAP spec leaves the interpretation of the
+   reference name as "implementation-dependent", in the past the various
+   server implementations handled it in vastly differing ways.
+
+
+
+Leiba                        Informational                     [Page 17]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   The following recommendations are the result of significant
+   operational experience, and are intended to maximize
+   interoperability.
+
+   Server implementations must implement the reference argument in a way
+   that matches the intended "change directory" operation as closely as
+   possible.  As a minimum implementation, the reference argument may be
+   prepended to the mailbox name (while suppressing double delimiters;
+   see the next paragraph).  Even servers that do not provide a way to
+   break out of the current hierarchy (see "breakout facility" below)
+   must provide a reasonable implementation of the reference argument,
+   as described here, so that they will interoperate with clients that
+   use it.
+
+   Server implementations that prepend the reference argument to the
+   mailbox name should insert a hierarchy delimiter between them, and
+   must not insert a second if one is already present:
+
+       C: A001 LIST ABC DEF
+       S: * LIST () "/" ABC/DEF   <=== should do this
+       S: A001 OK done
+
+       C: A002 LIST ABC/ /DEF
+       S: * LIST () "/" ABC//DEF     <=== must not do this
+       S: A002 OK done
+
+   On clients, the reference argument is chiefly used to implement a
+   "breakout facility", wherein the user may directly access a mailbox
+   outside the "current directory" hierarchy.  Client implementations
+   should have an operational mode that does not use the reference
+   argument.  This is to interoperate with older servers that did not
+   implement the reference argument properly.  While it's a good idea to
+   give the user access to a breakout facility, clients that do not
+   intend to do so should not use the reference argument at all.
+
+   Client implementations should always place a trailing hierarchy
+   delimiter on the reference argument.  This is because some servers
+   prepend the reference argument to the mailbox name without inserting
+   a hierarchy delimiter, while others do insert a hierarchy delimiter
+   if one is not already present.  A client that puts the delimiter in
+   will work with both varieties of server.
+
+   Client implementations that implement a breakout facility should
+   allow the user to choose whether or not to use a leading hierarchy
+   delimiter on the mailbox argument.  This is because the handling of a
+   leading mailbox hierarchy delimiter also varies from server to
+   server, and even between different mailstores on the same server.  In
+   some cases, a leading hierarchy delimiter means "discard the
+
+
+
+Leiba                        Informational                     [Page 18]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   reference argument" (implementing the intended breakout facility),
+   thus:
+
+       C: A001 LIST ABC/ /DEF
+       S: * LIST () "/" /DEF
+       S: A001 OK done
+
+   In other cases, however, the two are catenated and the extra
+   hierarchy delimiter is discarded, thus:
+
+       C: A001 LIST ABC/ /DEF
+       S: * LIST () "/" ABC/DEF
+       S: A001 OK done
+
+   Client implementations must not assume that the server supports a
+   breakout facility, but may provide a way for the user to use one if
+   it is available.  Any breakout facility should be exported to the
+   user interface.  Note that there may be other "breakout" characters
+   besides the hierarchy delimiter (for instance, UNIX filesystem
+   servers are likely to use a leading "~" as well), and that their
+   interpretation is server-dependent.
+
+3.4.10.   Mailbox Hierarchy Delimiters
+
+   The server's selection of what to use as a mailbox hierarchy
+   delimiter is a difficult one, involving several issues: What
+   characters do users expect to see?  What characters can they enter
+   for a hierarchy delimiter if it is desired (or required) that the
+   user enter it?  What character can be used for the hierarchy
+   delimiter, noting that the chosen character can not otherwise be used
+   in the mailbox name?
+
+   Because some interfaces show users the hierarchy delimiters or allow
+   users to enter qualified mailbox names containing them, server
+   implementations should use delimiter characters that users generally
+   expect to see as name separators.  The most common characters used
+   for this are "/" (as in Unix file names), "\" (as in OS/2 and Windows
+   file names), and "." (as in news groups).  There is little to choose
+   among these apart from what users may expect or what is dictated by
+   the underlying file system, if any.  One consideration about using
+   "\" is that it's also a special character in the IMAP protocol. While
+   the use of other hierarchy delimiter characters is permissible, A
+   DESIGNER IS WELL ADVISED TO STAY WITH ONE FROM THIS SET unless the
+   server is intended for special purposes only.  Implementers might be
+   thinking about using characters such as "-", "_", ";", "&", "#", "@",
+   and "!", but they should be aware of the surprise to the user as well
+   as of the effect on URLs and other external specifications (since
+   some of these characters have special meanings there).  Also, a
+
+
+
+Leiba                        Informational                     [Page 19]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   server that uses "\" (and clients of such a server) must remember to
+   escape that character in quoted strings or to send literals instead.
+   Literals are recommended over escaped characters in quoted strings in
+   order to maintain compatibility with older IMAP versions that did not
+   allow escaped characters in quoted strings (but check the grammar to
+   see where literals are allowed):
+
+       C: 001 LIST "" {13}
+       S: + send literal
+       C: this\%\%\%\h*
+       S: * LIST () "\\" {27}
+       S: this\is\a\mailbox\hierarchy
+       S: 001 OK LIST complete
+
+   In any case, a server should not use normal alpha-numeric characters
+   (such as "X" or "0") as delimiters; a user would be very surprised to
+   find that "EXPENDITURES" actually represented a two-level hierarchy.
+   And a server should not use characters that are non-printable or
+   difficult or impossible to enter on a standard US keyboard.  Control
+   characters, box-drawing characters, and characters from non-US
+   alphabets fit into this category.  Their use presents
+   interoperability problems that are best avoided.
+
+   The UTF-7 encoding of mailbox names also raises questions about what
+   to do with the hierarchy delimiters in encoded names: do we encode
+   each hierarchy level and separate them with delimiters, or do we
+   encode the fully qualified name, delimiters and all?  The answer for
+   IMAP is the former: encode each hierarchy level separately, and
+   insert delimiters between.  This makes it particularly important not
+   to use as a hierarchy delimiter a character that might cause
+   confusion with IMAP's modified UTF-7 [UTF-7 and RFC-2060] encoding.
+
+   To repeat: a server should use "/", "\", or "." as its hierarchy
+   delimiter.  The use of any other character is likely to cause
+   problems and is STRONGLY DISCOURAGED.
+
+3.4.11.   ALERT Response Codes
+
+   The protocol spec is very clear on the matter of what to do with
+   ALERT response codes, and yet there are many clients that violate it
+   so it needs to be said anyway: "The human-readable text contains a
+   special alert that must be presented to the user in a fashion that
+   calls the user's attention to the message."  That should be clear
+   enough, but I'll repeat it here: Clients must present ALERT text
+   clearly to the user.
+
+
+
+
+
+
+Leiba                        Informational                     [Page 20]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+3.4.12.   Deleting Mailboxes
+
+   The protocol does not guarantee that a client may delete a mailbox
+   that is not empty, though on some servers it is permissible and is,
+   in fact, much faster than the alternative or deleting all the
+   messages from the client.  If the client chooses to try to take
+   advantage of this possibility it must be prepared to use the other
+   method in the even that the more convenient one fails.  Further, a
+   client should not try to delete the mailbox that it has selected, but
+   should first close that mailbox; some servers do not permit the
+   deletion of the selected mailbox.
+
+   That said, a server should permit the deletion of a non-empty
+   mailbox; there's little reason to pass this work on to the client.
+   Moreover, forbidding this prevents the deletion of a mailbox that for
+   some reason can not be opened or expunged, leading to possible
+   denial-of-service problems.
+
+   Example:
+
+       [User tells the client to delete mailbox BANANA, which is
+       currently selected...]
+       C: 008 CLOSE
+       S: 008 OK done
+       C: 009 DELETE BANANA
+       S: 009 NO Delete failed; mailbox is not empty.
+       C: 010 SELECT BANANA
+       S: * ... untagged SELECT responses
+       S: 010 OK done
+       C: 011 STORE 1:* +FLAGS.SILENT \DELETED
+       S: 011 OK done
+       C: 012 CLOSE
+       S: 012 OK done
+       C: 013 DELETE BANANA
+       S: 013 OK done
+
+3.5.   A Word About Testing
+
+   Since the whole point of IMAP is interoperability, and since
+   interoperability can not be tested in a vacuum, the final
+   recommendation of this treatise is, "Test against EVERYTHING."  Test
+   your client against every server you can get an account on.  Test
+   your server with every client you can get your hands on.  Many
+   clients make limited test versions available on the Web for the
+   downloading.  Many server owners will give serious client developers
+   guest accounts for testing.  Contact them and ask.  NEVER assume that
+   because your client works with one or two servers, or because your
+   server does fine with one or two clients, you will interoperate well
+
+
+
+Leiba                        Informational                     [Page 21]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+   in general.
+
+   In particular, in addition to everything else, be sure to test
+   against the reference implementations: the PINE client, the
+   University of Washington server, and the Cyrus server.
+
+   See the following URLs on the web for more information here:
+
+       IMAP Products and Sources: http://www.imap.org/products.html
+       IMC MailConnect: http://www.imc.org/imc-mailconnect
+
+4. Security Considerations
+
+   This document describes behaviour of clients and servers that use the
+   IMAP4 protocol, and as such, has the same security considerations as
+   described in [RFC-2060].
+
+5. References
+
+   [RFC-2060]  Crispin, M., "Internet Message Access Protocol - Version
+               4rev1", RFC 2060, December 1996.
+
+   [RFC-2119]  Bradner, S., "Key words for use in RFCs to Indicate
+               Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC-2180]  Gahrns, M., "IMAP4 Multi-Accessed Mailbox Practice", RFC
+               2180, July 1997.
+
+   [UTF-8]     Yergeau, F., " UTF-8, a transformation format of Unicode
+               and ISO 10646", RFC 2044, October 1996.
+
+   [UTF-7]     Goldsmith, D. and M. Davis, "UTF-7, a Mail-Safe
+               Transformation Format of Unicode", RFC 2152, May 1997.
+
+   [NAMESPACE] Gahrns, M. and C. Newman, "IMAP4 Namespace", Work in
+               Progress.
+
+6. Author's Address
+
+   Barry Leiba
+   IBM T.J. Watson Research Center
+   30 Saw Mill River Road
+   Hawthorne, NY  10532
+
+   Phone: 1-914-784-7941
+   EMail: leiba@watson.ibm.com
+
+
+
+
+
+Leiba                        Informational                     [Page 22]
+
+RFC 2683          IMAP4 Implementation Recommendations    September 1999
+
+
+7. Full Copyright Statement
+
+   Copyright (C) The Internet Society (1999).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Leiba                        Informational                     [Page 23]
+
diff --git a/imap/docs/rfc/rfc2971.txt b/imap/docs/rfc/rfc2971.txt
new file mode 100644
index 00000000..9e7264dc
--- /dev/null
+++ b/imap/docs/rfc/rfc2971.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group                                        T. Showalter
+Request for Comments: 2971                                Mirapoint, Inc.
+Category: Standards Track                                    October 2000
+
+
+                           IMAP4 ID extension
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2000).  All Rights Reserved.
+
+Abstract
+
+   The ID extension to the Internet Message Access Protocol - Version
+   4rev1 (IMAP4rev1) protocol allows the server and client to exchange
+   identification information on their implementation in order to make
+   bug reports and usage statistics more complete.
+
+1. Introduction
+
+   The IMAP4rev1 protocol described in [IMAP4rev1] provides a method for
+   accessing remote mail stores, but it provides no facility to
+   advertise what program a client or server uses to provide service.
+   This makes it difficult for implementors to get complete bug reports
+   from users, as it is frequently difficult to know what client or
+   server is in use.
+
+   Additionally, some sites may wish to assemble usage statistics based
+   on what clients are used, but in an an environment where users are
+   permitted to obtain and maintain their own clients this is difficult
+   to accomplish.
+
+   The ID command provides a facility to advertise information on what
+   programs are being used along with contact information (should bugs
+   ever occur).
+
+
+
+
+
+
+
+
+Showalter                   Standards Track                     [Page 1]
+
+RFC 2971                   IMAP4 ID extension               October 2000
+
+
+2. Conventions Used in this Document
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [KEYWORDS].
+
+   The conventions used in this document are the same as specified in
+   [IMAP4rev1].  In examples, "C:" and "S:" indicate lines sent by the
+   client and server respectively.  Line breaks have been inserted for
+   readability.
+
+3. Specification
+
+   The sole purpose of the ID extension is to enable clients and servers
+   to exchange information on their implementations for the purposes of
+   statistical analysis and problem determination.
+
+   This information is be submitted to a server by any client wishing to
+   provide information for statistical purposes, provided the server
+   advertises its willingness to take the information with the atom "ID"
+   included in the list of capabilities returned by the CAPABILITY
+   command.
+
+   Implementations MUST NOT make operational changes based on the data
+   sent as part of the ID command or response.  The ID command is for
+   human consumption only, and is not to be used in improving the
+   performance of clients or servers.
+
+   This includes, but is not limited to, the following:
+
+      Servers MUST NOT attempt to work around client bugs by using
+      information from the ID command.  Clients MUST NOT attempt to work
+      around server bugs based on the ID response.
+
+      Servers MUST NOT provide features to a client or otherwise
+      optimize for a particular client by using information from the ID
+      command.  Clients MUST NOT provide features to a server or
+      otherwise optimize for a particular server based on the ID
+      response.
+
+      Servers MUST NOT deny access to or refuse service for a client
+      based on information from the ID command.  Clients MUST NOT refuse
+      to operate or limit their operation with a server based on the ID
+      response.
+
+
+
+
+
+
+
+Showalter                   Standards Track                     [Page 2]
+
+RFC 2971                   IMAP4 ID extension               October 2000
+
+
+   Rationale: It is imperative that this extension not supplant IMAP's
+   CAPABILITY mechanism with a ad-hoc approach where implementations
+   guess each other's features based on who they claim to be.
+
+   Implementations MUST NOT send false information in an ID command.
+
+   Implementations MAY send less information than they have available or
+   no information at all.  Such behavior may be useful to preserve user
+   privacy.  See Security Considerations, section 7.
+
+3.1. ID Command
+
+   Arguments:  client parameter list or NIL
+
+   Responses:  OPTIONAL untagged response: ID
+
+   Result:     OK    identification information accepted
+               BAD   command unknown or arguments invalid
+
+   Implementation identification information is sent by the client with
+   the ID command.
+
+   This command is valid in any state.
+
+   The information sent is in the form of a list of field/value pairs.
+   Fields are permitted to be any IMAP4 string, and values are permitted
+   to be any IMAP4 string or NIL.  A value of NIL indicates that the
+   client can not or will not specify this information.  The client may
+   also send NIL instead of the list, indicating that it wants to send
+   no information, but would still accept a server response.
+
+   The available fields are defined in section 3.3.
+
+   Example:  C: a023 ID ("name" "sodr" "version" "19.34" "vendor"
+                 "Pink Floyd Music Limited")
+             S: * ID NIL
+             S: a023 OK ID completed
+
+3.2. ID Response
+
+   Contents:   server parameter list
+
+   In response to an ID command issued by the client, the server replies
+   with a tagged response containing information on its implementation.
+   The format is the same as the client list.
+
+
+
+
+
+
+Showalter                   Standards Track                     [Page 3]
+
+RFC 2971                   IMAP4 ID extension               October 2000
+
+
+   Example:  C: a042 ID NIL
+             S: * ID ("name" "Cyrus" "version" "1.5" "os" "sunos"
+                  "os-version" "5.5" "support-url"
+                  "mailto:cyrus-bugs+@andrew.cmu.edu")
+             S: a042 OK ID command completed
+
+   A server MUST send a tagged ID response to an ID command.  However, a
+   server MAY send NIL in place of the list.
+
+3.3. Defined Field Values
+
+   Any string may be sent as a field, but the following are defined to
+   describe certain values that might be sent.  Implementations are free
+   to send none, any, or all of these.  Strings are not case-sensitive.
+   Field strings MUST NOT be longer than 30 octets.  Value strings MUST
+   NOT be longer than 1024 octets.  Implementations MUST NOT send more
+   than 30 field-value pairs.
+
+     name            Name of the program
+     version         Version number of the program
+     os              Name of the operating system
+     os-version      Version of the operating system
+     vendor          Vendor of the client/server
+     support-url     URL to contact for support
+     address         Postal address of contact/vendor
+     date            Date program was released, specified as a date-time
+                       in IMAP4rev1
+     command         Command used to start the program
+     arguments       Arguments supplied on the command line, if any
+                       if any
+     environment     Description of environment, i.e., UNIX environment
+                       variables or Windows registry settings
+
+   Implementations MUST NOT use contact information to submit automatic
+   bug reports.  Implementations may include information from an ID
+   response in a report automatically prepared, but are prohibited from
+   sending the report without user authorization.
+
+   It is preferable to find the name and version of the underlying
+   operating system at runtime in cases where this is possible.
+
+   Information sent via an ID response may violate user privacy.  See
+   Security Considerations, section 7.
+
+   Implementations MUST NOT send the same field name more than once.
+
+
+
+
+
+
+Showalter                   Standards Track                     [Page 4]
+
+RFC 2971                   IMAP4 ID extension               October 2000
+
+
+4. Formal Syntax
+
+   This  syntax is intended to augment the grammar specified in
+   [IMAP4rev1] in order to provide for the ID command.  This
+   specification uses the augmented Backus-Naur Form (BNF) notation as
+   used in [IMAP4rev1].
+
+     command_any ::= "CAPABILITY" / "LOGOUT" / "NOOP" / x_command / id
+         ;; adds id command to command_any in [IMAP4rev1]
+
+     id ::= "ID" SPACE id_params_list
+
+     id_response ::= "ID" SPACE id_params_list
+
+     id_params_list ::= "(" #(string SPACE nstring) ")" / nil
+         ;; list of field value pairs
+
+     response_data ::= "*" SPACE (resp_cond_state / resp_cond_bye /
+         mailbox_data / message_data / capability_data / id_response)
+
+5. Use of the ID extension with Firewalls and Other Intermediaries
+
+   There exist proxies, firewalls, and other intermediary systems that
+   can intercept an IMAP session and make changes to the data exchanged
+   in the session.  Such intermediaries are not anticipated by the IMAP4
+   protocol design and are not within the scope of the IMAP4 standard.
+   However, in order for the ID command to be useful in the presence of
+   such intermediaries, those intermediaries need to take special note
+   of the ID command and response.  In particular, if an intermediary
+   changes any part of the IMAP session it must also change the ID
+   command to advertise its presence.
+
+   A firewall MAY act to block transmission of specific information
+   fields in the ID command and response that it believes reveal
+   information that could expose a security vulnerability.  However, a
+   firewall SHOULD NOT disable the extension, when present, entirely,
+   and SHOULD NOT unconditionally remove either the client or server
+   list.
+
+   Finally, it should be noted that a firewall, when handling a
+   CAPABILITY response, MUST NOT allow the names of extensions to be
+   returned to the client that the firewall has no knowledge of.
+
+
+
+
+
+
+
+
+
+Showalter                   Standards Track                     [Page 5]
+
+RFC 2971                   IMAP4 ID extension               October 2000
+
+
+6. References
+
+   [KEYWORDS]  Bradner, S., "Key words for use in RFCs to Indicate
+               Requirement Levels", RFC 2119, March 1997.
+
+   [IMAP4rev1] Crispin, M., "Internet Message Access Protocol - Version
+               4rev1", RFC 2060, October 1996.
+
+   [RFC-822]   Crocker, D., "Standard for the Format of ARPA Internet
+               Text Messages", STD 11, RFC 822, August 1982.
+
+7. Security Considerations
+
+   This extension has the danger of violating the privacy of users if
+   misused.  Clients and servers should notify users that they implement
+   and enable the ID command.
+
+   It is highly desirable that implementations provide a method of
+   disabling ID support, perhaps by not sending ID at all, or by sending
+   NIL as the argument to the ID command or response.
+
+   Implementors must exercise extreme care in adding fields sent as part
+   of an ID command or response.  Some fields, including a processor ID
+   number, Ethernet address, or other unique (or mostly unique)
+   identifier allow tracking of users in ways that violate user privacy
+   expectations.
+
+   Having implementation information of a given client or server may
+   make it easier for an attacker to gain unauthorized access due to
+   security holes.
+
+   Since this command includes arbitrary data and does not require the
+   user to authenticate, server implementations are cautioned to guard
+   against an attacker sending arbitrary garbage data in order to fill
+   up the ID log.  In particular, if a server naively logs each ID
+   command to disk without inspecting it, an attacker can simply fire up
+   thousands of connections and send a few kilobytes of random data.
+   Servers have to guard against this.  Methods include truncating
+   abnormally large responses; collating responses by storing only a
+   single copy, then keeping a counter of the number of times that
+   response has been seen; keeping only particularly interesting parts
+   of responses; and only logging responses of users who actually log
+   in.
+
+   Security is affected by firewalls which modify the IMAP protocol
+   stream; see section 5, Use of the ID Extension with Firewalls and
+   Other Intermediaries, for more information.
+
+
+
+
+Showalter                   Standards Track                     [Page 6]
+
+RFC 2971                   IMAP4 ID extension               October 2000
+
+
+8. Author's Address
+
+   Tim Showalter
+   Mirapoint, Inc.
+   909 Hermosa Ct.
+   Sunnyvale, CA 94095
+
+   EMail: tjs@mirapoint.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Showalter                   Standards Track                     [Page 7]
+
+RFC 2971                   IMAP4 ID extension               October 2000
+
+
+9.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (2000).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Showalter                   Standards Track                     [Page 8]
+
diff --git a/imap/docs/rfc/rfc3348.txt b/imap/docs/rfc/rfc3348.txt
new file mode 100644
index 00000000..500871cc
--- /dev/null
+++ b/imap/docs/rfc/rfc3348.txt
@@ -0,0 +1,339 @@
+
+
+
+
+
+
+Network Working Group                                          M. Gahrns
+Request for Comments: 3348                                      R. Cheng
+Category: Informational                                        Microsoft
+                                                               July 2002
+
+
+             The Internet Message Action Protocol (IMAP4)
+                        Child Mailbox Extension
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  It does
+   not specify an Internet standard of any kind.  Distribution of this
+   memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2002).  All Rights Reserved.
+
+Abstract
+
+   The Internet Message Action Protocol (IMAP4) CHILDREN extension
+   provides a mechanism for a client to efficiently determine if a
+   particular mailbox has children, without issuing a LIST "" * or a
+   LIST "" % for each mailbox.
+
+1. Conventions used in this document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.  If such lines are wrapped without a new "C:" or
+   "S:" label, then the wrapping is for editorial clarity and is not
+   part of the command.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC-2119].
+
+2. Introduction and Overview
+
+   Many IMAP4 [RFC-2060] clients present to the user a hierarchical view
+   of the mailboxes that a user has access to.  Rather than initially
+   presenting to the user the entire mailbox hierarchy, it is often
+   preferable to show to the user a collapsed outline list of the
+   mailbox hierarchy (particularly if there is a large number of
+   mailboxes).  The user can then expand the collapsed outline hierarchy
+   as needed.  It is common to include within the collapsed hierarchy a
+
+
+
+
+
+Gahrns, et al.               Informational                      [Page 1]
+
+RFC 3348             IMAP4 Child Mailbox Extension             July 2002
+
+
+   visual clue (such as a "+") to indicate that there are child
+   mailboxes under a particular mailbox.  When the visual clue is
+   clicked the hierarchy list is expanded to show the child mailboxes.
+
+   Several IMAP vendors implemented this proposal, and it is proposed to
+   document this behavior and functionality as an Informational RFC.
+
+   There is interest in addressing the general extensibility of the IMAP
+   LIST command through an IMAP LIST Extension draft.  Similar
+   functionality to the \HasChildren and \HasNoChildren flags could be
+   incorporated into this new LIST Extension.  It is proposed that the
+   more general LIST Extension draft proceed on the standards track with
+   this proposal being relegated to informational status only.
+
+   If the functionality of the \HasChildren and \HasNoChildren flags
+   were incorporated into a more general LIST extension, this would have
+   the advantage that a client could then have the opportunity to
+   request whether or not the server should return this information.
+   This would be an advantage over the current draft for servers where
+   this information is expensive to compute, since the server would only
+   need to compute the information when it knew that the client
+   requesting the information was able to consume it.
+
+3. Requirements
+
+   IMAP4 servers that support this extension MUST list the keyword
+   CHILDREN in their CAPABILITY response.
+
+   The CHILDREN extension defines two new attributes that MAY be
+   returned within a LIST response.
+
+   \HasChildren - The presence of this attribute indicates that the
+   mailbox has child mailboxes.
+
+   Servers SHOULD NOT return \HasChildren if child mailboxes exist, but
+   none will be displayed to the current user in a LIST response (as
+   should be the case where child mailboxes exist, but a client does not
+   have permissions to access them.)  In this case, \HasNoChildren
+   SHOULD be used.
+
+   In many cases, however, a server may not be able to efficiently
+   compute whether a user has access to all child mailboxes, or multiple
+   users may be accessing the same account and simultaneously changing
+   the mailbox hierarchy.  As such a client MUST be prepared to accept
+   the \HasChildren attribute as a hint.  That is, a mailbox MAY be
+   flagged with the \HasChildren attribute, but no child mailboxes will
+   appear in a subsequent LIST response.
+
+
+
+
+Gahrns, et al.               Informational                      [Page 2]
+
+RFC 3348             IMAP4 Child Mailbox Extension             July 2002
+
+
+   Example 3.1:
+   ============
+
+   /*** Consider a server that has the following mailbox hierarchy:
+
+   INBOX
+   ITEM_1
+      ITEM_1A
+   ITEM_2
+      TOP_SECRET
+
+   Where INBOX, ITEM_1 and ITEM_2 are top level mailboxes.  ITEM_1A is a
+   child mailbox of ITEM_1 and TOP_SECRET is a child mailbox of ITEM_2
+   that the currently logged on user does NOT have access to.
+
+   Note that in this case, the server is not able to efficiently compute
+   access rights to child mailboxes and responds with a \HasChildren
+   attribute for mailbox ITEM_2, even though ITEM_2/TOP_SECRET does not
+   appear in the list response.  ***/
+
+   C: A001 LIST "" *
+   S: * LIST (\HasNoChildren) "/" INBOX
+   S: * LIST (\HasChildren) "/" ITEM_1
+   S: * LIST (\HasNoChildren) "/" ITEM_1/ITEM_1A
+   S: * LIST (\HasChildren) "/" ITEM_2
+   S: A001 OK LIST Completed
+
+   \HasNoChildren - The presence of this attribute indicates that the
+   mailbox has NO child mailboxes that are accessible to the currently
+   authenticated user.  If a mailbox has the \Noinferiors attribute, the
+   \HasNoChildren attribute is redundant and SHOULD be omitted in the
+   LIST response.
+
+   In some instances a server that supports the CHILDREN extension MAY
+   NOT be able to determine whether a mailbox has children.  For example
+   it may have difficulty determining whether there are child mailboxes
+   when LISTing mailboxes while operating in a particular namespace.
+
+   In these cases, a server MAY exclude both the \HasChildren and
+   \HasNoChildren attributes in the LIST response.  As such, a client
+   can not make any assumptions about whether a mailbox has children
+   based upon the absence of a single attribute.
+
+   It is an error for the server to return both a \HasChildren and a
+   \HasNoChildren attribute in a LIST response.
+
+
+
+
+
+
+Gahrns, et al.               Informational                      [Page 3]
+
+RFC 3348             IMAP4 Child Mailbox Extension             July 2002
+
+
+   It is an error for the server to return both a \HasChildren and a
+   \NoInferiors attribute in a LIST response.
+
+   Note: the \HasNoChildren attribute should not be confused with the
+   IMAP4 [RFC-2060] defined attribute \Noinferiors which indicates that
+   no child mailboxes exist now and none can be created in the future.
+
+   The \HasChildren and \HasNoChildren attributes might not be returned
+   in response to a LSUB response.  Many servers maintain a simple
+   mailbox subscription list that is not updated when the underlying
+   mailbox structure is changed.  A client MUST NOT assume that
+   hierarchy information will be maintained in the subscription list.
+
+   RLIST is a command defined in [RFC-2193] that includes in a LIST
+   response mailboxes that are accessible only via referral.  That is, a
+   client must explicitly issue an RLIST command to see a list of these
+   mailboxes.  Thus in the case where a mailbox has child mailboxes that
+   are available only via referral, the mailboxes would appear as
+   \HasNoChildren in response to the LIST command, and \HasChildren in
+   response to the RLIST command.
+
+5. Formal Syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (BNF) as described in [ABNF].
+
+   Two new mailbox attributes are defined as flag_extensions to the
+   IMAP4 mailbox_list response:
+
+   HasChildren = "\HasChildren"
+
+   HasNoChildren = "\HasNoChildren"
+
+6. Security Considerations
+
+   This extension provides a client a more efficient means of
+   determining whether a particular mailbox has children.  If a mailbox
+   has children, but the currently authenticated user does not have
+   access to any of them, the server SHOULD respond with a
+   \HasNoChildren attribute.  In many cases, however, a server may not
+   be able to efficiently compute whether a user has access to all child
+   mailboxes.  If such a server responds with a \HasChildren attribute,
+   when in fact the currently authenticated user does not have access to
+   any child mailboxes, potentially more information is conveyed about
+   the mailbox than intended.  A server designed with such levels of
+   security in mind SHOULD NOT attach the \HasChildren attribute to a
+   mailbox unless the server is certain that the user has access to at
+   least one of the child mailboxes.
+
+
+
+Gahrns, et al.               Informational                      [Page 4]
+
+RFC 3348             IMAP4 Child Mailbox Extension             July 2002
+
+
+7. References
+
+   [RFC-2060] Crispin, M., "Internet Message Access Protocol - Version
+              4rev1", RFC 2060, December 1996.
+
+   [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC-2234] Crocker, D. and P. Overell, Editors, "Augmented BNF for
+              Syntax Specifications: ABNF", RFC 2234, November 1997.
+
+   [RFC-2193] Gahrns, M., "IMAP4 Mailbox Referrals", RFC 2193, September
+              1997.
+
+8.  Acknowledgments
+
+   The authors would like to thank the participants of several IMC Mail
+   Connect events for their input when this idea was originally
+   presented and refined.
+
+9. Author's Address
+
+   Mike Gahrns
+   Microsoft
+   One Microsoft Way
+   Redmond, WA, 98052
+   Phone: (425) 936-9833
+   EMail: mikega@microsoft.com
+
+   Raymond Cheng
+   Microsoft
+   One Microsoft Way
+   Redmond, WA, 98052
+   Phone: (425) 703-4913
+   EMail: raych@microsoft.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns, et al.               Informational                      [Page 5]
+
+RFC 3348             IMAP4 Child Mailbox Extension             July 2002
+
+
+10. Full Copyright Statement
+
+   Copyright (C) The Internet Society (2002).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns, et al.               Informational                      [Page 6]
+
diff --git a/imap/docs/rfc/rfc3501.txt b/imap/docs/rfc/rfc3501.txt
new file mode 100644
index 00000000..6f470dd1
--- /dev/null
+++ b/imap/docs/rfc/rfc3501.txt
@@ -0,0 +1,6052 @@
+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 3501                      University of Washington
+Obsoletes: 2060                                               March 2003
+Category: Standards Track
+
+
+            INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+Abstract
+
+   The Internet Message Access Protocol, Version 4rev1 (IMAP4rev1)
+   allows a client to access and manipulate electronic mail messages on
+   a server.  IMAP4rev1 permits manipulation of mailboxes (remote
+   message folders) in a way that is functionally equivalent to local
+   folders.  IMAP4rev1 also provides the capability for an offline
+   client to resynchronize with the server.
+
+   IMAP4rev1 includes operations for creating, deleting, and renaming
+   mailboxes, checking for new messages, permanently removing messages,
+   setting and clearing flags, RFC 2822 and RFC 2045 parsing, searching,
+   and selective fetching of message attributes, texts, and portions
+   thereof.  Messages in IMAP4rev1 are accessed by the use of numbers.
+   These numbers are either message sequence numbers or unique
+   identifiers.
+
+   IMAP4rev1 supports a single server.  A mechanism for accessing
+   configuration information to support multiple IMAP4rev1 servers is
+   discussed in RFC 2244.
+
+   IMAP4rev1 does not specify a means of posting mail; this function is
+   handled by a mail transfer protocol such as RFC 2821.
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 1]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+Table of Contents
+
+   IMAP4rev1 Protocol Specification ................................  4
+   1.      How to Read This Document ...............................  4
+   1.1.    Organization of This Document ...........................  4
+   1.2.    Conventions Used in This Document .......................  4
+   1.3.    Special Notes to Implementors ...........................  5
+   2.      Protocol Overview .......................................  6
+   2.1.    Link Level ..............................................  6
+   2.2.    Commands and Responses ..................................  6
+   2.2.1.  Client Protocol Sender and Server Protocol Receiver .....  6
+   2.2.2.  Server Protocol Sender and Client Protocol Receiver .....  7
+   2.3.    Message Attributes ......................................  8
+   2.3.1.  Message Numbers .........................................  8
+   2.3.1.1.        Unique Identifier (UID) Message Attribute .......  8
+   2.3.1.2.        Message Sequence Number Message Attribute ....... 10
+   2.3.2.  Flags Message Attribute ................................. 11
+   2.3.3.  Internal Date Message Attribute ......................... 12
+   2.3.4.  [RFC-2822] Size Message Attribute ....................... 12
+   2.3.5.  Envelope Structure Message Attribute .................... 12
+   2.3.6.  Body Structure Message Attribute ........................ 12
+   2.4.    Message Texts ........................................... 13
+   3.      State and Flow Diagram .................................. 13
+   3.1.    Not Authenticated State ................................. 13
+   3.2.    Authenticated State ..................................... 13
+   3.3.    Selected State .......................................... 13
+   3.4.    Logout State ............................................ 14
+   4.      Data Formats ............................................ 16
+   4.1.    Atom .................................................... 16
+   4.2.    Number .................................................. 16
+   4.3.    String .................................................. 16
+   4.3.1.  8-bit and Binary Strings ................................ 17
+   4.4.    Parenthesized List ...................................... 17
+   4.5.    NIL ..................................................... 17
+   5.      Operational Considerations .............................. 18
+   5.1.    Mailbox Naming .......................................... 18
+   5.1.1.  Mailbox Hierarchy Naming ................................ 19
+   5.1.2.  Mailbox Namespace Naming Convention ..................... 19
+   5.1.3.  Mailbox International Naming Convention ................. 19
+   5.2.    Mailbox Size and Message Status Updates ................. 21
+   5.3.    Response when no Command in Progress .................... 21
+   5.4.    Autologout Timer ........................................ 22
+   5.5.    Multiple Commands in Progress ........................... 22
+   6.      Client Commands ........................................  23
+   6.1.    Client Commands - Any State ............................  24
+   6.1.1.  CAPABILITY Command .....................................  24
+   6.1.2.  NOOP Command ...........................................  25
+   6.1.3.  LOGOUT Command .........................................  26
+
+
+
+Crispin                     Standards Track                     [Page 2]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   6.2.    Client Commands - Not Authenticated State ..............  26
+   6.2.1.  STARTTLS Command .......................................  27
+   6.2.2.  AUTHENTICATE Command ...................................  28
+   6.2.3.  LOGIN Command ..........................................  30
+   6.3.    Client Commands - Authenticated State ..................  31
+   6.3.1.  SELECT Command .........................................  32
+   6.3.2.  EXAMINE Command ........................................  34
+   6.3.3.  CREATE Command .........................................  34
+   6.3.4.  DELETE Command .........................................  35
+   6.3.5.  RENAME Command .........................................  37
+   6.3.6.  SUBSCRIBE Command ......................................  39
+   6.3.7.  UNSUBSCRIBE Command ....................................  39
+   6.3.8.  LIST Command ...........................................  40
+   6.3.9.  LSUB Command ...........................................  43
+   6.3.10. STATUS Command .........................................  44
+   6.3.11. APPEND Command .........................................  46
+   6.4.    Client Commands - Selected State .......................  47
+   6.4.1.  CHECK Command ..........................................  47
+   6.4.2.  CLOSE Command ..........................................  48
+   6.4.3.  EXPUNGE Command ........................................  49
+   6.4.4.  SEARCH Command .........................................  49
+   6.4.5.  FETCH Command ..........................................  54
+   6.4.6.  STORE Command ..........................................  58
+   6.4.7.  COPY Command ...........................................  59
+   6.4.8.  UID Command ............................................  60
+   6.5.    Client Commands - Experimental/Expansion ...............  62
+   6.5.1.  X<atom> Command ........................................  62
+   7.      Server Responses .......................................  62
+   7.1.    Server Responses - Status Responses ....................  63
+   7.1.1.  OK Response ............................................  65
+   7.1.2.  NO Response ............................................  66
+   7.1.3.  BAD Response ...........................................  66
+   7.1.4.  PREAUTH Response .......................................  67
+   7.1.5.  BYE Response ...........................................  67
+   7.2.    Server Responses - Server and Mailbox Status ...........  68
+   7.2.1.  CAPABILITY Response ....................................  68
+   7.2.2.  LIST Response ..........................................  69
+   7.2.3.  LSUB Response ..........................................  70
+   7.2.4   STATUS Response ........................................  70
+   7.2.5.  SEARCH Response ........................................  71
+   7.2.6.  FLAGS Response .........................................  71
+   7.3.    Server Responses - Mailbox Size ........................  71
+   7.3.1.  EXISTS Response ........................................  71
+   7.3.2.  RECENT Response ........................................  72
+   7.4.    Server Responses - Message Status ......................  72
+   7.4.1.  EXPUNGE Response .......................................  72
+   7.4.2.  FETCH Response .........................................  73
+   7.5.    Server Responses - Command Continuation Request ........  79
+
+
+
+Crispin                     Standards Track                     [Page 3]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   8.      Sample IMAP4rev1 connection ............................  80
+   9.      Formal Syntax ..........................................  81
+   10.     Author's Note ..........................................  92
+   11.     Security Considerations ................................  92
+   11.1.   STARTTLS Security Considerations .......................  92
+   11.2.   Other Security Considerations ..........................  93
+   12.     IANA Considerations ....................................  94
+   Appendices .....................................................  95
+   A.      References .............................................  95
+   B.      Changes from RFC 2060 ..................................  97
+   C.      Key Word Index ......................................... 103
+   Author's Address ............................................... 107
+   Full Copyright Statement ....................................... 108
+
+IMAP4rev1 Protocol Specification
+
+1.      How to Read This Document
+
+1.1.    Organization of This Document
+
+   This document is written from the point of view of the implementor of
+   an IMAP4rev1 client or server.  Beyond the protocol overview in
+   section 2, it is not optimized for someone trying to understand the
+   operation of the protocol.  The material in sections 3 through 5
+   provides the general context and definitions with which IMAP4rev1
+   operates.
+
+   Sections 6, 7, and 9 describe the IMAP commands, responses, and
+   syntax, respectively.  The relationships among these are such that it
+   is almost impossible to understand any of them separately.  In
+   particular, do not attempt to deduce command syntax from the command
+   section alone; instead refer to the Formal Syntax section.
+
+1.2.    Conventions Used in This Document
+
+   "Conventions" are basic principles or procedures.  Document
+   conventions are noted in this section.
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
+   be interpreted as described in [KEYWORDS].
+
+   The word "can" (not "may") is used to refer to a possible
+   circumstance or situation, as opposed to an optional facility of the
+   protocol.
+
+
+
+Crispin                     Standards Track                     [Page 4]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   "User" is used to refer to a human user, whereas "client" refers to
+   the software being run by the user.
+
+   "Connection" refers to the entire sequence of client/server
+   interaction from the initial establishment of the network connection
+   until its termination.
+
+   "Session" refers to the sequence of client/server interaction from
+   the time that a mailbox is selected (SELECT or EXAMINE command) until
+   the time that selection ends (SELECT or EXAMINE of another mailbox,
+   CLOSE command, or connection termination).
+
+   Characters are 7-bit US-ASCII unless otherwise specified.  Other
+   character sets are indicated using a "CHARSET", as described in
+   [MIME-IMT] and defined in [CHARSET].  CHARSETs have important
+   additional semantics in addition to defining character set; refer to
+   these documents for more detail.
+
+   There are several protocol conventions in IMAP.  These refer to
+   aspects of the specification which are not strictly part of the IMAP
+   protocol, but reflect generally-accepted practice.  Implementations
+   need to be aware of these conventions, and avoid conflicts whether or
+   not they implement the convention.  For example, "&" may not be used
+   as a hierarchy delimiter since it conflicts with the Mailbox
+   International Naming Convention, and other uses of "&" in mailbox
+   names are impacted as well.
+
+1.3.    Special Notes to Implementors
+
+   Implementors of the IMAP protocol are strongly encouraged to read the
+   IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in
+   conjunction with this document, to help understand the intricacies of
+   this protocol and how best to build an interoperable product.
+
+   IMAP4rev1 is designed to be upwards compatible from the [IMAP2] and
+   unpublished IMAP2bis protocols.  IMAP4rev1 is largely compatible with
+   the IMAP4 protocol described in RFC 1730; the exception being in
+   certain facilities added in RFC 1730 that proved problematic and were
+   subsequently removed.  In the course of the evolution of IMAP4rev1,
+   some aspects in the earlier protocols have become obsolete.  Obsolete
+   commands, responses, and data formats which an IMAP4rev1
+   implementation can encounter when used with an earlier implementation
+   are described in [IMAP-OBSOLETE].
+
+   Other compatibility issues with IMAP2bis, the most common variant of
+   the earlier protocol, are discussed in [IMAP-COMPAT].  A full
+   discussion of compatibility issues with rare (and presumed extinct)
+
+
+
+
+Crispin                     Standards Track                     [Page 5]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is
+   primarily of historical interest.
+
+   IMAP was originally developed for the older [RFC-822] standard, and
+   as a consequence several fetch items in IMAP incorporate "RFC822" in
+   their name.  With the exception of RFC822.SIZE, there are more modern
+   replacements; for example, the modern version of RFC822.HEADER is
+   BODY.PEEK[HEADER].  In all cases, "RFC822" should be interpreted as a
+   reference to the updated [RFC-2822] standard.
+
+2.      Protocol Overview
+
+2.1.    Link Level
+
+   The IMAP4rev1 protocol assumes a reliable data stream such as that
+   provided by TCP.  When TCP is used, an IMAP4rev1 server listens on
+   port 143.
+
+2.2.    Commands and Responses
+
+   An IMAP4rev1 connection consists of the establishment of a
+   client/server network connection, an initial greeting from the
+   server, and client/server interactions.  These client/server
+   interactions consist of a client command, server data, and a server
+   completion result response.
+
+   All interactions transmitted by client and server are in the form of
+   lines, that is, strings that end with a CRLF.  The protocol receiver
+   of an IMAP4rev1 client or server is either reading a line, or is
+   reading a sequence of octets with a known count followed by a line.
+
+2.2.1.  Client Protocol Sender and Server Protocol Receiver
+
+   The client command begins an operation.  Each client command is
+   prefixed with an identifier (typically a short alphanumeric string,
+   e.g., A0001, A0002, etc.) called a "tag".  A different tag is
+   generated by the client for each command.
+
+   Clients MUST follow the syntax outlined in this specification
+   strictly.  It is a syntax error to send a command with missing or
+   extraneous spaces or arguments.
+
+   There are two cases in which a line from the client does not
+   represent a complete command.  In one case, a command argument is
+   quoted with an octet count (see the description of literal in String
+   under Data Formats); in the other case, the command arguments require
+   server feedback (see the AUTHENTICATE command).  In either case, the
+
+
+
+
+Crispin                     Standards Track                     [Page 6]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   server sends a command continuation request response if it is ready
+   for the octets (if appropriate) and the remainder of the command.
+   This response is prefixed with the token "+".
+
+        Note: If instead, the server detected an error in the
+        command, it sends a BAD completion response with a tag
+        matching the command (as described below) to reject the
+        command and prevent the client from sending any more of the
+        command.
+
+        It is also possible for the server to send a completion
+        response for some other command (if multiple commands are
+        in progress), or untagged data.  In either case, the
+        command continuation request is still pending; the client
+        takes the appropriate action for the response, and reads
+        another response from the server.  In all cases, the client
+        MUST send a complete command (including receiving all
+        command continuation request responses and command
+        continuations for the command) before initiating a new
+        command.
+
+   The protocol receiver of an IMAP4rev1 server reads a command line
+   from the client, parses the command and its arguments, and transmits
+   server data and a server command completion result response.
+
+2.2.2.  Server Protocol Sender and Client Protocol Receiver
+
+   Data transmitted by the server to the client and status responses
+   that do not indicate command completion are prefixed with the token
+   "*", and are called untagged responses.
+
+   Server data MAY be sent as a result of a client command, or MAY be
+   sent unilaterally by the server.  There is no syntactic difference
+   between server data that resulted from a specific command and server
+   data that were sent unilaterally.
+
+   The server completion result response indicates the success or
+   failure of the operation.  It is tagged with the same tag as the
+   client command which began the operation.  Thus, if more than one
+   command is in progress, the tag in a server completion response
+   identifies the command to which the response applies.  There are
+   three possible server completion responses: OK (indicating success),
+   NO (indicating failure), or BAD (indicating a protocol error such as
+   unrecognized command or command syntax error).
+
+   Servers SHOULD enforce the syntax outlined in this specification
+   strictly.  Any client command with a protocol syntax error, including
+   (but not limited to) missing or extraneous spaces or arguments,
+
+
+
+Crispin                     Standards Track                     [Page 7]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   SHOULD be rejected, and the client given a BAD server completion
+   response.
+
+   The protocol receiver of an IMAP4rev1 client reads a response line
+   from the server.  It then takes action on the response based upon the
+   first token of the response, which can be a tag, a "*", or a "+".
+
+   A client MUST be prepared to accept any server response at all times.
+   This includes server data that was not requested.  Server data SHOULD
+   be recorded, so that the client can reference its recorded copy
+   rather than sending a command to the server to request the data.  In
+   the case of certain server data, the data MUST be recorded.
+
+   This topic is discussed in greater detail in the Server Responses
+   section.
+
+2.3.    Message Attributes
+
+   In addition to message text, each message has several attributes
+   associated with it.  These attributes can be retrieved individually
+   or in conjunction with other attributes or message texts.
+
+2.3.1.  Message Numbers
+
+   Messages in IMAP4rev1 are accessed by one of two numbers; the unique
+   identifier or the message sequence number.
+
+
+2.3.1.1.        Unique Identifier (UID) Message Attribute
+
+   A 32-bit value assigned to each message, which when used with the
+   unique identifier validity value (see below) forms a 64-bit value
+   that MUST NOT refer to any other message in the mailbox or any
+   subsequent mailbox with the same name forever.  Unique identifiers
+   are assigned in a strictly ascending fashion in the mailbox; as each
+   message is added to the mailbox it is assigned a higher UID than the
+   message(s) which were added previously.  Unlike message sequence
+   numbers, unique identifiers are not necessarily contiguous.
+
+   The unique identifier of a message MUST NOT change during the
+   session, and SHOULD NOT change between sessions.  Any change of
+   unique identifiers between sessions MUST be detectable using the
+   UIDVALIDITY mechanism discussed below.  Persistent unique identifiers
+   are required for a client to resynchronize its state from a previous
+   session with the server (e.g., disconnected or offline access
+   clients); this is discussed further in [IMAP-DISC].
+
+
+
+
+
+Crispin                     Standards Track                     [Page 8]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   Associated with every mailbox are two values which aid in unique
+   identifier handling: the next unique identifier value and the unique
+   identifier validity value.
+
+   The next unique identifier value is the predicted value that will be
+   assigned to a new message in the mailbox.  Unless the unique
+   identifier validity also changes (see below), the next unique
+   identifier value MUST have the following two characteristics.  First,
+   the next unique identifier value MUST NOT change unless new messages
+   are added to the mailbox; and second, the next unique identifier
+   value MUST change whenever new messages are added to the mailbox,
+   even if those new messages are subsequently expunged.
+
+        Note: The next unique identifier value is intended to
+        provide a means for a client to determine whether any
+        messages have been delivered to the mailbox since the
+        previous time it checked this value.  It is not intended to
+        provide any guarantee that any message will have this
+        unique identifier.  A client can only assume, at the time
+        that it obtains the next unique identifier value, that
+        messages arriving after that time will have a UID greater
+        than or equal to that value.
+
+   The unique identifier validity value is sent in a UIDVALIDITY
+   response code in an OK untagged response at mailbox selection time.
+   If unique identifiers from an earlier session fail to persist in this
+   session, the unique identifier validity value MUST be greater than
+   the one used in the earlier session.
+
+        Note: Ideally, unique identifiers SHOULD persist at all
+        times.  Although this specification recognizes that failure
+        to persist can be unavoidable in certain server
+        environments, it STRONGLY ENCOURAGES message store
+        implementation techniques that avoid this problem.  For
+        example:
+
+         1) Unique identifiers MUST be strictly ascending in the
+            mailbox at all times.  If the physical message store is
+            re-ordered by a non-IMAP agent, this requires that the
+            unique identifiers in the mailbox be regenerated, since
+            the former unique identifiers are no longer strictly
+            ascending as a result of the re-ordering.
+
+         2) If the message store has no mechanism to store unique
+            identifiers, it must regenerate unique identifiers at
+            each session, and each session must have a unique
+            UIDVALIDITY value.
+
+
+
+
+Crispin                     Standards Track                     [Page 9]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+         3) If the mailbox is deleted and a new mailbox with the
+            same name is created at a later date, the server must
+            either keep track of unique identifiers from the
+            previous instance of the mailbox, or it must assign a
+            new UIDVALIDITY value to the new instance of the
+            mailbox.  A good UIDVALIDITY value to use in this case
+            is a 32-bit representation of the creation date/time of
+            the mailbox.  It is alright to use a constant such as
+            1, but only if it guaranteed that unique identifiers
+            will never be reused, even in the case of a mailbox
+            being deleted (or renamed) and a new mailbox by the
+            same name created at some future time.
+
+         4) The combination of mailbox name, UIDVALIDITY, and UID
+            must refer to a single immutable message on that server
+            forever.  In particular, the internal date, [RFC-2822]
+            size, envelope, body structure, and message texts
+            (RFC822, RFC822.HEADER, RFC822.TEXT, and all BODY[...]
+            fetch data items) must never change.  This does not
+            include message numbers, nor does it include attributes
+            that can be set by a STORE command (e.g., FLAGS).
+
+
+2.3.1.2.        Message Sequence Number Message Attribute
+
+   A relative position from 1 to the number of messages in the mailbox.
+   This position MUST be ordered by ascending unique identifier.  As
+   each new message is added, it is assigned a message sequence number
+   that is 1 higher than the number of messages in the mailbox before
+   that new message was added.
+
+   Message sequence numbers can be reassigned during the session.  For
+   example, when a message is permanently removed (expunged) from the
+   mailbox, the message sequence number for all subsequent messages is
+   decremented.  The number of messages in the mailbox is also
+   decremented.  Similarly, a new message can be assigned a message
+   sequence number that was once held by some other message prior to an
+   expunge.
+
+   In addition to accessing messages by relative position in the
+   mailbox, message sequence numbers can be used in mathematical
+   calculations.  For example, if an untagged "11 EXISTS" is received,
+   and previously an untagged "8 EXISTS" was received, three new
+   messages have arrived with message sequence numbers of 9, 10, and 11.
+   Another example, if message 287 in a 523 message mailbox has UID
+   12345, there are exactly 286 messages which have lesser UIDs and 236
+   messages which have greater UIDs.
+
+
+
+
+Crispin                     Standards Track                    [Page 10]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+2.3.2.  Flags Message Attribute
+
+   A list of zero or more named tokens associated with the message.  A
+   flag is set by its addition to this list, and is cleared by its
+   removal.  There are two types of flags in IMAP4rev1.  A flag of
+   either type can be permanent or session-only.
+
+   A system flag is a flag name that is pre-defined in this
+   specification.  All system flags begin with "\".  Certain system
+   flags (\Deleted and \Seen) have special semantics described
+   elsewhere.  The currently-defined system flags are:
+
+        \Seen
+           Message has been read
+
+        \Answered
+           Message has been answered
+
+        \Flagged
+           Message is "flagged" for urgent/special attention
+
+        \Deleted
+           Message is "deleted" for removal by later EXPUNGE
+
+        \Draft
+           Message has not completed composition (marked as a draft).
+
+        \Recent
+           Message is "recently" arrived in this mailbox.  This session
+           is the first session to have been notified about this
+           message; if the session is read-write, subsequent sessions
+           will not see \Recent set for this message.  This flag can not
+           be altered by the client.
+
+           If it is not possible to determine whether or not this
+           session is the first session to be notified about a message,
+           then that message SHOULD be considered recent.
+
+           If multiple connections have the same mailbox selected
+           simultaneously, it is undefined which of these connections
+           will see newly-arrived messages with \Recent set and which
+           will see it without \Recent set.
+
+   A keyword is defined by the server implementation.  Keywords do not
+   begin with "\".  Servers MAY permit the client to define new keywords
+   in the mailbox (see the description of the PERMANENTFLAGS response
+   code for more information).
+
+
+
+
+Crispin                     Standards Track                    [Page 11]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   A flag can be permanent or session-only on a per-flag basis.
+   Permanent flags are those which the client can add or remove from the
+   message flags permanently; that is, concurrent and subsequent
+   sessions will see any change in permanent flags.  Changes to session
+   flags are valid only in that session.
+
+        Note: The \Recent system flag is a special case of a
+        session flag.  \Recent can not be used as an argument in a
+        STORE or APPEND command, and thus can not be changed at
+        all.
+
+2.3.3.  Internal Date Message Attribute
+
+   The internal date and time of the message on the server.  This
+   is not the date and time in the [RFC-2822] header, but rather a
+   date and time which reflects when the message was received.  In
+   the case of messages delivered via [SMTP], this SHOULD be the
+   date and time of final delivery of the message as defined by
+   [SMTP].  In the case of messages delivered by the IMAP4rev1 COPY
+   command, this SHOULD be the internal date and time of the source
+   message.  In the case of messages delivered by the IMAP4rev1
+   APPEND command, this SHOULD be the date and time as specified in
+   the APPEND command description.  All other cases are
+   implementation defined.
+
+2.3.4.  [RFC-2822] Size Message Attribute
+
+   The number of octets in the message, as expressed in [RFC-2822]
+   format.
+
+2.3.5.  Envelope Structure Message Attribute
+
+   A parsed representation of the [RFC-2822] header of the message.
+   Note that the IMAP Envelope structure is not the same as an
+   [SMTP] envelope.
+
+2.3.6.  Body Structure Message Attribute
+
+   A parsed representation of the [MIME-IMB] body structure
+   information of the message.
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 12]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+2.4.    Message Texts
+
+   In addition to being able to fetch the full [RFC-2822] text of a
+   message, IMAP4rev1 permits the fetching of portions of the full
+   message text.  Specifically, it is possible to fetch the
+   [RFC-2822] message header, [RFC-2822] message body, a [MIME-IMB]
+   body part, or a [MIME-IMB] header.
+
+3.      State and Flow Diagram
+
+   Once the connection between client and server is established, an
+   IMAP4rev1 connection is in one of four states.  The initial
+   state is identified in the server greeting.  Most commands are
+   only valid in certain states.  It is a protocol error for the
+   client to attempt a command while the connection is in an
+   inappropriate state, and the server will respond with a BAD or
+   NO (depending upon server implementation) command completion
+   result.
+
+3.1.    Not Authenticated State
+
+   In the not authenticated state, the client MUST supply
+   authentication credentials before most commands will be
+   permitted.  This state is entered when a connection starts
+   unless the connection has been pre-authenticated.
+
+3.2.    Authenticated State
+
+   In the authenticated state, the client is authenticated and MUST
+   select a mailbox to access before commands that affect messages
+   will be permitted.  This state is entered when a
+   pre-authenticated connection starts, when acceptable
+   authentication credentials have been provided, after an error in
+   selecting a mailbox, or after a successful CLOSE command.
+
+3.3.    Selected State
+
+   In a selected state, a mailbox has been selected to access.
+   This state is entered when a mailbox has been successfully
+   selected.
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 13]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+3.4.    Logout State
+
+   In the logout state, the connection is being terminated.  This
+   state can be entered as a result of a client request (via the
+   LOGOUT command) or by unilateral action on the part of either
+   the client or server.
+
+   If the client requests the logout state, the server MUST send an
+   untagged BYE response and a tagged OK response to the LOGOUT
+   command before the server closes the connection; and the client
+   MUST read the tagged OK response to the LOGOUT command before
+   the client closes the connection.
+
+   A server MUST NOT unilaterally close the connection without
+   sending an untagged BYE response that contains the reason for
+   having done so.  A client SHOULD NOT unilaterally close the
+   connection, and instead SHOULD issue a LOGOUT command.  If the
+   server detects that the client has unilaterally closed the
+   connection, the server MAY omit the untagged BYE response and
+   simply close its connection.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 14]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+                   +----------------------+
+                   |connection established|
+                   +----------------------+
+                              ||
+                              \/
+            +--------------------------------------+
+            |          server greeting             |
+            +--------------------------------------+
+                      || (1)       || (2)        || (3)
+                      \/           ||            ||
+            +-----------------+    ||            ||
+            |Not Authenticated|    ||            ||
+            +-----------------+    ||            ||
+             || (7)   || (4)       ||            ||
+             ||       \/           \/            ||
+             ||     +----------------+           ||
+             ||     | Authenticated  |<=++       ||
+             ||     +----------------+  ||       ||
+             ||       || (7)   || (5)   || (6)   ||
+             ||       ||       \/       ||       ||
+             ||       ||    +--------+  ||       ||
+             ||       ||    |Selected|==++       ||
+             ||       ||    +--------+           ||
+             ||       ||       || (7)            ||
+             \/       \/       \/                \/
+            +--------------------------------------+
+            |               Logout                 |
+            +--------------------------------------+
+                              ||
+                              \/
+                +-------------------------------+
+                |both sides close the connection|
+                +-------------------------------+
+
+         (1) connection without pre-authentication (OK greeting)
+         (2) pre-authenticated connection (PREAUTH greeting)
+         (3) rejected connection (BYE greeting)
+         (4) successful LOGIN or AUTHENTICATE command
+         (5) successful SELECT or EXAMINE command
+         (6) CLOSE command, or failed SELECT or EXAMINE command
+         (7) LOGOUT command, server shutdown, or connection closed
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 15]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+4.      Data Formats
+
+   IMAP4rev1 uses textual commands and responses.  Data in
+   IMAP4rev1 can be in one of several forms: atom, number, string,
+   parenthesized list, or NIL.  Note that a particular data item
+   may take more than one form; for example, a data item defined as
+   using "astring" syntax may be either an atom or a string.
+
+4.1.    Atom
+
+   An atom consists of one or more non-special characters.
+
+4.2.    Number
+
+   A number consists of one or more digit characters, and
+   represents a numeric value.
+
+4.3.    String
+
+   A string is in one of two forms: either literal or quoted
+   string.  The literal form is the general form of string.  The
+   quoted string form is an alternative that avoids the overhead of
+   processing a literal at the cost of limitations of characters
+   which may be used.
+
+   A literal is a sequence of zero or more octets (including CR and
+   LF), prefix-quoted with an octet count in the form of an open
+   brace ("{"), the number of octets, close brace ("}"), and CRLF.
+   In the case of literals transmitted from server to client, the
+   CRLF is immediately followed by the octet data.  In the case of
+   literals transmitted from client to server, the client MUST wait
+   to receive a command continuation request (described later in
+   this document) before sending the octet data (and the remainder
+   of the command).
+
+   A quoted string is a sequence of zero or more 7-bit characters,
+   excluding CR and LF, with double quote (<">) characters at each
+   end.
+
+   The empty string is represented as either "" (a quoted string
+   with zero characters between double quotes) or as {0} followed
+   by CRLF (a literal with an octet count of 0).
+
+     Note: Even if the octet count is 0, a client transmitting a
+     literal MUST wait to receive a command continuation request.
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 16]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+4.3.1.  8-bit and Binary Strings
+
+   8-bit textual and binary mail is supported through the use of a
+   [MIME-IMB] content transfer encoding.  IMAP4rev1 implementations MAY
+   transmit 8-bit or multi-octet characters in literals, but SHOULD do
+   so only when the [CHARSET] is identified.
+
+   Although a BINARY body encoding is defined, unencoded binary strings
+   are not permitted.  A "binary string" is any string with NUL
+   characters.  Implementations MUST encode binary data into a textual
+   form, such as BASE64, before transmitting the data.  A string with an
+   excessive amount of CTL characters MAY also be considered to be
+   binary.
+
+4.4.    Parenthesized List
+
+   Data structures are represented as a "parenthesized list"; a sequence
+   of data items, delimited by space, and bounded at each end by
+   parentheses.  A parenthesized list can contain other parenthesized
+   lists, using multiple levels of parentheses to indicate nesting.
+
+   The empty list is represented as () -- a parenthesized list with no
+   members.
+
+4.5.    NIL
+
+   The special form "NIL" represents the non-existence of a particular
+   data item that is represented as a string or parenthesized list, as
+   distinct from the empty string "" or the empty parenthesized list ().
+
+        Note: NIL is never used for any data item which takes the
+        form of an atom.  For example, a mailbox name of "NIL" is a
+        mailbox named NIL as opposed to a non-existent mailbox
+        name.  This is because mailbox uses "astring" syntax which
+        is an atom or a string.  Conversely, an addr-name of NIL is
+        a non-existent personal name, because addr-name uses
+        "nstring" syntax which is NIL or a string, but never an
+        atom.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 17]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+5.      Operational Considerations
+
+   The following rules are listed here to ensure that all IMAP4rev1
+   implementations interoperate properly.
+
+5.1.    Mailbox Naming
+
+   Mailbox names are 7-bit.  Client implementations MUST NOT attempt to
+   create 8-bit mailbox names, and SHOULD interpret any 8-bit mailbox
+   names returned by LIST or LSUB as UTF-8.  Server implementations
+   SHOULD prohibit the creation of 8-bit mailbox names, and SHOULD NOT
+   return 8-bit mailbox names in LIST or LSUB.  See section 5.1.3 for
+   more information on how to represent non-ASCII mailbox names.
+
+        Note: 8-bit mailbox names were undefined in earlier
+        versions of this protocol.  Some sites used a local 8-bit
+        character set to represent non-ASCII mailbox names.  Such
+        usage is not interoperable, and is now formally deprecated.
+
+   The case-insensitive mailbox name INBOX is a special name reserved to
+   mean "the primary mailbox for this user on this server".  The
+   interpretation of all other names is implementation-dependent.
+
+   In particular, this specification takes no position on case
+   sensitivity in non-INBOX mailbox names.  Some server implementations
+   are fully case-sensitive; others preserve case of a newly-created
+   name but otherwise are case-insensitive; and yet others coerce names
+   to a particular case.  Client implementations MUST interact with any
+   of these.  If a server implementation interprets non-INBOX mailbox
+   names as case-insensitive, it MUST treat names using the
+   international naming convention specially as described in section
+   5.1.3.
+
+   There are certain client considerations when creating a new mailbox
+   name:
+
+   1)    Any character which is one of the atom-specials (see the Formal
+         Syntax) will require that the mailbox name be represented as a
+         quoted string or literal.
+
+   2)    CTL and other non-graphic characters are difficult to represent
+         in a user interface and are best avoided.
+
+   3)    Although the list-wildcard characters ("%" and "*") are valid
+         in a mailbox name, it is difficult to use such mailbox names
+         with the LIST and LSUB commands due to the conflict with
+         wildcard interpretation.
+
+
+
+
+Crispin                     Standards Track                    [Page 18]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   4)    Usually, a character (determined by the server implementation)
+         is reserved to delimit levels of hierarchy.
+
+   5)    Two characters, "#" and "&", have meanings by convention, and
+         should be avoided except when used in that convention.
+
+5.1.1.  Mailbox Hierarchy Naming
+
+   If it is desired to export hierarchical mailbox names, mailbox names
+   MUST be left-to-right hierarchical using a single character to
+   separate levels of hierarchy.  The same hierarchy separator character
+   is used for all levels of hierarchy within a single name.
+
+5.1.2.  Mailbox Namespace Naming Convention
+
+   By convention, the first hierarchical element of any mailbox name
+   which begins with "#" identifies the "namespace" of the remainder of
+   the name.  This makes it possible to disambiguate between different
+   types of mailbox stores, each of which have their own namespaces.
+
+        For example, implementations which offer access to USENET
+        newsgroups MAY use the "#news" namespace to partition the
+        USENET newsgroup namespace from that of other mailboxes.
+        Thus, the comp.mail.misc newsgroup would have a mailbox
+        name of "#news.comp.mail.misc", and the name
+        "comp.mail.misc" can refer to a different object (e.g., a
+        user's private mailbox).
+
+5.1.3.  Mailbox International Naming Convention
+
+   By convention, international mailbox names in IMAP4rev1 are specified
+   using a modified version of the UTF-7 encoding described in [UTF-7].
+   Modified UTF-7 may also be usable in servers that implement an
+   earlier version of this protocol.
+
+   In modified UTF-7, printable US-ASCII characters, except for "&",
+   represent themselves; that is, characters with octet values 0x20-0x25
+   and 0x27-0x7e.  The character "&" (0x26) is represented by the
+   two-octet sequence "&-".
+
+   All other characters (octet values 0x00-0x1f and 0x7f-0xff) are
+   represented in modified BASE64, with a further modification from
+   [UTF-7] that "," is used instead of "/".  Modified BASE64 MUST NOT be
+   used to represent any printing US-ASCII character which can represent
+   itself.
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 19]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   "&" is used to shift to modified BASE64 and "-" to shift back to
+   US-ASCII.  There is no implicit shift from BASE64 to US-ASCII, and
+   null shifts ("-&" while in BASE64; note that "&-" while in US-ASCII
+   means "&") are not permitted.  However, all names start in US-ASCII,
+   and MUST end in US-ASCII; that is, a name that ends with a non-ASCII
+   ISO-10646 character MUST end with a "-").
+
+   The purpose of these modifications is to correct the following
+   problems with UTF-7:
+
+      1) UTF-7 uses the "+" character for shifting; this conflicts with
+         the common use of "+" in mailbox names, in particular USENET
+         newsgroup names.
+
+      2) UTF-7's encoding is BASE64 which uses the "/" character; this
+         conflicts with the use of "/" as a popular hierarchy delimiter.
+
+      3) UTF-7 prohibits the unencoded usage of "\"; this conflicts with
+         the use of "\" as a popular hierarchy delimiter.
+
+      4) UTF-7 prohibits the unencoded usage of "~"; this conflicts with
+         the use of "~" in some servers as a home directory indicator.
+
+      5) UTF-7 permits multiple alternate forms to represent the same
+         string; in particular, printable US-ASCII characters can be
+         represented in encoded form.
+
+      Although modified UTF-7 is a convention, it establishes certain
+      requirements on server handling of any mailbox name with an
+      embedded "&" character.  In particular, server implementations
+      MUST preserve the exact form of the modified BASE64 portion of a
+      modified UTF-7 name and treat that text as case-sensitive, even if
+      names are otherwise case-insensitive or case-folded.
+
+      Server implementations SHOULD verify that any mailbox name with an
+      embedded "&" character, used as an argument to CREATE, is: in the
+      correctly modified UTF-7 syntax, has no superfluous shifts, and
+      has no encoding in modified BASE64 of any printing US-ASCII
+      character which can represent itself.  However, client
+      implementations MUST NOT depend upon the server doing this, and
+      SHOULD NOT attempt to create a mailbox name with an embedded "&"
+      character unless it complies with the modified UTF-7 syntax.
+
+      Server implementations which export a mail store that does not
+      follow the modified UTF-7 convention MUST convert to modified
+      UTF-7 any mailbox name that contains either non-ASCII characters
+      or the "&" character.
+
+
+
+
+Crispin                     Standards Track                    [Page 20]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+           For example, here is a mailbox name which mixes English,
+           Chinese, and Japanese text:
+           ~peter/mail/&U,BTFw-/&ZeVnLIqe-
+
+           For example, the string "&Jjo!" is not a valid mailbox
+           name because it does not contain a shift to US-ASCII
+           before the "!".  The correct form is "&Jjo-!".  The
+           string "&U,BTFw-&ZeVnLIqe-" is not permitted because it
+           contains a superfluous shift.  The correct form is
+           "&U,BTF2XlZyyKng-".
+
+5.2.    Mailbox Size and Message Status Updates
+
+   At any time, a server can send data that the client did not request.
+   Sometimes, such behavior is REQUIRED.  For example, agents other than
+   the server MAY add messages to the mailbox (e.g., new message
+   delivery), change the flags of the messages in the mailbox (e.g.,
+   simultaneous access to the same mailbox by multiple agents), or even
+   remove messages from the mailbox.  A server MUST send mailbox size
+   updates automatically if a mailbox size change is observed during the
+   processing of a command.  A server SHOULD send message flag updates
+   automatically, without requiring the client to request such updates
+   explicitly.
+
+   Special rules exist for server notification of a client about the
+   removal of messages to prevent synchronization errors; see the
+   description of the EXPUNGE response for more detail.  In particular,
+   it is NOT permitted to send an EXISTS response that would reduce the
+   number of messages in the mailbox; only the EXPUNGE response can do
+   this.
+
+   Regardless of what implementation decisions a client makes on
+   remembering data from the server, a client implementation MUST record
+   mailbox size updates.  It MUST NOT assume that any command after the
+   initial mailbox selection will return the size of the mailbox.
+
+5.3.    Response when no Command in Progress
+
+   Server implementations are permitted to send an untagged response
+   (except for EXPUNGE) while there is no command in progress.  Server
+   implementations that send such responses MUST deal with flow control
+   considerations.  Specifically, they MUST either (1) verify that the
+   size of the data does not exceed the underlying transport's available
+   window size, or (2) use non-blocking writes.
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 21]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+5.4.    Autologout Timer
+
+   If a server has an inactivity autologout timer, the duration of that
+   timer MUST be at least 30 minutes.  The receipt of ANY command from
+   the client during that interval SHOULD suffice to reset the
+   autologout timer.
+
+5.5.    Multiple Commands in Progress
+
+   The client MAY send another command without waiting for the
+   completion result response of a command, subject to ambiguity rules
+   (see below) and flow control constraints on the underlying data
+   stream.  Similarly, a server MAY begin processing another command
+   before processing the current command to completion, subject to
+   ambiguity rules.  However, any command continuation request responses
+   and command continuations MUST be negotiated before any subsequent
+   command is initiated.
+
+   The exception is if an ambiguity would result because of a command
+   that would affect the results of other commands.  Clients MUST NOT
+   send multiple commands without waiting if an ambiguity would result.
+   If the server detects a possible ambiguity, it MUST execute commands
+   to completion in the order given by the client.
+
+   The most obvious example of ambiguity is when a command would affect
+   the results of another command, e.g., a FETCH of a message's flags
+   and a STORE of that same message's flags.
+
+   A non-obvious ambiguity occurs with commands that permit an untagged
+   EXPUNGE response (commands other than FETCH, STORE, and SEARCH),
+   since an untagged EXPUNGE response can invalidate sequence numbers in
+   a subsequent command.  This is not a problem for FETCH, STORE, or
+   SEARCH commands because servers are prohibited from sending EXPUNGE
+   responses while any of those commands are in progress.  Therefore, if
+   the client sends any command other than FETCH, STORE, or SEARCH, it
+   MUST wait for the completion result response before sending a command
+   with message sequence numbers.
+
+        Note: UID FETCH, UID STORE, and UID SEARCH are different
+        commands from FETCH, STORE, and SEARCH.  If the client
+        sends a UID command, it must wait for a completion result
+        response before sending a command with message sequence
+        numbers.
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 22]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   For example, the following non-waiting command sequences are invalid:
+
+      FETCH + NOOP + STORE
+      STORE + COPY + FETCH
+      COPY + COPY
+      CHECK + FETCH
+
+   The following are examples of valid non-waiting command sequences:
+
+      FETCH + STORE + SEARCH + CHECK
+      STORE + COPY + EXPUNGE
+
+      UID SEARCH + UID SEARCH may be valid or invalid as a non-waiting
+      command sequence, depending upon whether or not the second UID
+      SEARCH contains message sequence numbers.
+
+6.      Client Commands
+
+   IMAP4rev1 commands are described in this section.  Commands are
+   organized by the state in which the command is permitted.  Commands
+   which are permitted in multiple states are listed in the minimum
+   permitted state (for example, commands valid in authenticated and
+   selected state are listed in the authenticated state commands).
+
+   Command arguments, identified by "Arguments:" in the command
+   descriptions below, are described by function, not by syntax.  The
+   precise syntax of command arguments is described in the Formal Syntax
+   section.
+
+   Some commands cause specific server responses to be returned; these
+   are identified by "Responses:" in the command descriptions below.
+   See the response descriptions in the Responses section for
+   information on these responses, and the Formal Syntax section for the
+   precise syntax of these responses.  It is possible for server data to
+   be transmitted as a result of any command.  Thus, commands that do
+   not specifically require server data specify "no specific responses
+   for this command" instead of "none".
+
+   The "Result:" in the command description refers to the possible
+   tagged status responses to a command, and any special interpretation
+   of these status responses.
+
+   The state of a connection is only changed by successful commands
+   which are documented as changing state.  A rejected command (BAD
+   response) never changes the state of the connection or of the
+   selected mailbox.  A failed command (NO response) generally does not
+   change the state of the connection or of the selected mailbox; the
+   exception being the SELECT and EXAMINE commands.
+
+
+
+Crispin                     Standards Track                    [Page 23]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.1.    Client Commands - Any State
+
+   The following commands are valid in any state: CAPABILITY, NOOP, and
+   LOGOUT.
+
+6.1.1.  CAPABILITY Command
+
+   Arguments:  none
+
+   Responses:  REQUIRED untagged response: CAPABILITY
+
+   Result:     OK - capability completed
+               BAD - command unknown or arguments invalid
+
+      The CAPABILITY command requests a listing of capabilities that the
+      server supports.  The server MUST send a single untagged
+      CAPABILITY response with "IMAP4rev1" as one of the listed
+      capabilities before the (tagged) OK response.
+
+      A capability name which begins with "AUTH=" indicates that the
+      server supports that particular authentication mechanism.  All
+      such names are, by definition, part of this specification.  For
+      example, the authorization capability for an experimental
+      "blurdybloop" authenticator would be "AUTH=XBLURDYBLOOP" and not
+      "XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".
+
+      Other capability names refer to extensions, revisions, or
+      amendments to this specification.  See the documentation of the
+      CAPABILITY response for additional information.  No capabilities,
+      beyond the base IMAP4rev1 set defined in this specification, are
+      enabled without explicit client action to invoke the capability.
+
+      Client and server implementations MUST implement the STARTTLS,
+      LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
+      capabilities.  See the Security Considerations section for
+      important information.
+
+      See the section entitled "Client Commands -
+      Experimental/Expansion" for information about the form of site or
+      implementation-specific capabilities.
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 24]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   Example:    C: abcd CAPABILITY
+               S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI
+               LOGINDISABLED
+               S: abcd OK CAPABILITY completed
+               C: efgh STARTTLS
+               S: efgh OK STARTLS completed
+               <TLS negotiation, further commands are under [TLS] layer>
+               C: ijkl CAPABILITY
+               S: * CAPABILITY IMAP4rev1 AUTH=GSSAPI AUTH=PLAIN
+               S: ijkl OK CAPABILITY completed
+
+
+6.1.2.  NOOP Command
+
+   Arguments:  none
+
+   Responses:  no specific responses for this command (but see below)
+
+   Result:     OK - noop completed
+               BAD - command unknown or arguments invalid
+
+      The NOOP command always succeeds.  It does nothing.
+
+      Since any command can return a status update as untagged data, the
+      NOOP command can be used as a periodic poll for new messages or
+      message status updates during a period of inactivity (this is the
+      preferred method to do this).  The NOOP command can also be used
+      to reset any inactivity autologout timer on the server.
+
+   Example:    C: a002 NOOP
+               S: a002 OK NOOP completed
+                  . . .
+               C: a047 NOOP
+               S: * 22 EXPUNGE
+               S: * 23 EXISTS
+               S: * 3 RECENT
+               S: * 14 FETCH (FLAGS (\Seen \Deleted))
+               S: a047 OK NOOP completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 25]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.1.3.  LOGOUT Command
+
+   Arguments:  none
+
+   Responses:  REQUIRED untagged response: BYE
+
+   Result:     OK - logout completed
+               BAD - command unknown or arguments invalid
+
+      The LOGOUT command informs the server that the client is done with
+      the connection.  The server MUST send a BYE untagged response
+      before the (tagged) OK response, and then close the network
+      connection.
+
+   Example:    C: A023 LOGOUT
+               S: * BYE IMAP4rev1 Server logging out
+               S: A023 OK LOGOUT completed
+               (Server and client then close the connection)
+
+6.2.    Client Commands - Not Authenticated State
+
+   In the not authenticated state, the AUTHENTICATE or LOGIN command
+   establishes authentication and enters the authenticated state.  The
+   AUTHENTICATE command provides a general mechanism for a variety of
+   authentication techniques, privacy protection, and integrity
+   checking; whereas the LOGIN command uses a traditional user name and
+   plaintext password pair and has no means of establishing privacy
+   protection or integrity checking.
+
+   The STARTTLS command is an alternate form of establishing session
+   privacy protection and integrity checking, but does not establish
+   authentication or enter the authenticated state.
+
+   Server implementations MAY allow access to certain mailboxes without
+   establishing authentication.  This can be done by means of the
+   ANONYMOUS [SASL] authenticator described in [ANONYMOUS].  An older
+   convention is a LOGIN command using the userid "anonymous"; in this
+   case, a password is required although the server may choose to accept
+   any password.  The restrictions placed on anonymous users are
+   implementation-dependent.
+
+   Once authenticated (including as anonymous), it is not possible to
+   re-enter not authenticated state.
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 26]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+   the following commands are valid in the not authenticated state:
+   STARTTLS, AUTHENTICATE and LOGIN.  See the Security Considerations
+   section for important information about these commands.
+
+6.2.1.  STARTTLS Command
+
+   Arguments:  none
+
+   Responses:  no specific response for this command
+
+   Result:     OK - starttls completed, begin TLS negotiation
+               BAD - command unknown or arguments invalid
+
+      A [TLS] negotiation begins immediately after the CRLF at the end
+      of the tagged OK response from the server.  Once a client issues a
+      STARTTLS command, it MUST NOT issue further commands until a
+      server response is seen and the [TLS] negotiation is complete.
+
+      The server remains in the non-authenticated state, even if client
+      credentials are supplied during the [TLS] negotiation.  This does
+      not preclude an authentication mechanism such as EXTERNAL (defined
+      in [SASL]) from using client identity determined by the [TLS]
+      negotiation.
+
+      Once [TLS] has been started, the client MUST discard cached
+      information about server capabilities and SHOULD re-issue the
+      CAPABILITY command.  This is necessary to protect against man-in-
+      the-middle attacks which alter the capabilities list prior to
+      STARTTLS.  The server MAY advertise different capabilities after
+      STARTTLS.
+
+   Example:    C: a001 CAPABILITY
+               S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
+               S: a001 OK CAPABILITY completed
+               C: a002 STARTTLS
+               S: a002 OK Begin TLS negotiation now
+               <TLS negotiation, further commands are under [TLS] layer>
+               C: a003 CAPABILITY
+               S: * CAPABILITY IMAP4rev1 AUTH=PLAIN
+               S: a003 OK CAPABILITY completed
+               C: a004 LOGIN joe password
+               S: a004 OK LOGIN completed
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 27]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.2.2.  AUTHENTICATE Command
+
+   Arguments:  authentication mechanism name
+
+   Responses:  continuation data can be requested
+
+   Result:     OK - authenticate completed, now in authenticated state
+               NO - authenticate failure: unsupported authentication
+                    mechanism, credentials rejected
+               BAD - command unknown or arguments invalid,
+                    authentication exchange cancelled
+
+      The AUTHENTICATE command indicates a [SASL] authentication
+      mechanism to the server.  If the server supports the requested
+      authentication mechanism, it performs an authentication protocol
+      exchange to authenticate and identify the client.  It MAY also
+      negotiate an OPTIONAL security layer for subsequent protocol
+      interactions.  If the requested authentication mechanism is not
+      supported, the server SHOULD reject the AUTHENTICATE command by
+      sending a tagged NO response.
+
+      The AUTHENTICATE command does not support the optional "initial
+      response" feature of [SASL].  Section 5.1 of [SASL] specifies how
+      to handle an authentication mechanism which uses an initial
+      response.
+
+      The service name specified by this protocol's profile of [SASL] is
+      "imap".
+
+      The authentication protocol exchange consists of a series of
+      server challenges and client responses that are specific to the
+      authentication mechanism.  A server challenge consists of a
+      command continuation request response with the "+" token followed
+      by a BASE64 encoded string.  The client response consists of a
+      single line consisting of a BASE64 encoded string.  If the client
+      wishes to cancel an authentication exchange, it issues a line
+      consisting of a single "*".  If the server receives such a
+      response, it MUST reject the AUTHENTICATE command by sending a
+      tagged BAD response.
+
+      If a security layer is negotiated through the [SASL]
+      authentication exchange, it takes effect immediately following the
+      CRLF that concludes the authentication exchange for the client,
+      and the CRLF of the tagged OK response for the server.
+
+      While client and server implementations MUST implement the
+      AUTHENTICATE command itself, it is not required to implement any
+      authentication mechanisms other than the PLAIN mechanism described
+
+
+
+Crispin                     Standards Track                    [Page 28]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      in [IMAP-TLS].  Also, an authentication mechanism is not required
+      to support any security layers.
+
+           Note: a server implementation MUST implement a
+           configuration in which it does NOT permit any plaintext
+           password mechanisms, unless either the STARTTLS command
+           has been negotiated or some other mechanism that
+           protects the session from password snooping has been
+           provided.  Server sites SHOULD NOT use any configuration
+           which permits a plaintext password mechanism without
+           such a protection mechanism against password snooping.
+           Client and server implementations SHOULD implement
+           additional [SASL] mechanisms that do not use plaintext
+           passwords, such the GSSAPI mechanism described in [SASL]
+           and/or the [DIGEST-MD5] mechanism.
+
+      Servers and clients can support multiple authentication
+      mechanisms.  The server SHOULD list its supported authentication
+      mechanisms in the response to the CAPABILITY command so that the
+      client knows which authentication mechanisms to use.
+
+      A server MAY include a CAPABILITY response code in the tagged OK
+      response of a successful AUTHENTICATE command in order to send
+      capabilities automatically.  It is unnecessary for a client to
+      send a separate CAPABILITY command if it recognizes these
+      automatic capabilities.  This should only be done if a security
+      layer was not negotiated by the AUTHENTICATE command, because the
+      tagged OK response as part of an AUTHENTICATE command is not
+      protected by encryption/integrity checking.  [SASL] requires the
+      client to re-issue a CAPABILITY command in this case.
+
+      If an AUTHENTICATE command fails with a NO response, the client
+      MAY try another authentication mechanism by issuing another
+      AUTHENTICATE command.  It MAY also attempt to authenticate by
+      using the LOGIN command (see section 6.2.3 for more detail).  In
+      other words, the client MAY request authentication types in
+      decreasing order of preference, with the LOGIN command as a last
+      resort.
+
+      The authorization identity passed from the client to the server
+      during the authentication exchange is interpreted by the server as
+      the user name whose privileges the client is requesting.
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 29]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   Example:    S: * OK IMAP4rev1 Server
+               C: A001 AUTHENTICATE GSSAPI
+               S: +
+               C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw
+                  MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0
+                  b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW
+                  Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA
+                  cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX
+                  AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y
+                  C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb
+                  I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi
+                  vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL
+                  pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n
+                  FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE
+                  NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx
+                  O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB
+                  vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg==
+               S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC
+                  AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0
+                  uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg==
+               C:
+               S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe
+                  ceP2CWY0SR0fAQAgAAQEBAQ=
+               C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP
+                  wkhbfa2QteAQAgAG1yYwE=
+               S: A001 OK GSSAPI authentication successful
+
+        Note: The line breaks within server challenges and client
+        responses are for editorial clarity and are not in real
+        authenticators.
+
+
+6.2.3.  LOGIN Command
+
+   Arguments:  user name
+               password
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - login completed, now in authenticated state
+               NO - login failure: user name or password rejected
+               BAD - command unknown or arguments invalid
+
+      The LOGIN command identifies the client to the server and carries
+      the plaintext password authenticating this user.
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 30]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      A server MAY include a CAPABILITY response code in the tagged OK
+      response to a successful LOGIN command in order to send
+      capabilities automatically.  It is unnecessary for a client to
+      send a separate CAPABILITY command if it recognizes these
+      automatic capabilities.
+
+   Example:    C: a001 LOGIN SMITH SESAME
+               S: a001 OK LOGIN completed
+
+        Note: Use of the LOGIN command over an insecure network
+        (such as the Internet) is a security risk, because anyone
+        monitoring network traffic can obtain plaintext passwords.
+        The LOGIN command SHOULD NOT be used except as a last
+        resort, and it is recommended that client implementations
+        have a means to disable any automatic use of the LOGIN
+        command.
+
+        Unless either the STARTTLS command has been negotiated or
+        some other mechanism that protects the session from
+        password snooping has been provided, a server
+        implementation MUST implement a configuration in which it
+        advertises the LOGINDISABLED capability and does NOT permit
+        the LOGIN command.  Server sites SHOULD NOT use any
+        configuration which permits the LOGIN command without such
+        a protection mechanism against password snooping.  A client
+        implementation MUST NOT send a LOGIN command if the
+        LOGINDISABLED capability is advertised.
+
+6.3.    Client Commands - Authenticated State
+
+   In the authenticated state, commands that manipulate mailboxes as
+   atomic entities are permitted.  Of these commands, the SELECT and
+   EXAMINE commands will select a mailbox for access and enter the
+   selected state.
+
+   In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+   the following commands are valid in the authenticated state: SELECT,
+   EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB,
+   STATUS, and APPEND.
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 31]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.3.1.  SELECT Command
+
+   Arguments:  mailbox name
+
+   Responses:  REQUIRED untagged responses: FLAGS, EXISTS, RECENT
+               REQUIRED OK untagged responses:  UNSEEN,  PERMANENTFLAGS,
+               UIDNEXT, UIDVALIDITY
+
+   Result:     OK - select completed, now in selected state
+               NO - select failure, now in authenticated state: no
+                    such mailbox, can't access mailbox
+               BAD - command unknown or arguments invalid
+
+      The SELECT command selects a mailbox so that messages in the
+      mailbox can be accessed.  Before returning an OK to the client,
+      the server MUST send the following untagged data to the client.
+      Note that earlier versions of this protocol only required the
+      FLAGS, EXISTS, and RECENT untagged data; consequently, client
+      implementations SHOULD implement default behavior for missing data
+      as discussed with the individual item.
+
+         FLAGS       Defined flags in the mailbox.  See the description
+                     of the FLAGS response for more detail.
+
+         <n> EXISTS  The number of messages in the mailbox.  See the
+                     description of the EXISTS response for more detail.
+
+         <n> RECENT  The number of messages with the \Recent flag set.
+                     See the description of the RECENT response for more
+                     detail.
+
+         OK [UNSEEN <n>]
+                     The message sequence number of the first unseen
+                     message in the mailbox.  If this is missing, the
+                     client can not make any assumptions about the first
+                     unseen message in the mailbox, and needs to issue a
+                     SEARCH command if it wants to find it.
+
+         OK [PERMANENTFLAGS (<list of flags>)]
+                     A list of message flags that the client can change
+                     permanently.  If this is missing, the client should
+                     assume that all flags can be changed permanently.
+
+         OK [UIDNEXT <n>]
+                     The next unique identifier value.  Refer to section
+                     2.3.1.1 for more information.  If this is missing,
+                     the client can not make any assumptions about the
+                     next unique identifier value.
+
+
+
+Crispin                     Standards Track                    [Page 32]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+         OK [UIDVALIDITY <n>]
+                     The unique identifier validity value.  Refer to
+                     section 2.3.1.1 for more information.  If this is
+                     missing, the server does not support unique
+                     identifiers.
+
+      Only one mailbox can be selected at a time in a connection;
+      simultaneous access to multiple mailboxes requires multiple
+      connections.  The SELECT command automatically deselects any
+      currently selected mailbox before attempting the new selection.
+      Consequently, if a mailbox is selected and a SELECT command that
+      fails is attempted, no mailbox is selected.
+
+      If the client is permitted to modify the mailbox, the server
+      SHOULD prefix the text of the tagged OK response with the
+      "[READ-WRITE]" response code.
+
+      If the client is not permitted to modify the mailbox but is
+      permitted read access, the mailbox is selected as read-only, and
+      the server MUST prefix the text of the tagged OK response to
+      SELECT with the "[READ-ONLY]" response code.  Read-only access
+      through SELECT differs from the EXAMINE command in that certain
+      read-only mailboxes MAY permit the change of permanent state on a
+      per-user (as opposed to global) basis.  Netnews messages marked in
+      a server-based .newsrc file are an example of such per-user
+      permanent state that can be modified with read-only mailboxes.
+
+   Example:    C: A142 SELECT INBOX
+               S: * 172 EXISTS
+               S: * 1 RECENT
+               S: * OK [UNSEEN 12] Message 12 is first unseen
+               S: * OK [UIDVALIDITY 3857529045] UIDs valid
+               S: * OK [UIDNEXT 4392] Predicted next UID
+               S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+               S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+               S: A142 OK [READ-WRITE] SELECT completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 33]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.3.2.  EXAMINE Command
+
+   Arguments:  mailbox name
+
+   Responses:  REQUIRED untagged responses: FLAGS, EXISTS, RECENT
+               REQUIRED OK untagged responses:  UNSEEN,  PERMANENTFLAGS,
+               UIDNEXT, UIDVALIDITY
+
+   Result:     OK - examine completed, now in selected state
+               NO - examine failure, now in authenticated state: no
+                    such mailbox, can't access mailbox
+               BAD - command unknown or arguments invalid
+
+      The EXAMINE command is identical to SELECT and returns the same
+      output; however, the selected mailbox is identified as read-only.
+      No changes to the permanent state of the mailbox, including
+      per-user state, are permitted; in particular, EXAMINE MUST NOT
+      cause messages to lose the \Recent flag.
+
+      The text of the tagged OK response to the EXAMINE command MUST
+      begin with the "[READ-ONLY]" response code.
+
+   Example:    C: A932 EXAMINE blurdybloop
+               S: * 17 EXISTS
+               S: * 2 RECENT
+               S: * OK [UNSEEN 8] Message 8 is first unseen
+               S: * OK [UIDVALIDITY 3857529045] UIDs valid
+               S: * OK [UIDNEXT 4392] Predicted next UID
+               S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+               S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
+               S: A932 OK [READ-ONLY] EXAMINE completed
+
+
+6.3.3.  CREATE Command
+
+   Arguments:  mailbox name
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - create completed
+               NO - create failure: can't create mailbox with that name
+               BAD - command unknown or arguments invalid
+
+      The CREATE command creates a mailbox with the given name.  An OK
+      response is returned only if a new mailbox with that name has been
+      created.  It is an error to attempt to create INBOX or a mailbox
+      with a name that refers to an extant mailbox.  Any error in
+      creation will return a tagged NO response.
+
+
+
+Crispin                     Standards Track                    [Page 34]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      If the mailbox name is suffixed with the server's hierarchy
+      separator character (as returned from the server by a LIST
+      command), this is a declaration that the client intends to create
+      mailbox names under this name in the hierarchy.  Server
+      implementations that do not require this declaration MUST ignore
+      the declaration.  In any case, the name created is without the
+      trailing hierarchy delimiter.
+
+      If the server's hierarchy separator character appears elsewhere in
+      the name, the server SHOULD create any superior hierarchical names
+      that are needed for the CREATE command to be successfully
+      completed.  In other words, an attempt to create "foo/bar/zap" on
+      a server in which "/" is the hierarchy separator character SHOULD
+      create foo/ and foo/bar/ if they do not already exist.
+
+      If a new mailbox is created with the same name as a mailbox which
+      was deleted, its unique identifiers MUST be greater than any
+      unique identifiers used in the previous incarnation of the mailbox
+      UNLESS the new incarnation has a different unique identifier
+      validity value.  See the description of the UID command for more
+      detail.
+
+   Example:    C: A003 CREATE owatagusiam/
+               S: A003 OK CREATE completed
+               C: A004 CREATE owatagusiam/blurdybloop
+               S: A004 OK CREATE completed
+
+        Note: The interpretation of this example depends on whether
+        "/" was returned as the hierarchy separator from LIST.  If
+        "/" is the hierarchy separator, a new level of hierarchy
+        named "owatagusiam" with a member called "blurdybloop" is
+        created.  Otherwise, two mailboxes at the same hierarchy
+        level are created.
+
+
+6.3.4.  DELETE Command
+
+   Arguments:  mailbox name
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - delete completed
+               NO - delete failure: can't delete mailbox with that name
+               BAD - command unknown or arguments invalid
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 35]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      The DELETE command permanently removes the mailbox with the given
+      name.  A tagged OK response is returned only if the mailbox has
+      been deleted.  It is an error to attempt to delete INBOX or a
+      mailbox name that does not exist.
+
+      The DELETE command MUST NOT remove inferior hierarchical names.
+      For example, if a mailbox "foo" has an inferior "foo.bar"
+      (assuming "." is the hierarchy delimiter character), removing
+      "foo" MUST NOT remove "foo.bar".  It is an error to attempt to
+      delete a name that has inferior hierarchical names and also has
+      the \Noselect mailbox name attribute (see the description of the
+      LIST response for more details).
+
+      It is permitted to delete a name that has inferior hierarchical
+      names and does not have the \Noselect mailbox name attribute.  In
+      this case, all messages in that mailbox are removed, and the name
+      will acquire the \Noselect mailbox name attribute.
+
+      The value of the highest-used unique identifier of the deleted
+      mailbox MUST be preserved so that a new mailbox created with the
+      same name will not reuse the identifiers of the former
+      incarnation, UNLESS the new incarnation has a different unique
+      identifier validity value.  See the description of the UID command
+      for more detail.
+
+   Examples:   C: A682 LIST "" *
+               S: * LIST () "/" blurdybloop
+               S: * LIST (\Noselect) "/" foo
+               S: * LIST () "/" foo/bar
+               S: A682 OK LIST completed
+               C: A683 DELETE blurdybloop
+               S: A683 OK DELETE completed
+               C: A684 DELETE foo
+               S: A684 NO Name "foo" has inferior hierarchical names
+               C: A685 DELETE foo/bar
+               S: A685 OK DELETE Completed
+               C: A686 LIST "" *
+               S: * LIST (\Noselect) "/" foo
+               S: A686 OK LIST completed
+               C: A687 DELETE foo
+               S: A687 OK DELETE Completed
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 36]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+               C: A82 LIST "" *
+               S: * LIST () "." blurdybloop
+               S: * LIST () "." foo
+               S: * LIST () "." foo.bar
+               S: A82 OK LIST completed
+               C: A83 DELETE blurdybloop
+               S: A83 OK DELETE completed
+               C: A84 DELETE foo
+               S: A84 OK DELETE Completed
+               C: A85 LIST "" *
+               S: * LIST () "." foo.bar
+               S: A85 OK LIST completed
+               C: A86 LIST "" %
+               S: * LIST (\Noselect) "." foo
+               S: A86 OK LIST completed
+
+
+6.3.5.  RENAME Command
+
+   Arguments:  existing mailbox name
+               new mailbox name
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - rename completed
+               NO - rename failure: can't rename mailbox with that name,
+                    can't rename to mailbox with that name
+               BAD - command unknown or arguments invalid
+
+      The RENAME command changes the name of a mailbox.  A tagged OK
+      response is returned only if the mailbox has been renamed.  It is
+      an error to attempt to rename from a mailbox name that does not
+      exist or to a mailbox name that already exists.  Any error in
+      renaming will return a tagged NO response.
+
+      If the name has inferior hierarchical names, then the inferior
+      hierarchical names MUST also be renamed.  For example, a rename of
+      "foo" to "zap" will rename "foo/bar" (assuming "/" is the
+      hierarchy delimiter character) to "zap/bar".
+
+      If the server's hierarchy separator character appears in the name,
+      the server SHOULD create any superior hierarchical names that are
+      needed for the RENAME command to complete successfully.  In other
+      words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a
+      server in which "/" is the hierarchy separator character SHOULD
+      create baz/ and baz/rag/ if they do not already exist.
+
+
+
+
+
+Crispin                     Standards Track                    [Page 37]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      The value of the highest-used unique identifier of the old mailbox
+      name MUST be preserved so that a new mailbox created with the same
+      name will not reuse the identifiers of the former incarnation,
+      UNLESS the new incarnation has a different unique identifier
+      validity value.  See the description of the UID command for more
+      detail.
+
+      Renaming INBOX is permitted, and has special behavior.  It moves
+      all messages in INBOX to a new mailbox with the given name,
+      leaving INBOX empty.  If the server implementation supports
+      inferior hierarchical names of INBOX, these are unaffected by a
+      rename of INBOX.
+
+   Examples:   C: A682 LIST "" *
+               S: * LIST () "/" blurdybloop
+               S: * LIST (\Noselect) "/" foo
+               S: * LIST () "/" foo/bar
+               S: A682 OK LIST completed
+               C: A683 RENAME blurdybloop sarasoop
+               S: A683 OK RENAME completed
+               C: A684 RENAME foo zowie
+               S: A684 OK RENAME Completed
+               C: A685 LIST "" *
+               S: * LIST () "/" sarasoop
+               S: * LIST (\Noselect) "/" zowie
+               S: * LIST () "/" zowie/bar
+               S: A685 OK LIST completed
+
+               C: Z432 LIST "" *
+               S: * LIST () "." INBOX
+               S: * LIST () "." INBOX.bar
+               S: Z432 OK LIST completed
+               C: Z433 RENAME INBOX old-mail
+               S: Z433 OK RENAME completed
+               C: Z434 LIST "" *
+               S: * LIST () "." INBOX
+               S: * LIST () "." INBOX.bar
+               S: * LIST () "." old-mail
+               S: Z434 OK LIST completed
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 38]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.3.6.  SUBSCRIBE Command
+
+   Arguments:  mailbox
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - subscribe completed
+               NO - subscribe failure: can't subscribe to that name
+               BAD - command unknown or arguments invalid
+
+      The SUBSCRIBE command adds the specified mailbox name to the
+      server's set of "active" or "subscribed" mailboxes as returned by
+      the LSUB command.  This command returns a tagged OK response only
+      if the subscription is successful.
+
+      A server MAY validate the mailbox argument to SUBSCRIBE to verify
+      that it exists.  However, it MUST NOT unilaterally remove an
+      existing mailbox name from the subscription list even if a mailbox
+      by that name no longer exists.
+
+           Note: This requirement is because a server site can
+           choose to routinely remove a mailbox with a well-known
+           name (e.g., "system-alerts") after its contents expire,
+           with the intention of recreating it when new contents
+           are appropriate.
+
+
+   Example:    C: A002 SUBSCRIBE #news.comp.mail.mime
+               S: A002 OK SUBSCRIBE completed
+
+
+6.3.7.  UNSUBSCRIBE Command
+
+   Arguments:  mailbox name
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - unsubscribe completed
+               NO - unsubscribe failure: can't unsubscribe that name
+               BAD - command unknown or arguments invalid
+
+      The UNSUBSCRIBE command removes the specified mailbox name from
+      the server's set of "active" or "subscribed" mailboxes as returned
+      by the LSUB command.  This command returns a tagged OK response
+      only if the unsubscription is successful.
+
+   Example:    C: A002 UNSUBSCRIBE #news.comp.mail.mime
+               S: A002 OK UNSUBSCRIBE completed
+
+
+
+Crispin                     Standards Track                    [Page 39]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.3.8.  LIST Command
+
+   Arguments:  reference name
+               mailbox name with possible wildcards
+
+   Responses:  untagged responses: LIST
+
+   Result:     OK - list completed
+               NO - list failure: can't list that reference or name
+               BAD - command unknown or arguments invalid
+
+      The LIST command returns a subset of names from the complete set
+      of all names available to the client.  Zero or more untagged LIST
+      replies are returned, containing the name attributes, hierarchy
+      delimiter, and name; see the description of the LIST reply for
+      more detail.
+
+      The LIST command SHOULD return its data quickly, without undue
+      delay.  For example, it SHOULD NOT go to excess trouble to
+      calculate the \Marked or \Unmarked status or perform other
+      processing; if each name requires 1 second of processing, then a
+      list of 1200 names would take 20 minutes!
+
+      An empty ("" string) reference name argument indicates that the
+      mailbox name is interpreted as by SELECT.  The returned mailbox
+      names MUST match the supplied mailbox name pattern.  A non-empty
+      reference name argument is the name of a mailbox or a level of
+      mailbox hierarchy, and indicates the context in which the mailbox
+      name is interpreted.
+
+      An empty ("" string) mailbox name argument is a special request to
+      return the hierarchy delimiter and the root name of the name given
+      in the reference.  The value returned as the root MAY be the empty
+      string if the reference is non-rooted or is an empty string.  In
+      all cases, a hierarchy delimiter (or NIL if there is no hierarchy)
+      is returned.  This permits a client to get the hierarchy delimiter
+      (or find out that the mailbox names are flat) even when no
+      mailboxes by that name currently exist.
+
+      The reference and mailbox name arguments are interpreted into a
+      canonical form that represents an unambiguous left-to-right
+      hierarchy.  The returned mailbox names will be in the interpreted
+      form.
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 40]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+           Note: The interpretation of the reference argument is
+           implementation-defined.  It depends upon whether the
+           server implementation has a concept of the "current
+           working directory" and leading "break out characters",
+           which override the current working directory.
+
+           For example, on a server which exports a UNIX or NT
+           filesystem, the reference argument contains the current
+           working directory, and the mailbox name argument would
+           contain the name as interpreted in the current working
+           directory.
+
+           If a server implementation has no concept of break out
+           characters, the canonical form is normally the reference
+           name appended with the mailbox name.  Note that if the
+           server implements the namespace convention (section
+           5.1.2), "#" is a break out character and must be treated
+           as such.
+
+           If the reference argument is not a level of mailbox
+           hierarchy (that is, it is a \NoInferiors name), and/or
+           the reference argument does not end with the hierarchy
+           delimiter, it is implementation-dependent how this is
+           interpreted.  For example, a reference of "foo/bar" and
+           mailbox name of "rag/baz" could be interpreted as
+           "foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/baz".
+           A client SHOULD NOT use such a reference argument except
+           at the explicit request of the user.  A hierarchical
+           browser MUST NOT make any assumptions about server
+           interpretation of the reference unless the reference is
+           a level of mailbox hierarchy AND ends with the hierarchy
+           delimiter.
+
+      Any part of the reference argument that is included in the
+      interpreted form SHOULD prefix the interpreted form.  It SHOULD
+      also be in the same form as the reference name argument.  This
+      rule permits the client to determine if the returned mailbox name
+      is in the context of the reference argument, or if something about
+      the mailbox argument overrode the reference argument.  Without
+      this rule, the client would have to have knowledge of the server's
+      naming semantics including what characters are "breakouts" that
+      override a naming context.
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 41]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+           For example, here are some examples of how references
+           and mailbox names might be interpreted on a UNIX-based
+           server:
+
+               Reference     Mailbox Name  Interpretation
+               ------------  ------------  --------------
+               ~smith/Mail/  foo.*         ~smith/Mail/foo.*
+               archive/      %             archive/%
+               #news.        comp.mail.*   #news.comp.mail.*
+               ~smith/Mail/  /usr/doc/foo  /usr/doc/foo
+               archive/      ~fred/Mail/*  ~fred/Mail/*
+
+           The first three examples demonstrate interpretations in
+           the context of the reference argument.  Note that
+           "~smith/Mail" SHOULD NOT be transformed into something
+           like "/u2/users/smith/Mail", or it would be impossible
+           for the client to determine that the interpretation was
+           in the context of the reference.
+
+      The character "*" is a wildcard, and matches zero or more
+      characters at this position.  The character "%" is similar to "*",
+      but it does not match a hierarchy delimiter.  If the "%" wildcard
+      is the last character of a mailbox name argument, matching levels
+      of hierarchy are also returned.  If these levels of hierarchy are
+      not also selectable mailboxes, they are returned with the
+      \Noselect mailbox name attribute (see the description of the LIST
+      response for more details).
+
+      Server implementations are permitted to "hide" otherwise
+      accessible mailboxes from the wildcard characters, by preventing
+      certain characters or names from matching a wildcard in certain
+      situations.  For example, a UNIX-based server might restrict the
+      interpretation of "*" so that an initial "/" character does not
+      match.
+
+      The special name INBOX is included in the output from LIST, if
+      INBOX is supported by this server for this user and if the
+      uppercase string "INBOX" matches the interpreted reference and
+      mailbox name arguments with wildcards as described above.  The
+      criteria for omitting INBOX is whether SELECT INBOX will return
+      failure; it is not relevant whether the user's real INBOX resides
+      on this or some other server.
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 42]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   Example:    C: A101 LIST "" ""
+               S: * LIST (\Noselect) "/" ""
+               S: A101 OK LIST Completed
+               C: A102 LIST #news.comp.mail.misc ""
+               S: * LIST (\Noselect) "." #news.
+               S: A102 OK LIST Completed
+               C: A103 LIST /usr/staff/jones ""
+               S: * LIST (\Noselect) "/" /
+               S: A103 OK LIST Completed
+               C: A202 LIST ~/Mail/ %
+               S: * LIST (\Noselect) "/" ~/Mail/foo
+               S: * LIST () "/" ~/Mail/meetings
+               S: A202 OK LIST completed
+
+
+6.3.9.  LSUB Command
+
+   Arguments:  reference name
+               mailbox name with possible wildcards
+
+   Responses:  untagged responses: LSUB
+
+   Result:     OK - lsub completed
+               NO - lsub failure: can't list that reference or name
+               BAD - command unknown or arguments invalid
+
+      The LSUB command returns a subset of names from the set of names
+      that the user has declared as being "active" or "subscribed".
+      Zero or more untagged LSUB replies are returned.  The arguments to
+      LSUB are in the same form as those for LIST.
+
+      The returned untagged LSUB response MAY contain different mailbox
+      flags from a LIST untagged response.  If this should happen, the
+      flags in the untagged LIST are considered more authoritative.
+
+      A special situation occurs when using LSUB with the % wildcard.
+      Consider what happens if "foo/bar" (with a hierarchy delimiter of
+      "/") is subscribed but "foo" is not.  A "%" wildcard to LSUB must
+      return foo, not foo/bar, in the LSUB response, and it MUST be
+      flagged with the \Noselect attribute.
+
+      The server MUST NOT unilaterally remove an existing mailbox name
+      from the subscription list even if a mailbox by that name no
+      longer exists.
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 43]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   Example:    C: A002 LSUB "#news." "comp.mail.*"
+               S: * LSUB () "." #news.comp.mail.mime
+               S: * LSUB () "." #news.comp.mail.misc
+               S: A002 OK LSUB completed
+               C: A003 LSUB "#news." "comp.%"
+               S: * LSUB (\NoSelect) "." #news.comp.mail
+               S: A003 OK LSUB completed
+
+
+6.3.10. STATUS Command
+
+   Arguments:  mailbox name
+               status data item names
+
+   Responses:  untagged responses: STATUS
+
+   Result:     OK - status completed
+               NO - status failure: no status for that name
+               BAD - command unknown or arguments invalid
+
+      The STATUS command requests the status of the indicated mailbox.
+      It does not change the currently selected mailbox, nor does it
+      affect the state of any messages in the queried mailbox (in
+      particular, STATUS MUST NOT cause messages to lose the \Recent
+      flag).
+
+      The STATUS command provides an alternative to opening a second
+      IMAP4rev1 connection and doing an EXAMINE command on a mailbox to
+      query that mailbox's status without deselecting the current
+      mailbox in the first IMAP4rev1 connection.
+
+      Unlike the LIST command, the STATUS command is not guaranteed to
+      be fast in its response.  Under certain circumstances, it can be
+      quite slow.  In some implementations, the server is obliged to
+      open the mailbox read-only internally to obtain certain status
+      information.  Also unlike the LIST command, the STATUS command
+      does not accept wildcards.
+
+           Note: The STATUS command is intended to access the
+           status of mailboxes other than the currently selected
+           mailbox.  Because the STATUS command can cause the
+           mailbox to be opened internally, and because this
+           information is available by other means on the selected
+           mailbox, the STATUS command SHOULD NOT be used on the
+           currently selected mailbox.
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 44]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+           The STATUS command MUST NOT be used as a "check for new
+           messages in the selected mailbox" operation (refer to
+           sections 7, 7.3.1, and 7.3.2 for more information about
+           the proper method for new message checking).
+
+           Because the STATUS command is not guaranteed to be fast
+           in its results, clients SHOULD NOT expect to be able to
+           issue many consecutive STATUS commands and obtain
+           reasonable performance.
+
+      The currently defined status data items that can be requested are:
+
+      MESSAGES
+         The number of messages in the mailbox.
+
+      RECENT
+         The number of messages with the \Recent flag set.
+
+      UIDNEXT
+         The next unique identifier value of the mailbox.  Refer to
+         section 2.3.1.1 for more information.
+
+      UIDVALIDITY
+         The unique identifier validity value of the mailbox.  Refer to
+         section 2.3.1.1 for more information.
+
+      UNSEEN
+         The number of messages which do not have the \Seen flag set.
+
+
+   Example:    C: A042 STATUS blurdybloop (UIDNEXT MESSAGES)
+               S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
+               S: A042 OK STATUS completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 45]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.3.11. APPEND Command
+
+   Arguments:  mailbox name
+               OPTIONAL flag parenthesized list
+               OPTIONAL date/time string
+               message literal
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - append completed
+               NO - append error: can't append to that mailbox, error
+                    in flags or date/time or message text
+               BAD - command unknown or arguments invalid
+
+      The APPEND command appends the literal argument as a new message
+      to the end of the specified destination mailbox.  This argument
+      SHOULD be in the format of an [RFC-2822] message.  8-bit
+      characters are permitted in the message.  A server implementation
+      that is unable to preserve 8-bit data properly MUST be able to
+      reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB]
+      content transfer encoding.
+
+           Note: There MAY be exceptions, e.g., draft messages, in
+           which required [RFC-2822] header lines are omitted in
+           the message literal argument to APPEND.  The full
+           implications of doing so MUST be understood and
+           carefully weighed.
+
+      If a flag parenthesized list is specified, the flags SHOULD be set
+      in the resulting message; otherwise, the flag list of the
+      resulting message is set to empty by default.  In either case, the
+      Recent flag is also set.
+
+      If a date-time is specified, the internal date SHOULD be set in
+      the resulting message; otherwise, the internal date of the
+      resulting message is set to the current date and time by default.
+
+      If the append is unsuccessful for any reason, the mailbox MUST be
+      restored to its state before the APPEND attempt; no partial
+      appending is permitted.
+
+      If the destination mailbox does not exist, a server MUST return an
+      error, and MUST NOT automatically create the mailbox.  Unless it
+      is certain that the destination mailbox can not be created, the
+      server MUST send the response code "[TRYCREATE]" as the prefix of
+      the text of the tagged NO response.  This gives a hint to the
+      client that it can attempt a CREATE command and retry the APPEND
+      if the CREATE is successful.
+
+
+
+Crispin                     Standards Track                    [Page 46]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      If the mailbox is currently selected, the normal new message
+      actions SHOULD occur.  Specifically, the server SHOULD notify the
+      client immediately via an untagged EXISTS response.  If the server
+      does not do so, the client MAY issue a NOOP command (or failing
+      that, a CHECK command) after one or more APPEND commands.
+
+   Example:    C: A003 APPEND saved-messages (\Seen) {310}
+               S: + Ready for literal data
+               C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+               C: From: Fred Foobar <foobar@Blurdybloop.COM>
+               C: Subject: afternoon meeting
+               C: To: mooch@owatagu.siam.edu
+               C: Message-Id: <B27397-0100000@Blurdybloop.COM>
+               C: MIME-Version: 1.0
+               C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+               C:
+               C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+               C:
+               S: A003 OK APPEND completed
+
+        Note: The APPEND command is not used for message delivery,
+        because it does not provide a mechanism to transfer [SMTP]
+        envelope information.
+
+6.4.    Client Commands - Selected State
+
+   In the selected state, commands that manipulate messages in a mailbox
+   are permitted.
+
+   In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+   and the authenticated state commands (SELECT, EXAMINE, CREATE,
+   DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, STATUS, and
+   APPEND), the following commands are valid in the selected state:
+   CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, STORE, COPY, and UID.
+
+6.4.1.  CHECK Command
+
+   Arguments:  none
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - check completed
+               BAD - command unknown or arguments invalid
+
+      The CHECK command requests a checkpoint of the currently selected
+      mailbox.  A checkpoint refers to any implementation-dependent
+      housekeeping associated with the mailbox (e.g., resolving the
+      server's in-memory state of the mailbox with the state on its
+
+
+
+Crispin                     Standards Track                    [Page 47]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      disk) that is not normally executed as part of each command.  A
+      checkpoint MAY take a non-instantaneous amount of real time to
+      complete.  If a server implementation has no such housekeeping
+      considerations, CHECK is equivalent to NOOP.
+
+      There is no guarantee that an EXISTS untagged response will happen
+      as a result of CHECK.  NOOP, not CHECK, SHOULD be used for new
+      message polling.
+
+   Example:    C: FXXZ CHECK
+               S: FXXZ OK CHECK Completed
+
+
+6.4.2.  CLOSE Command
+
+   Arguments:  none
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - close completed, now in authenticated state
+               BAD - command unknown or arguments invalid
+
+      The CLOSE command permanently removes all messages that have the
+      \Deleted flag set from the currently selected mailbox, and returns
+      to the authenticated state from the selected state.  No untagged
+      EXPUNGE responses are sent.
+
+      No messages are removed, and no error is given, if the mailbox is
+      selected by an EXAMINE command or is otherwise selected read-only.
+
+      Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT
+      command MAY be issued without previously issuing a CLOSE command.
+      The SELECT, EXAMINE, and LOGOUT commands implicitly close the
+      currently selected mailbox without doing an expunge.  However,
+      when many messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT
+      sequence is considerably faster than an EXPUNGE-LOGOUT or
+      EXPUNGE-SELECT because no untagged EXPUNGE responses (which the
+      client would probably ignore) are sent.
+
+   Example:    C: A341 CLOSE
+               S: A341 OK CLOSE completed
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 48]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.4.3.  EXPUNGE Command
+
+   Arguments:  none
+
+   Responses:  untagged responses: EXPUNGE
+
+   Result:     OK - expunge completed
+               NO - expunge failure: can't expunge (e.g., permission
+                    denied)
+               BAD - command unknown or arguments invalid
+
+      The EXPUNGE command permanently removes all messages that have the
+      \Deleted flag set from the currently selected mailbox.  Before
+      returning an OK to the client, an untagged EXPUNGE response is
+      sent for each message that is removed.
+
+   Example:    C: A202 EXPUNGE
+               S: * 3 EXPUNGE
+               S: * 3 EXPUNGE
+               S: * 5 EXPUNGE
+               S: * 8 EXPUNGE
+               S: A202 OK EXPUNGE completed
+
+        Note: In this example, messages 3, 4, 7, and 11 had the
+        \Deleted flag set.  See the description of the EXPUNGE
+        response for further explanation.
+
+
+6.4.4.  SEARCH Command
+
+   Arguments:  OPTIONAL [CHARSET] specification
+               searching criteria (one or more)
+
+   Responses:  REQUIRED untagged response: SEARCH
+
+   Result:     OK - search completed
+               NO - search error: can't search that [CHARSET] or
+                    criteria
+               BAD - command unknown or arguments invalid
+
+      The SEARCH command searches the mailbox for messages that match
+      the given searching criteria.  Searching criteria consist of one
+      or more search keys.  The untagged SEARCH response from the server
+      contains a listing of message sequence numbers corresponding to
+      those messages that match the searching criteria.
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 49]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      When multiple keys are specified, the result is the intersection
+      (AND function) of all the messages that match those keys.  For
+      example, the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers
+      to all deleted messages from Smith that were placed in the mailbox
+      since February 1, 1994.  A search key can also be a parenthesized
+      list of one or more search keys (e.g., for use with the OR and NOT
+      keys).
+
+      Server implementations MAY exclude [MIME-IMB] body parts with
+      terminal content media types other than TEXT and MESSAGE from
+      consideration in SEARCH matching.
+
+      The OPTIONAL [CHARSET] specification consists of the word
+      "CHARSET" followed by a registered [CHARSET].  It indicates the
+      [CHARSET] of the strings that appear in the search criteria.
+      [MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in
+      [RFC-2822]/[MIME-IMB] headers, MUST be decoded before comparing
+      text in a [CHARSET] other than US-ASCII.  US-ASCII MUST be
+      supported; other [CHARSET]s MAY be supported.
+
+      If the server does not support the specified [CHARSET], it MUST
+      return a tagged NO response (not a BAD).  This response SHOULD
+      contain the BADCHARSET response code, which MAY list the
+      [CHARSET]s supported by the server.
+
+      In all search keys that use strings, a message matches the key if
+      the string is a substring of the field.  The matching is
+      case-insensitive.
+
+      The defined search keys are as follows.  Refer to the Formal
+      Syntax section for the precise syntactic definitions of the
+      arguments.
+
+      <sequence set>
+         Messages with message sequence numbers corresponding to the
+         specified message sequence number set.
+
+      ALL
+         All messages in the mailbox; the default initial key for
+         ANDing.
+
+      ANSWERED
+         Messages with the \Answered flag set.
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 50]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      BCC <string>
+         Messages that contain the specified string in the envelope
+         structure's BCC field.
+
+      BEFORE <date>
+         Messages whose internal date (disregarding time and timezone)
+         is earlier than the specified date.
+
+      BODY <string>
+         Messages that contain the specified string in the body of the
+         message.
+
+      CC <string>
+         Messages that contain the specified string in the envelope
+         structure's CC field.
+
+      DELETED
+         Messages with the \Deleted flag set.
+
+      DRAFT
+         Messages with the \Draft flag set.
+
+      FLAGGED
+         Messages with the \Flagged flag set.
+
+      FROM <string>
+         Messages that contain the specified string in the envelope
+         structure's FROM field.
+
+      HEADER <field-name> <string>
+         Messages that have a header with the specified field-name (as
+         defined in [RFC-2822]) and that contains the specified string
+         in the text of the header (what comes after the colon).  If the
+         string to search is zero-length, this matches all messages that
+         have a header line with the specified field-name regardless of
+         the contents.
+
+      KEYWORD <flag>
+         Messages with the specified keyword flag set.
+
+      LARGER <n>
+         Messages with an [RFC-2822] size larger than the specified
+         number of octets.
+
+      NEW
+         Messages that have the \Recent flag set but not the \Seen flag.
+         This is functionally equivalent to "(RECENT UNSEEN)".
+
+
+
+
+Crispin                     Standards Track                    [Page 51]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      NOT <search-key>
+         Messages that do not match the specified search key.
+
+      OLD
+         Messages that do not have the \Recent flag set.  This is
+         functionally equivalent to "NOT RECENT" (as opposed to "NOT
+         NEW").
+
+      ON <date>
+         Messages whose internal date (disregarding time and timezone)
+         is within the specified date.
+
+      OR <search-key1> <search-key2>
+         Messages that match either search key.
+
+      RECENT
+         Messages that have the \Recent flag set.
+
+      SEEN
+         Messages that have the \Seen flag set.
+
+      SENTBEFORE <date>
+         Messages whose [RFC-2822] Date: header (disregarding time and
+         timezone) is earlier than the specified date.
+
+      SENTON <date>
+         Messages whose [RFC-2822] Date: header (disregarding time and
+         timezone) is within the specified date.
+
+      SENTSINCE <date>
+         Messages whose [RFC-2822] Date: header (disregarding time and
+         timezone) is within or later than the specified date.
+
+      SINCE <date>
+         Messages whose internal date (disregarding time and timezone)
+         is within or later than the specified date.
+
+      SMALLER <n>
+         Messages with an [RFC-2822] size smaller than the specified
+         number of octets.
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 52]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      SUBJECT <string>
+         Messages that contain the specified string in the envelope
+         structure's SUBJECT field.
+
+      TEXT <string>
+         Messages that contain the specified string in the header or
+         body of the message.
+
+      TO <string>
+         Messages that contain the specified string in the envelope
+         structure's TO field.
+
+      UID <sequence set>
+         Messages with unique identifiers corresponding to the specified
+         unique identifier set.  Sequence set ranges are permitted.
+
+      UNANSWERED
+         Messages that do not have the \Answered flag set.
+
+      UNDELETED
+         Messages that do not have the \Deleted flag set.
+
+      UNDRAFT
+         Messages that do not have the \Draft flag set.
+
+      UNFLAGGED
+         Messages that do not have the \Flagged flag set.
+
+      UNKEYWORD <flag>
+         Messages that do not have the specified keyword flag set.
+
+      UNSEEN
+         Messages that do not have the \Seen flag set.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 53]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   Example:    C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith"
+               S: * SEARCH 2 84 882
+               S: A282 OK SEARCH completed
+               C: A283 SEARCH TEXT "string not in mailbox"
+               S: * SEARCH
+               S: A283 OK SEARCH completed
+               C: A284 SEARCH CHARSET UTF-8 TEXT {6}
+               C: XXXXXX
+               S: * SEARCH 43
+               S: A284 OK SEARCH completed
+
+        Note: Since this document is restricted to 7-bit ASCII
+        text, it is not possible to show actual UTF-8 data.  The
+        "XXXXXX" is a placeholder for what would be 6 octets of
+        8-bit data in an actual transaction.
+
+
+6.4.5.  FETCH Command
+
+   Arguments:  sequence set
+               message data item names or macro
+
+   Responses:  untagged responses: FETCH
+
+   Result:     OK - fetch completed
+               NO - fetch error: can't fetch that data
+               BAD - command unknown or arguments invalid
+
+      The FETCH command retrieves data associated with a message in the
+      mailbox.  The data items to be fetched can be either a single atom
+      or a parenthesized list.
+
+      Most data items, identified in the formal syntax under the
+      msg-att-static rule, are static and MUST NOT change for any
+      particular message.  Other data items, identified in the formal
+      syntax under the msg-att-dynamic rule, MAY change, either as a
+      result of a STORE command or due to external events.
+
+           For example, if a client receives an ENVELOPE for a
+           message when it already knows the envelope, it can
+           safely ignore the newly transmitted envelope.
+
+      There are three macros which specify commonly-used sets of data
+      items, and can be used instead of data items.  A macro must be
+      used by itself, and not in conjunction with other macros or data
+      items.
+
+
+
+
+
+Crispin                     Standards Track                    [Page 54]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      ALL
+         Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE)
+
+      FAST
+         Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE)
+
+      FULL
+         Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE
+         BODY)
+
+      The currently defined data items that can be fetched are:
+
+      BODY
+         Non-extensible form of BODYSTRUCTURE.
+
+      BODY[<section>]<<partial>>
+         The text of a particular body section.  The section
+         specification is a set of zero or more part specifiers
+         delimited by periods.  A part specifier is either a part number
+         or one of the following: HEADER, HEADER.FIELDS,
+         HEADER.FIELDS.NOT, MIME, and TEXT.  An empty section
+         specification refers to the entire message, including the
+         header.
+
+         Every message has at least one part number.  Non-[MIME-IMB]
+         messages, and non-multipart [MIME-IMB] messages with no
+         encapsulated message, only have a part 1.
+
+         Multipart messages are assigned consecutive part numbers, as
+         they occur in the message.  If a particular part is of type
+         message or multipart, its parts MUST be indicated by a period
+         followed by the part number within that nested multipart part.
+
+         A part of type MESSAGE/RFC822 also has nested part numbers,
+         referring to parts of the MESSAGE part's body.
+
+         The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and TEXT part
+         specifiers can be the sole part specifier or can be prefixed by
+         one or more numeric part specifiers, provided that the numeric
+         part specifier refers to a part of type MESSAGE/RFC822.  The
+         MIME part specifier MUST be prefixed by one or more numeric
+         part specifiers.
+
+         The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part
+         specifiers refer to the [RFC-2822] header of the message or of
+         an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
+         HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
+         field-name (as defined in [RFC-2822]) names, and return a
+
+
+
+Crispin                     Standards Track                    [Page 55]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+         subset of the header.  The subset returned by HEADER.FIELDS
+         contains only those header fields with a field-name that
+         matches one of the names in the list; similarly, the subset
+         returned by HEADER.FIELDS.NOT contains only the header fields
+         with a non-matching field-name.  The field-matching is
+         case-insensitive but otherwise exact.  Subsetting does not
+         exclude the [RFC-2822] delimiting blank line between the header
+         and the body; the blank line is included in all header fetches,
+         except in the case of a message which has no body and no blank
+         line.
+
+         The MIME part specifier refers to the [MIME-IMB] header for
+         this part.
+
+         The TEXT part specifier refers to the text body of the message,
+         omitting the [RFC-2822] header.
+
+            Here is an example of a complex message with some of its
+            part specifiers:
+
+       HEADER     ([RFC-2822] header of the message)
+       TEXT       ([RFC-2822] text body of the message) MULTIPART/MIXED
+       1          TEXT/PLAIN
+       2          APPLICATION/OCTET-STREAM
+       3          MESSAGE/RFC822
+       3.HEADER   ([RFC-2822] header of the message)
+       3.TEXT     ([RFC-2822] text body of the message) MULTIPART/MIXED
+       3.1        TEXT/PLAIN
+       3.2        APPLICATION/OCTET-STREAM
+       4          MULTIPART/MIXED
+       4.1        IMAGE/GIF
+       4.1.MIME   ([MIME-IMB] header for the IMAGE/GIF)
+       4.2        MESSAGE/RFC822
+       4.2.HEADER ([RFC-2822] header of the message)
+       4.2.TEXT   ([RFC-2822] text body of the message) MULTIPART/MIXED
+       4.2.1      TEXT/PLAIN
+       4.2.2      MULTIPART/ALTERNATIVE
+       4.2.2.1    TEXT/PLAIN
+       4.2.2.2    TEXT/RICHTEXT
+
+
+         It is possible to fetch a substring of the designated text.
+         This is done by appending an open angle bracket ("<"), the
+         octet position of the first desired octet, a period, the
+         maximum number of octets desired, and a close angle bracket
+         (">") to the part specifier.  If the starting octet is beyond
+         the end of the text, an empty string is returned.
+
+
+
+
+Crispin                     Standards Track                    [Page 56]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+         Any partial fetch that attempts to read beyond the end of the
+         text is truncated as appropriate.  A partial fetch that starts
+         at octet 0 is returned as a partial fetch, even if this
+         truncation happened.
+
+            Note: This means that BODY[]<0.2048> of a 1500-octet message
+            will return BODY[]<0> with a literal of size 1500, not
+            BODY[].
+
+            Note: A substring fetch of a HEADER.FIELDS or
+            HEADER.FIELDS.NOT part specifier is calculated after
+            subsetting the header.
+
+         The \Seen flag is implicitly set; if this causes the flags to
+         change, they SHOULD be included as part of the FETCH responses.
+
+      BODY.PEEK[<section>]<<partial>>
+         An alternate form of BODY[<section>] that does not implicitly
+         set the \Seen flag.
+
+      BODYSTRUCTURE
+         The [MIME-IMB] body structure of the message.  This is computed
+         by the server by parsing the [MIME-IMB] header fields in the
+         [RFC-2822] header and [MIME-IMB] headers.
+
+      ENVELOPE
+         The envelope structure of the message.  This is computed by the
+         server by parsing the [RFC-2822] header into the component
+         parts, defaulting various fields as necessary.
+
+      FLAGS
+         The flags that are set for this message.
+
+      INTERNALDATE
+         The internal date of the message.
+
+      RFC822
+         Functionally equivalent to BODY[], differing in the syntax of
+         the resulting untagged FETCH data (RFC822 is returned).
+
+      RFC822.HEADER
+         Functionally equivalent to BODY.PEEK[HEADER], differing in the
+         syntax of the resulting untagged FETCH data (RFC822.HEADER is
+         returned).
+
+      RFC822.SIZE
+         The [RFC-2822] size of the message.
+
+
+
+
+Crispin                     Standards Track                    [Page 57]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      RFC822.TEXT
+         Functionally equivalent to BODY[TEXT], differing in the syntax
+         of the resulting untagged FETCH data (RFC822.TEXT is returned).
+
+      UID
+         The unique identifier for the message.
+
+
+   Example:    C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
+               S: * 2 FETCH ....
+               S: * 3 FETCH ....
+               S: * 4 FETCH ....
+               S: A654 OK FETCH completed
+
+
+6.4.6.  STORE Command
+
+   Arguments:  sequence set
+               message data item name
+               value for message data item
+
+   Responses:  untagged responses: FETCH
+
+   Result:     OK - store completed
+               NO - store error: can't store that data
+               BAD - command unknown or arguments invalid
+
+      The STORE command alters data associated with a message in the
+      mailbox.  Normally, STORE will return the updated value of the
+      data with an untagged FETCH response.  A suffix of ".SILENT" in
+      the data item name prevents the untagged FETCH, and the server
+      SHOULD assume that the client has determined the updated value
+      itself or does not care about the updated value.
+
+           Note: Regardless of whether or not the ".SILENT" suffix
+           was used, the server SHOULD send an untagged FETCH
+           response if a change to a message's flags from an
+           external source is observed.  The intent is that the
+           status of the flags is determinate without a race
+           condition.
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 58]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      The currently defined data items that can be stored are:
+
+      FLAGS <flag list>
+         Replace the flags for the message (other than \Recent) with the
+         argument.  The new value of the flags is returned as if a FETCH
+         of those flags was done.
+
+      FLAGS.SILENT <flag list>
+         Equivalent to FLAGS, but without returning a new value.
+
+      +FLAGS <flag list>
+         Add the argument to the flags for the message.  The new value
+         of the flags is returned as if a FETCH of those flags was done.
+
+      +FLAGS.SILENT <flag list>
+         Equivalent to +FLAGS, but without returning a new value.
+
+      -FLAGS <flag list>
+         Remove the argument from the flags for the message.  The new
+         value of the flags is returned as if a FETCH of those flags was
+         done.
+
+      -FLAGS.SILENT <flag list>
+         Equivalent to -FLAGS, but without returning a new value.
+
+
+   Example:    C: A003 STORE 2:4 +FLAGS (\Deleted)
+               S: * 2 FETCH (FLAGS (\Deleted \Seen))
+               S: * 3 FETCH (FLAGS (\Deleted))
+               S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen))
+               S: A003 OK STORE completed
+
+
+6.4.7.  COPY Command
+
+   Arguments:  sequence set
+               mailbox name
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - copy completed
+               NO - copy error: can't copy those messages or to that
+                    name
+               BAD - command unknown or arguments invalid
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 59]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      The COPY command copies the specified message(s) to the end of the
+      specified destination mailbox.  The flags and internal date of the
+      message(s) SHOULD be preserved, and the Recent flag SHOULD be set,
+      in the copy.
+
+      If the destination mailbox does not exist, a server SHOULD return
+      an error.  It SHOULD NOT automatically create the mailbox.  Unless
+      it is certain that the destination mailbox can not be created, the
+      server MUST send the response code "[TRYCREATE]" as the prefix of
+      the text of the tagged NO response.  This gives a hint to the
+      client that it can attempt a CREATE command and retry the COPY if
+      the CREATE is successful.
+
+      If the COPY command is unsuccessful for any reason, server
+      implementations MUST restore the destination mailbox to its state
+      before the COPY attempt.
+
+   Example:    C: A003 COPY 2:4 MEETING
+               S: A003 OK COPY completed
+
+
+6.4.8.  UID Command
+
+   Arguments:  command name
+               command arguments
+
+   Responses:  untagged responses: FETCH, SEARCH
+
+   Result:     OK - UID command completed
+               NO - UID command error
+               BAD - command unknown or arguments invalid
+
+      The UID command has two forms.  In the first form, it takes as its
+      arguments a COPY, FETCH, or STORE command with arguments
+      appropriate for the associated command.  However, the numbers in
+      the sequence set argument are unique identifiers instead of
+      message sequence numbers.  Sequence set ranges are permitted, but
+      there is no guarantee that unique identifiers will be contiguous.
+
+      A non-existent unique identifier is ignored without any error
+      message generated.  Thus, it is possible for a UID FETCH command
+      to return an OK without any data or a UID COPY or UID STORE to
+      return an OK without performing any operations.
+
+      In the second form, the UID command takes a SEARCH command with
+      SEARCH command arguments.  The interpretation of the arguments is
+      the same as with SEARCH; however, the numbers returned in a SEARCH
+      response for a UID SEARCH command are unique identifiers instead
+
+
+
+Crispin                     Standards Track                    [Page 60]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      of message sequence numbers.  For example, the command UID SEARCH
+      1:100 UID 443:557 returns the unique identifiers corresponding to
+      the intersection of two sequence sets, the message sequence number
+      range 1:100 and the UID range 443:557.
+
+           Note: in the above example, the UID range 443:557
+           appears.  The same comment about a non-existent unique
+           identifier being ignored without any error message also
+           applies here.  Hence, even if neither UID 443 or 557
+           exist, this range is valid and would include an existing
+           UID 495.
+
+           Also note that a UID range of 559:* always includes the
+           UID of the last message in the mailbox, even if 559 is
+           higher than any assigned UID value.  This is because the
+           contents of a range are independent of the order of the
+           range endpoints.  Thus, any UID range with * as one of
+           the endpoints indicates at least one message (the
+           message with the highest numbered UID), unless the
+           mailbox is empty.
+
+      The number after the "*" in an untagged FETCH response is always a
+      message sequence number, not a unique identifier, even for a UID
+      command response.  However, server implementations MUST implicitly
+      include the UID message data item as part of any FETCH response
+      caused by a UID command, regardless of whether a UID was specified
+      as a message data item to the FETCH.
+
+
+      Note: The rule about including the UID message data item as part
+      of a FETCH response primarily applies to the UID FETCH and UID
+      STORE commands, including a UID FETCH command that does not
+      include UID as a message data item.  Although it is unlikely that
+      the other UID commands will cause an untagged FETCH, this rule
+      applies to these commands as well.
+
+   Example:    C: A999 UID FETCH 4827313:4828442 FLAGS
+               S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
+               S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
+               S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
+               S: A999 OK UID FETCH completed
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 61]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+6.5.    Client Commands - Experimental/Expansion
+
+
+6.5.1.  X<atom> Command
+
+   Arguments:  implementation defined
+
+   Responses:  implementation defined
+
+   Result:     OK - command completed
+               NO - failure
+               BAD - command unknown or arguments invalid
+
+      Any command prefixed with an X is an experimental command.
+      Commands which are not part of this specification, a standard or
+      standards-track revision of this specification, or an
+      IESG-approved experimental protocol, MUST use the X prefix.
+
+      Any added untagged responses issued by an experimental command
+      MUST also be prefixed with an X.  Server implementations MUST NOT
+      send any such untagged responses, unless the client requested it
+      by issuing the associated experimental command.
+
+   Example:    C: a441 CAPABILITY
+               S: * CAPABILITY IMAP4rev1 XPIG-LATIN
+               S: a441 OK CAPABILITY completed
+               C: A442 XPIG-LATIN
+               S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
+               S: A442 OK XPIG-LATIN ompleted-cay
+
+7.      Server Responses
+
+   Server responses are in three forms: status responses, server data,
+   and command continuation request.  The information contained in a
+   server response, identified by "Contents:" in the response
+   descriptions below, is described by function, not by syntax.  The
+   precise syntax of server responses is described in the Formal Syntax
+   section.
+
+   The client MUST be prepared to accept any response at all times.
+
+   Status responses can be tagged or untagged.  Tagged status responses
+   indicate the completion result (OK, NO, or BAD status) of a client
+   command, and have a tag matching the command.
+
+   Some status responses, and all server data, are untagged.  An
+   untagged response is indicated by the token "*" instead of a tag.
+   Untagged status responses indicate server greeting, or server status
+
+
+
+Crispin                     Standards Track                    [Page 62]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   that does not indicate the completion of a command (for example, an
+   impending system shutdown alert).  For historical reasons, untagged
+   server data responses are also called "unsolicited data", although
+   strictly speaking, only unilateral server data is truly
+   "unsolicited".
+
+   Certain server data MUST be recorded by the client when it is
+   received; this is noted in the description of that data.  Such data
+   conveys critical information which affects the interpretation of all
+   subsequent commands and responses (e.g., updates reflecting the
+   creation or destruction of messages).
+
+   Other server data SHOULD be recorded for later reference; if the
+   client does not need to record the data, or if recording the data has
+   no obvious purpose (e.g., a SEARCH response when no SEARCH command is
+   in progress), the data SHOULD be ignored.
+
+   An example of unilateral untagged server data occurs when the IMAP
+   connection is in the selected state.  In the selected state, the
+   server checks the mailbox for new messages as part of command
+   execution.  Normally, this is part of the execution of every command;
+   hence, a NOOP command suffices to check for new messages.  If new
+   messages are found, the server sends untagged EXISTS and RECENT
+   responses reflecting the new size of the mailbox.  Server
+   implementations that offer multiple simultaneous access to the same
+   mailbox SHOULD also send appropriate unilateral untagged FETCH and
+   EXPUNGE responses if another agent changes the state of any message
+   flags or expunges any messages.
+
+   Command continuation request responses use the token "+" instead of a
+   tag.  These responses are sent by the server to indicate acceptance
+   of an incomplete client command and readiness for the remainder of
+   the command.
+
+7.1.    Server Responses - Status Responses
+
+   Status responses are OK, NO, BAD, PREAUTH and BYE.  OK, NO, and BAD
+   can be tagged or untagged.  PREAUTH and BYE are always untagged.
+
+   Status responses MAY include an OPTIONAL "response code".  A response
+   code consists of data inside square brackets in the form of an atom,
+   possibly followed by a space and arguments.  The response code
+   contains additional information or status codes for client software
+   beyond the OK/NO/BAD condition, and are defined when there is a
+   specific action that a client can take based upon the additional
+   information.
+
+
+
+
+
+Crispin                     Standards Track                    [Page 63]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   The currently defined response codes are:
+
+      ALERT
+
+         The human-readable text contains a special alert that MUST be
+         presented to the user in a fashion that calls the user's
+         attention to the message.
+
+      BADCHARSET
+
+         Optionally followed by a parenthesized list of charsets.  A
+         SEARCH failed because the given charset is not supported by
+         this implementation.  If the optional list of charsets is
+         given, this lists the charsets that are supported by this
+         implementation.
+
+      CAPABILITY
+
+         Followed by a list of capabilities.  This can appear in the
+         initial OK or PREAUTH response to transmit an initial
+         capabilities list.  This makes it unnecessary for a client to
+         send a separate CAPABILITY command if it recognizes this
+         response.
+
+      PARSE
+
+         The human-readable text represents an error in parsing the
+         [RFC-2822] header or [MIME-IMB] headers of a message in the
+         mailbox.
+
+      PERMANENTFLAGS
+
+         Followed by a parenthesized list of flags, indicates which of
+         the known flags the client can change permanently.  Any flags
+         that are in the FLAGS untagged response, but not the
+         PERMANENTFLAGS list, can not be set permanently.  If the client
+         attempts to STORE a flag that is not in the PERMANENTFLAGS
+         list, the server will either ignore the change or store the
+         state change for the remainder of the current session only.
+         The PERMANENTFLAGS list can also include the special flag \*,
+         which indicates that it is possible to create new keywords by
+         attempting to store those flags in the mailbox.
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 64]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      READ-ONLY
+
+         The mailbox is selected read-only, or its access while selected
+         has changed from read-write to read-only.
+
+      READ-WRITE
+
+         The mailbox is selected read-write, or its access while
+         selected has changed from read-only to read-write.
+
+      TRYCREATE
+
+         An APPEND or COPY attempt is failing because the target mailbox
+         does not exist (as opposed to some other reason).  This is a
+         hint to the client that the operation can succeed if the
+         mailbox is first created by the CREATE command.
+
+      UIDNEXT
+
+         Followed by a decimal number, indicates the next unique
+         identifier value.  Refer to section 2.3.1.1 for more
+         information.
+
+      UIDVALIDITY
+
+         Followed by a decimal number, indicates the unique identifier
+         validity value.  Refer to section 2.3.1.1 for more information.
+
+      UNSEEN
+
+         Followed by a decimal number, indicates the number of the first
+         message without the \Seen flag set.
+
+      Additional response codes defined by particular client or server
+      implementations SHOULD be prefixed with an "X" until they are
+      added to a revision of this protocol.  Client implementations
+      SHOULD ignore response codes that they do not recognize.
+
+7.1.1.  OK Response
+
+   Contents:   OPTIONAL response code
+               human-readable text
+
+      The OK response indicates an information message from the server.
+      When tagged, it indicates successful completion of the associated
+      command.  The human-readable text MAY be presented to the user as
+      an information message.  The untagged form indicates an
+
+
+
+
+Crispin                     Standards Track                    [Page 65]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      information-only message; the nature of the information MAY be
+      indicated by a response code.
+
+      The untagged form is also used as one of three possible greetings
+      at connection startup.  It indicates that the connection is not
+      yet authenticated and that a LOGIN command is needed.
+
+   Example:    S: * OK IMAP4rev1 server ready
+               C: A001 LOGIN fred blurdybloop
+               S: * OK [ALERT] System shutdown in 10 minutes
+               S: A001 OK LOGIN Completed
+
+
+7.1.2.  NO Response
+
+   Contents:   OPTIONAL response code
+               human-readable text
+
+      The NO response indicates an operational error message from the
+      server.  When tagged, it indicates unsuccessful completion of the
+      associated command.  The untagged form indicates a warning; the
+      command can still complete successfully.  The human-readable text
+      describes the condition.
+
+   Example:    C: A222 COPY 1:2 owatagusiam
+               S: * NO Disk is 98% full, please delete unnecessary data
+               S: A222 OK COPY completed
+               C: A223 COPY 3:200 blurdybloop
+               S: * NO Disk is 98% full, please delete unnecessary data
+               S: * NO Disk is 99% full, please delete unnecessary data
+               S: A223 NO COPY failed: disk is full
+
+
+7.1.3.  BAD Response
+
+   Contents:   OPTIONAL response code
+               human-readable text
+
+      The BAD response indicates an error message from the server.  When
+      tagged, it reports a protocol-level error in the client's command;
+      the tag indicates the command that caused the error.  The untagged
+      form indicates a protocol-level error for which the associated
+      command can not be determined; it can also indicate an internal
+      server failure.  The human-readable text describes the condition.
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 66]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   Example:    C: ...very long command line...
+               S: * BAD Command line too long
+               C: ...empty line...
+               S: * BAD Empty command line
+               C: A443 EXPUNGE
+               S: * BAD Disk crash, attempting salvage to a new disk!
+               S: * OK Salvage successful, no data lost
+               S: A443 OK Expunge completed
+
+
+7.1.4.  PREAUTH Response
+
+   Contents:   OPTIONAL response code
+               human-readable text
+
+      The PREAUTH response is always untagged, and is one of three
+      possible greetings at connection startup.  It indicates that the
+      connection has already been authenticated by external means; thus
+      no LOGIN command is needed.
+
+   Example:    S: * PREAUTH IMAP4rev1 server logged in as Smith
+
+
+7.1.5.  BYE Response
+
+   Contents:   OPTIONAL response code
+               human-readable text
+
+      The BYE response is always untagged, and indicates that the server
+      is about to close the connection.  The human-readable text MAY be
+      displayed to the user in a status report by the client.  The BYE
+      response is sent under one of four conditions:
+
+         1) as part of a normal logout sequence.  The server will close
+            the connection after sending the tagged OK response to the
+            LOGOUT command.
+
+         2) as a panic shutdown announcement.  The server closes the
+            connection immediately.
+
+         3) as an announcement of an inactivity autologout.  The server
+            closes the connection immediately.
+
+         4) as one of three possible greetings at connection startup,
+            indicating that the server is not willing to accept a
+            connection from this client.  The server closes the
+            connection immediately.
+
+
+
+
+Crispin                     Standards Track                    [Page 67]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      The difference between a BYE that occurs as part of a normal
+      LOGOUT sequence (the first case) and a BYE that occurs because of
+      a failure (the other three cases) is that the connection closes
+      immediately in the failure case.  In all cases the client SHOULD
+      continue to read response data from the server until the
+      connection is closed; this will ensure that any pending untagged
+      or completion responses are read and processed.
+
+   Example:    S: * BYE Autologout; idle for too long
+
+7.2.    Server Responses - Server and Mailbox Status
+
+   These responses are always untagged.  This is how server and mailbox
+   status data are transmitted from the server to the client.  Many of
+   these responses typically result from a command with the same name.
+
+7.2.1.  CAPABILITY Response
+
+   Contents:   capability listing
+
+      The CAPABILITY response occurs as a result of a CAPABILITY
+      command.  The capability listing contains a space-separated
+      listing of capability names that the server supports.  The
+      capability listing MUST include the atom "IMAP4rev1".
+
+      In addition, client and server implementations MUST implement the
+      STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
+      capabilities.  See the Security Considerations section for
+      important information.
+
+      A capability name which begins with "AUTH=" indicates that the
+      server supports that particular authentication mechanism.
+
+      The LOGINDISABLED capability indicates that the LOGIN command is
+      disabled, and that the server will respond with a tagged NO
+      response to any attempt to use the LOGIN command even if the user
+      name and password are valid.  An IMAP client MUST NOT issue the
+      LOGIN command if the server advertises the LOGINDISABLED
+      capability.
+
+      Other capability names indicate that the server supports an
+      extension, revision, or amendment to the IMAP4rev1 protocol.
+      Server responses MUST conform to this document until the client
+      issues a command that uses the associated capability.
+
+      Capability names MUST either begin with "X" or be standard or
+      standards-track IMAP4rev1 extensions, revisions, or amendments
+      registered with IANA.  A server MUST NOT offer unregistered or
+
+
+
+Crispin                     Standards Track                    [Page 68]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      non-standard capability names, unless such names are prefixed with
+      an "X".
+
+      Client implementations SHOULD NOT require any capability name
+      other than "IMAP4rev1", and MUST ignore any unknown capability
+      names.
+
+      A server MAY send capabilities automatically, by using the
+      CAPABILITY response code in the initial PREAUTH or OK responses,
+      and by sending an updated CAPABILITY response code in the tagged
+      OK response as part of a successful authentication.  It is
+      unnecessary for a client to send a separate CAPABILITY command if
+      it recognizes these automatic capabilities.
+
+   Example:    S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI XPIG-LATIN
+
+
+7.2.2.  LIST Response
+
+   Contents:   name attributes
+               hierarchy delimiter
+               name
+
+      The LIST response occurs as a result of a LIST command.  It
+      returns a single name that matches the LIST specification.  There
+      can be multiple LIST responses for a single LIST command.
+
+      Four name attributes are defined:
+
+      \Noinferiors
+         It is not possible for any child levels of hierarchy to exist
+         under this name; no child levels exist now and none can be
+         created in the future.
+
+      \Noselect
+         It is not possible to use this name as a selectable mailbox.
+
+      \Marked
+         The mailbox has been marked "interesting" by the server; the
+         mailbox probably contains messages that have been added since
+         the last time the mailbox was selected.
+
+      \Unmarked
+         The mailbox does not contain any additional messages since the
+         last time the mailbox was selected.
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 69]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      If it is not feasible for the server to determine whether or not
+      the mailbox is "interesting", or if the name is a \Noselect name,
+      the server SHOULD NOT send either \Marked or \Unmarked.
+
+      The hierarchy delimiter is a character used to delimit levels of
+      hierarchy in a mailbox name.  A client can use it to create child
+      mailboxes, and to search higher or lower levels of naming
+      hierarchy.  All children of a top-level hierarchy node MUST use
+      the same separator character.  A NIL hierarchy delimiter means
+      that no hierarchy exists; the name is a "flat" name.
+
+      The name represents an unambiguous left-to-right hierarchy, and
+      MUST be valid for use as a reference in LIST and LSUB commands.
+      Unless \Noselect is indicated, the name MUST also be valid as an
+      argument for commands, such as SELECT, that accept mailbox names.
+
+   Example:    S: * LIST (\Noselect) "/" ~/Mail/foo
+
+
+7.2.3.  LSUB Response
+
+   Contents:   name attributes
+               hierarchy delimiter
+               name
+
+      The LSUB response occurs as a result of an LSUB command.  It
+      returns a single name that matches the LSUB specification.  There
+      can be multiple LSUB responses for a single LSUB command.  The
+      data is identical in format to the LIST response.
+
+   Example:    S: * LSUB () "." #news.comp.mail.misc
+
+
+7.2.4   STATUS Response
+
+   Contents:   name
+               status parenthesized list
+
+      The STATUS response occurs as a result of an STATUS command.  It
+      returns the mailbox name that matches the STATUS specification and
+      the requested mailbox status information.
+
+   Example:    S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 70]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+7.2.5.  SEARCH Response
+
+   Contents:   zero or more numbers
+
+      The SEARCH response occurs as a result of a SEARCH or UID SEARCH
+      command.  The number(s) refer to those messages that match the
+      search criteria.  For SEARCH, these are message sequence numbers;
+      for UID SEARCH, these are unique identifiers.  Each number is
+      delimited by a space.
+
+   Example:    S: * SEARCH 2 3 6
+
+
+7.2.6.  FLAGS Response
+
+   Contents:   flag parenthesized list
+
+      The FLAGS response occurs as a result of a SELECT or EXAMINE
+      command.  The flag parenthesized list identifies the flags (at a
+      minimum, the system-defined flags) that are applicable for this
+      mailbox.  Flags other than the system flags can also exist,
+      depending on server implementation.
+
+      The update from the FLAGS response MUST be recorded by the client.
+
+   Example:    S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+
+
+7.3.    Server Responses - Mailbox Size
+
+   These responses are always untagged.  This is how changes in the size
+   of the mailbox are transmitted from the server to the client.
+   Immediately following the "*" token is a number that represents a
+   message count.
+
+7.3.1.  EXISTS Response
+
+   Contents:   none
+
+      The EXISTS response reports the number of messages in the mailbox.
+      This response occurs as a result of a SELECT or EXAMINE command,
+      and if the size of the mailbox changes (e.g., new messages).
+
+      The update from the EXISTS response MUST be recorded by the
+      client.
+
+   Example:    S: * 23 EXISTS
+
+
+
+
+Crispin                     Standards Track                    [Page 71]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+7.3.2.  RECENT Response
+
+   Contents:   none
+
+      The RECENT response reports the number of messages with the
+      \Recent flag set.  This response occurs as a result of a SELECT or
+      EXAMINE command, and if the size of the mailbox changes (e.g., new
+      messages).
+
+           Note: It is not guaranteed that the message sequence
+           numbers of recent messages will be a contiguous range of
+           the highest n messages in the mailbox (where n is the
+           value reported by the RECENT response).  Examples of
+           situations in which this is not the case are: multiple
+           clients having the same mailbox open (the first session
+           to be notified will see it as recent, others will
+           probably see it as non-recent), and when the mailbox is
+           re-ordered by a non-IMAP agent.
+
+           The only reliable way to identify recent messages is to
+           look at message flags to see which have the \Recent flag
+           set, or to do a SEARCH RECENT.
+
+      The update from the RECENT response MUST be recorded by the
+      client.
+
+   Example:    S: * 5 RECENT
+
+
+7.4.    Server Responses - Message Status
+
+   These responses are always untagged.  This is how message data are
+   transmitted from the server to the client, often as a result of a
+   command with the same name.  Immediately following the "*" token is a
+   number that represents a message sequence number.
+
+7.4.1.  EXPUNGE Response
+
+   Contents:   none
+
+      The EXPUNGE response reports that the specified message sequence
+      number has been permanently removed from the mailbox.  The message
+      sequence number for each successive message in the mailbox is
+      immediately decremented by 1, and this decrement is reflected in
+      message sequence numbers in subsequent responses (including other
+      untagged EXPUNGE responses).
+
+
+
+
+
+Crispin                     Standards Track                    [Page 72]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      The EXPUNGE response also decrements the number of messages in the
+      mailbox; it is not necessary to send an EXISTS response with the
+      new value.
+
+      As a result of the immediate decrement rule, message sequence
+      numbers that appear in a set of successive EXPUNGE responses
+      depend upon whether the messages are removed starting from lower
+      numbers to higher numbers, or from higher numbers to lower
+      numbers.  For example, if the last 5 messages in a 9-message
+      mailbox are expunged, a "lower to higher" server will send five
+      untagged EXPUNGE responses for message sequence number 5, whereas
+      a "higher to lower server" will send successive untagged EXPUNGE
+      responses for message sequence numbers 9, 8, 7, 6, and 5.
+
+      An EXPUNGE response MUST NOT be sent when no command is in
+      progress, nor while responding to a FETCH, STORE, or SEARCH
+      command.  This rule is necessary to prevent a loss of
+      synchronization of message sequence numbers between client and
+      server.  A command is not "in progress" until the complete command
+      has been received; in particular, a command is not "in progress"
+      during the negotiation of command continuation.
+
+           Note: UID FETCH, UID STORE, and UID SEARCH are different
+           commands from FETCH, STORE, and SEARCH.  An EXPUNGE
+           response MAY be sent during a UID command.
+
+      The update from the EXPUNGE response MUST be recorded by the
+      client.
+
+   Example:    S: * 44 EXPUNGE
+
+
+7.4.2.  FETCH Response
+
+   Contents:   message data
+
+      The FETCH response returns data about a message to the client.
+      The data are pairs of data item names and their values in
+      parentheses.  This response occurs as the result of a FETCH or
+      STORE command, as well as by unilateral server decision (e.g.,
+      flag updates).
+
+      The current data items are:
+
+      BODY
+         A form of BODYSTRUCTURE without extension data.
+
+
+
+
+
+Crispin                     Standards Track                    [Page 73]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      BODY[<section>]<<origin octet>>
+         A string expressing the body contents of the specified section.
+         The string SHOULD be interpreted by the client according to the
+         content transfer encoding, body type, and subtype.
+
+         If the origin octet is specified, this string is a substring of
+         the entire body contents, starting at that origin octet.  This
+         means that BODY[]<0> MAY be truncated, but BODY[] is NEVER
+         truncated.
+
+            Note: The origin octet facility MUST NOT be used by a server
+            in a FETCH response unless the client specifically requested
+            it by means of a FETCH of a BODY[<section>]<<partial>> data
+            item.
+
+         8-bit textual data is permitted if a [CHARSET] identifier is
+         part of the body parameter parenthesized list for this section.
+         Note that headers (part specifiers HEADER or MIME, or the
+         header portion of a MESSAGE/RFC822 part), MUST be 7-bit; 8-bit
+         characters are not permitted in headers.  Note also that the
+         [RFC-2822] delimiting blank line between the header and the
+         body is not affected by header line subsetting; the blank line
+         is always included as part of header data, except in the case
+         of a message which has no body and no blank line.
+
+         Non-textual data such as binary data MUST be transfer encoded
+         into a textual form, such as BASE64, prior to being sent to the
+         client.  To derive the original binary data, the client MUST
+         decode the transfer encoded string.
+
+      BODYSTRUCTURE
+         A parenthesized list that describes the [MIME-IMB] body
+         structure of a message.  This is computed by the server by
+         parsing the [MIME-IMB] header fields, defaulting various fields
+         as necessary.
+
+         For example, a simple text message of 48 lines and 2279 octets
+         can have a body structure of: ("TEXT" "PLAIN" ("CHARSET"
+         "US-ASCII") NIL NIL "7BIT" 2279 48)
+
+         Multiple parts are indicated by parenthesis nesting.  Instead
+         of a body type as the first element of the parenthesized list,
+         there is a sequence of one or more nested body structures.  The
+         second element of the parenthesized list is the multipart
+         subtype (mixed, digest, parallel, alternative, etc.).
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 74]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+         For example, a two part message consisting of a text and a
+         BASE64-encoded text attachment can have a body structure of:
+         (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152
+         23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
+         "<960723163407.20117h@cac.washington.edu>" "Compiler diff"
+         "BASE64" 4554 73) "MIXED")
+
+         Extension data follows the multipart subtype.  Extension data
+         is never returned with the BODY fetch, but can be returned with
+         a BODYSTRUCTURE fetch.  Extension data, if present, MUST be in
+         the defined order.  The extension data of a multipart body part
+         are in the following order:
+
+         body parameter parenthesized list
+            A parenthesized list of attribute/value pairs [e.g., ("foo"
+            "bar" "baz" "rag") where "bar" is the value of "foo", and
+            "rag" is the value of "baz"] as defined in [MIME-IMB].
+
+         body disposition
+            A parenthesized list, consisting of a disposition type
+            string, followed by a parenthesized list of disposition
+            attribute/value pairs as defined in [DISPOSITION].
+
+         body language
+            A string or parenthesized list giving the body language
+            value as defined in [LANGUAGE-TAGS].
+
+         body location
+            A string list giving the body content URI as defined in
+            [LOCATION].
+
+         Any following extension data are not yet defined in this
+         version of the protocol.  Such extension data can consist of
+         zero or more NILs, strings, numbers, or potentially nested
+         parenthesized lists of such data.  Client implementations that
+         do a BODYSTRUCTURE fetch MUST be prepared to accept such
+         extension data.  Server implementations MUST NOT send such
+         extension data until it has been defined by a revision of this
+         protocol.
+
+         The basic fields of a non-multipart body part are in the
+         following order:
+
+         body type
+            A string giving the content media type name as defined in
+            [MIME-IMB].
+
+
+
+
+
+Crispin                     Standards Track                    [Page 75]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+         body subtype
+            A string giving the content subtype name as defined in
+            [MIME-IMB].
+
+         body parameter parenthesized list
+            A parenthesized list of attribute/value pairs [e.g., ("foo"
+            "bar" "baz" "rag") where "bar" is the value of "foo" and
+            "rag" is the value of "baz"] as defined in [MIME-IMB].
+
+         body id
+            A string giving the content id as defined in [MIME-IMB].
+
+         body description
+            A string giving the content description as defined in
+            [MIME-IMB].
+
+         body encoding
+            A string giving the content transfer encoding as defined in
+            [MIME-IMB].
+
+         body size
+            A number giving the size of the body in octets.  Note that
+            this size is the size in its transfer encoding and not the
+            resulting size after any decoding.
+
+         A body type of type MESSAGE and subtype RFC822 contains,
+         immediately after the basic fields, the envelope structure,
+         body structure, and size in text lines of the encapsulated
+         message.
+
+         A body type of type TEXT contains, immediately after the basic
+         fields, the size of the body in text lines.  Note that this
+         size is the size in its content transfer encoding and not the
+         resulting size after any decoding.
+
+         Extension data follows the basic fields and the type-specific
+         fields listed above.  Extension data is never returned with the
+         BODY fetch, but can be returned with a BODYSTRUCTURE fetch.
+         Extension data, if present, MUST be in the defined order.
+
+         The extension data of a non-multipart body part are in the
+         following order:
+
+         body MD5
+            A string giving the body MD5 value as defined in [MD5].
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 76]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+         body disposition
+            A parenthesized list with the same content and function as
+            the body disposition for a multipart body part.
+
+         body language
+            A string or parenthesized list giving the body language
+            value as defined in [LANGUAGE-TAGS].
+
+         body location
+            A string list giving the body content URI as defined in
+            [LOCATION].
+
+         Any following extension data are not yet defined in this
+         version of the protocol, and would be as described above under
+         multipart extension data.
+
+      ENVELOPE
+         A parenthesized list that describes the envelope structure of a
+         message.  This is computed by the server by parsing the
+         [RFC-2822] header into the component parts, defaulting various
+         fields as necessary.
+
+         The fields of the envelope structure are in the following
+         order: date, subject, from, sender, reply-to, to, cc, bcc,
+         in-reply-to, and message-id.  The date, subject, in-reply-to,
+         and message-id fields are strings.  The from, sender, reply-to,
+         to, cc, and bcc fields are parenthesized lists of address
+         structures.
+
+         An address structure is a parenthesized list that describes an
+         electronic mail address.  The fields of an address structure
+         are in the following order: personal name, [SMTP]
+         at-domain-list (source route), mailbox name, and host name.
+
+         [RFC-2822] group syntax is indicated by a special form of
+         address structure in which the host name field is NIL.  If the
+         mailbox name field is also NIL, this is an end of group marker
+         (semi-colon in RFC 822 syntax).  If the mailbox name field is
+         non-NIL, this is a start of group marker, and the mailbox name
+         field holds the group name phrase.
+
+         If the Date, Subject, In-Reply-To, and Message-ID header lines
+         are absent in the [RFC-2822] header, the corresponding member
+         of the envelope is NIL; if these header lines are present but
+         empty the corresponding member of the envelope is the empty
+         string.
+
+
+
+
+
+Crispin                     Standards Track                    [Page 77]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+            Note: some servers may return a NIL envelope member in the
+            "present but empty" case.  Clients SHOULD treat NIL and
+            empty string as identical.
+
+            Note: [RFC-2822] requires that all messages have a valid
+            Date header.  Therefore, the date member in the envelope can
+            not be NIL or the empty string.
+
+            Note: [RFC-2822] requires that the In-Reply-To and
+            Message-ID headers, if present, have non-empty content.
+            Therefore, the in-reply-to and message-id members in the
+            envelope can not be the empty string.
+
+         If the From, To, cc, and bcc header lines are absent in the
+         [RFC-2822] header, or are present but empty, the corresponding
+         member of the envelope is NIL.
+
+         If the Sender or Reply-To lines are absent in the [RFC-2822]
+         header, or are present but empty, the server sets the
+         corresponding member of the envelope to be the same value as
+         the from member (the client is not expected to know to do
+         this).
+
+            Note: [RFC-2822] requires that all messages have a valid
+            From header.  Therefore, the from, sender, and reply-to
+            members in the envelope can not be NIL.
+
+      FLAGS
+         A parenthesized list of flags that are set for this message.
+
+      INTERNALDATE
+         A string representing the internal date of the message.
+
+      RFC822
+         Equivalent to BODY[].
+
+      RFC822.HEADER
+         Equivalent to BODY[HEADER].  Note that this did not result in
+         \Seen being set, because RFC822.HEADER response data occurs as
+         a result of a FETCH of RFC822.HEADER.  BODY[HEADER] response
+         data occurs as a result of a FETCH of BODY[HEADER] (which sets
+         \Seen) or BODY.PEEK[HEADER] (which does not set \Seen).
+
+      RFC822.SIZE
+         A number expressing the [RFC-2822] size of the message.
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 78]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+      RFC822.TEXT
+         Equivalent to BODY[TEXT].
+
+      UID
+         A number expressing the unique identifier of the message.
+
+
+   Example:    S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827)
+
+
+7.5.    Server Responses - Command Continuation Request
+
+   The command continuation request response is indicated by a "+" token
+   instead of a tag.  This form of response indicates that the server is
+   ready to accept the continuation of a command from the client.  The
+   remainder of this response is a line of text.
+
+   This response is used in the AUTHENTICATE command to transmit server
+   data to the client, and request additional client data.  This
+   response is also used if an argument to any command is a literal.
+
+   The client is not permitted to send the octets of the literal unless
+   the server indicates that it is expected.  This permits the server to
+   process commands and reject errors on a line-by-line basis.  The
+   remainder of the command, including the CRLF that terminates a
+   command, follows the octets of the literal.  If there are any
+   additional command arguments, the literal octets are followed by a
+   space and those arguments.
+
+   Example:    C: A001 LOGIN {11}
+               S: + Ready for additional command text
+               C: FRED FOOBAR {7}
+               S: + Ready for additional command text
+               C: fat man
+               S: A001 OK LOGIN completed
+               C: A044 BLURDYBLOOP {102856}
+               S: A044 BAD No such command as "BLURDYBLOOP"
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 79]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+8.      Sample IMAP4rev1 connection
+
+   The following is a transcript of an IMAP4rev1 connection.  A long
+   line in this sample is broken for editorial clarity.
+
+S:   * OK IMAP4rev1 Service Ready
+C:   a001 login mrc secret
+S:   a001 OK LOGIN completed
+C:   a002 select inbox
+S:   * 18 EXISTS
+S:   * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+S:   * 2 RECENT
+S:   * OK [UNSEEN 17] Message 17 is the first unseen message
+S:   * OK [UIDVALIDITY 3857529045] UIDs valid
+S:   a002 OK [READ-WRITE] SELECT completed
+C:   a003 fetch 12 full
+S:   * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700"
+      RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)"
+      "IMAP4rev1 WG mtg summary and minutes"
+      (("Terry Gray" NIL "gray" "cac.washington.edu"))
+      (("Terry Gray" NIL "gray" "cac.washington.edu"))
+      (("Terry Gray" NIL "gray" "cac.washington.edu"))
+      ((NIL NIL "imap" "cac.washington.edu"))
+      ((NIL NIL "minutes" "CNRI.Reston.VA.US")
+      ("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL
+      "<B27397-0100000@cac.washington.edu>")
+       BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028
+       92))
+S:    a003 OK FETCH completed
+C:    a004 fetch 12 body[header]
+S:    * 12 FETCH (BODY[HEADER] {342}
+S:    Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT)
+S:    From: Terry Gray <gray@cac.washington.edu>
+S:    Subject: IMAP4rev1 WG mtg summary and minutes
+S:    To: imap@cac.washington.edu
+S:    cc: minutes@CNRI.Reston.VA.US, John Klensin <KLENSIN@MIT.EDU>
+S:    Message-Id: <B27397-0100000@cac.washington.edu>
+S:    MIME-Version: 1.0
+S:    Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+S:
+S:    )
+S:    a004 OK FETCH completed
+C:    a005 store 12 +flags \deleted
+S:    * 12 FETCH (FLAGS (\Seen \Deleted))
+S:    a005 OK +FLAGS completed
+C:    a006 logout
+S:    * BYE IMAP4rev1 server terminating connection
+S:    a006 OK LOGOUT completed
+
+
+
+Crispin                     Standards Track                    [Page 80]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+9.      Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].
+
+   In the case of alternative or optional rules in which a later rule
+   overlaps an earlier rule, the rule which is listed earlier MUST take
+   priority.  For example, "\Seen" when parsed as a flag is the \Seen
+   flag name and not a flag-extension, even though "\Seen" can be parsed
+   as a flag-extension.  Some, but not all, instances of this rule are
+   noted below.
+
+        Note: [ABNF] rules MUST be followed strictly; in
+        particular:
+
+        (1) Except as noted otherwise, all alphabetic characters
+        are case-insensitive.  The use of upper or lower case
+        characters to define token strings is for editorial clarity
+        only.  Implementations MUST accept these strings in a
+        case-insensitive fashion.
+
+        (2) In all cases, SP refers to exactly one space.  It is
+        NOT permitted to substitute TAB, insert additional spaces,
+        or otherwise treat SP as being equivalent to LWSP.
+
+        (3) The ASCII NUL character, %x00, MUST NOT be used at any
+        time.
+
+address         = "(" addr-name SP addr-adl SP addr-mailbox SP
+                  addr-host ")"
+
+addr-adl        = nstring
+                    ; Holds route from [RFC-2822] route-addr if
+                    ; non-NIL
+
+addr-host       = nstring
+                    ; NIL indicates [RFC-2822] group syntax.
+                    ; Otherwise, holds [RFC-2822] domain name
+
+addr-mailbox    = nstring
+                    ; NIL indicates end of [RFC-2822] group; if
+                    ; non-NIL and addr-host is NIL, holds
+                    ; [RFC-2822] group name.
+                    ; Otherwise, holds [RFC-2822] local-part
+                    ; after removing [RFC-2822] quoting
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 81]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+addr-name       = nstring
+                    ; If non-NIL, holds phrase from [RFC-2822]
+                    ; mailbox after removing [RFC-2822] quoting
+
+append          = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP
+                  literal
+
+astring         = 1*ASTRING-CHAR / string
+
+ASTRING-CHAR   = ATOM-CHAR / resp-specials
+
+atom            = 1*ATOM-CHAR
+
+ATOM-CHAR       = <any CHAR except atom-specials>
+
+atom-specials   = "(" / ")" / "{" / SP / CTL / list-wildcards /
+                  quoted-specials / resp-specials
+
+authenticate    = "AUTHENTICATE" SP auth-type *(CRLF base64)
+
+auth-type       = atom
+                    ; Defined by [SASL]
+
+base64          = *(4base64-char) [base64-terminal]
+
+base64-char     = ALPHA / DIGIT / "+" / "/"
+                    ; Case-sensitive
+
+base64-terminal = (2base64-char "==") / (3base64-char "=")
+
+body            = "(" (body-type-1part / body-type-mpart) ")"
+
+body-extension  = nstring / number /
+                   "(" body-extension *(SP body-extension) ")"
+                    ; Future expansion.  Client implementations
+                    ; MUST accept body-extension fields.  Server
+                    ; implementations MUST NOT generate
+                    ; body-extension fields except as defined by
+                    ; future standard or standards-track
+                    ; revisions of this specification.
+
+body-ext-1part  = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang
+                  [SP body-fld-loc *(SP body-extension)]]]
+                    ; MUST NOT be returned on non-extensible
+                    ; "BODY" fetch
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 82]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+body-ext-mpart  = body-fld-param [SP body-fld-dsp [SP body-fld-lang
+                  [SP body-fld-loc *(SP body-extension)]]]
+                    ; MUST NOT be returned on non-extensible
+                    ; "BODY" fetch
+
+body-fields     = body-fld-param SP body-fld-id SP body-fld-desc SP
+                  body-fld-enc SP body-fld-octets
+
+body-fld-desc   = nstring
+
+body-fld-dsp    = "(" string SP body-fld-param ")" / nil
+
+body-fld-enc    = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
+                  "QUOTED-PRINTABLE") DQUOTE) / string
+
+body-fld-id     = nstring
+
+body-fld-lang   = nstring / "(" string *(SP string) ")"
+
+body-fld-loc    = nstring
+
+body-fld-lines  = number
+
+body-fld-md5    = nstring
+
+body-fld-octets = number
+
+body-fld-param  = "(" string SP string *(SP string SP string) ")" / nil
+
+body-type-1part = (body-type-basic / body-type-msg / body-type-text)
+                  [SP body-ext-1part]
+
+body-type-basic = media-basic SP body-fields
+                    ; MESSAGE subtype MUST NOT be "RFC822"
+
+body-type-mpart = 1*body SP media-subtype
+                  [SP body-ext-mpart]
+
+body-type-msg   = media-message SP body-fields SP envelope
+                  SP body SP body-fld-lines
+
+body-type-text  = media-text SP body-fields SP body-fld-lines
+
+capability      = ("AUTH=" auth-type) / atom
+                    ; New capabilities MUST begin with "X" or be
+                    ; registered with IANA as standard or
+                    ; standards-track
+
+
+
+
+Crispin                     Standards Track                    [Page 83]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+capability-data = "CAPABILITY" *(SP capability) SP "IMAP4rev1"
+                  *(SP capability)
+                    ; Servers MUST implement the STARTTLS, AUTH=PLAIN,
+                    ; and LOGINDISABLED capabilities
+                    ; Servers which offer RFC 1730 compatibility MUST
+                    ; list "IMAP4" as the first capability.
+
+CHAR8           = %x01-ff
+                    ; any OCTET except NUL, %x00
+
+command         = tag SP (command-any / command-auth / command-nonauth /
+                  command-select) CRLF
+                    ; Modal based on state
+
+command-any     = "CAPABILITY" / "LOGOUT" / "NOOP" / x-command
+                    ; Valid in all states
+
+command-auth    = append / create / delete / examine / list / lsub /
+                  rename / select / status / subscribe / unsubscribe
+                    ; Valid only in Authenticated or Selected state
+
+command-nonauth = login / authenticate / "STARTTLS"
+                    ; Valid only when in Not Authenticated state
+
+command-select  = "CHECK" / "CLOSE" / "EXPUNGE" / copy / fetch / store /
+                  uid / search
+                    ; Valid only when in Selected state
+
+continue-req    = "+" SP (resp-text / base64) CRLF
+
+copy            = "COPY" SP sequence-set SP mailbox
+
+create          = "CREATE" SP mailbox
+                    ; Use of INBOX gives a NO error
+
+date            = date-text / DQUOTE date-text DQUOTE
+
+date-day        = 1*2DIGIT
+                    ; Day of month
+
+date-day-fixed  = (SP DIGIT) / 2DIGIT
+                    ; Fixed-format version of date-day
+
+date-month      = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" /
+                  "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec"
+
+date-text       = date-day "-" date-month "-" date-year
+
+
+
+
+Crispin                     Standards Track                    [Page 84]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+date-year       = 4DIGIT
+
+date-time       = DQUOTE date-day-fixed "-" date-month "-" date-year
+                  SP time SP zone DQUOTE
+
+delete          = "DELETE" SP mailbox
+                    ; Use of INBOX gives a NO error
+
+digit-nz        = %x31-39
+                    ; 1-9
+
+envelope        = "(" env-date SP env-subject SP env-from SP
+                  env-sender SP env-reply-to SP env-to SP env-cc SP
+                  env-bcc SP env-in-reply-to SP env-message-id ")"
+
+env-bcc         = "(" 1*address ")" / nil
+
+env-cc          = "(" 1*address ")" / nil
+
+env-date        = nstring
+
+env-from        = "(" 1*address ")" / nil
+
+env-in-reply-to = nstring
+
+env-message-id  = nstring
+
+env-reply-to    = "(" 1*address ")" / nil
+
+env-sender      = "(" 1*address ")" / nil
+
+env-subject     = nstring
+
+env-to          = "(" 1*address ")" / nil
+
+examine         = "EXAMINE" SP mailbox
+
+fetch           = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" /
+                  fetch-att / "(" fetch-att *(SP fetch-att) ")")
+
+fetch-att       = "ENVELOPE" / "FLAGS" / "INTERNALDATE" /
+                  "RFC822" [".HEADER" / ".SIZE" / ".TEXT"] /
+                  "BODY" ["STRUCTURE"] / "UID" /
+                  "BODY" section ["<" number "." nz-number ">"] /
+                  "BODY.PEEK" section ["<" number "." nz-number ">"]
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 85]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+flag            = "\Answered" / "\Flagged" / "\Deleted" /
+                  "\Seen" / "\Draft" / flag-keyword / flag-extension
+                    ; Does not include "\Recent"
+
+flag-extension  = "\" atom
+                    ; Future expansion.  Client implementations
+                    ; MUST accept flag-extension flags.  Server
+                    ; implementations MUST NOT generate
+                    ; flag-extension flags except as defined by
+                    ; future standard or standards-track
+                    ; revisions of this specification.
+
+flag-fetch      = flag / "\Recent"
+
+flag-keyword    = atom
+
+flag-list       = "(" [flag *(SP flag)] ")"
+
+flag-perm       = flag / "\*"
+
+greeting        = "*" SP (resp-cond-auth / resp-cond-bye) CRLF
+
+header-fld-name = astring
+
+header-list     = "(" header-fld-name *(SP header-fld-name) ")"
+
+list            = "LIST" SP mailbox SP list-mailbox
+
+list-mailbox    = 1*list-char / string
+
+list-char       = ATOM-CHAR / list-wildcards / resp-specials
+
+list-wildcards  = "%" / "*"
+
+literal         = "{" number "}" CRLF *CHAR8
+                    ; Number represents the number of CHAR8s
+
+login           = "LOGIN" SP userid SP password
+
+lsub            = "LSUB" SP mailbox SP list-mailbox
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 86]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+mailbox         = "INBOX" / astring
+                    ; INBOX is case-insensitive.  All case variants of
+                    ; INBOX (e.g., "iNbOx") MUST be interpreted as INBOX
+                    ; not as an astring.  An astring which consists of
+                    ; the case-insensitive sequence "I" "N" "B" "O" "X"
+                    ; is considered to be INBOX and not an astring.
+                    ;  Refer to section 5.1 for further
+                    ; semantic details of mailbox names.
+
+mailbox-data    =  "FLAGS" SP flag-list / "LIST" SP mailbox-list /
+                   "LSUB" SP mailbox-list / "SEARCH" *(SP nz-number) /
+                   "STATUS" SP mailbox SP "(" [status-att-list] ")" /
+                   number SP "EXISTS" / number SP "RECENT"
+
+mailbox-list    = "(" [mbx-list-flags] ")" SP
+                   (DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox
+
+mbx-list-flags  = *(mbx-list-oflag SP) mbx-list-sflag
+                  *(SP mbx-list-oflag) /
+                  mbx-list-oflag *(SP mbx-list-oflag)
+
+mbx-list-oflag  = "\Noinferiors" / flag-extension
+                    ; Other flags; multiple possible per LIST response
+
+mbx-list-sflag  = "\Noselect" / "\Marked" / "\Unmarked"
+                    ; Selectability flags; only one per LIST response
+
+media-basic     = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" /
+                  "MESSAGE" / "VIDEO") DQUOTE) / string) SP
+                  media-subtype
+                    ; Defined in [MIME-IMT]
+
+media-message   = DQUOTE "MESSAGE" DQUOTE SP DQUOTE "RFC822" DQUOTE
+                    ; Defined in [MIME-IMT]
+
+media-subtype   = string
+                    ; Defined in [MIME-IMT]
+
+media-text      = DQUOTE "TEXT" DQUOTE SP media-subtype
+                    ; Defined in [MIME-IMT]
+
+message-data    = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att))
+
+msg-att         = "(" (msg-att-dynamic / msg-att-static)
+                   *(SP (msg-att-dynamic / msg-att-static)) ")"
+
+msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")"
+                    ; MAY change for a message
+
+
+
+Crispin                     Standards Track                    [Page 87]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+msg-att-static  = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time /
+                  "RFC822" [".HEADER" / ".TEXT"] SP nstring /
+                  "RFC822.SIZE" SP number /
+                  "BODY" ["STRUCTURE"] SP body /
+                  "BODY" section ["<" number ">"] SP nstring /
+                  "UID" SP uniqueid
+                    ; MUST NOT change for a message
+
+nil             = "NIL"
+
+nstring         = string / nil
+
+number          = 1*DIGIT
+                    ; Unsigned 32-bit integer
+                    ; (0 <= n < 4,294,967,296)
+
+nz-number       = digit-nz *DIGIT
+                    ; Non-zero unsigned 32-bit integer
+                    ; (0 < n < 4,294,967,296)
+
+password        = astring
+
+quoted          = DQUOTE *QUOTED-CHAR DQUOTE
+
+QUOTED-CHAR     = <any TEXT-CHAR except quoted-specials> /
+                  "\" quoted-specials
+
+quoted-specials = DQUOTE / "\"
+
+rename          = "RENAME" SP mailbox SP mailbox
+                    ; Use of INBOX as a destination gives a NO error
+
+response        = *(continue-req / response-data) response-done
+
+response-data   = "*" SP (resp-cond-state / resp-cond-bye /
+                  mailbox-data / message-data / capability-data) CRLF
+
+response-done   = response-tagged / response-fatal
+
+response-fatal  = "*" SP resp-cond-bye CRLF
+                    ; Server closes connection immediately
+
+response-tagged = tag SP resp-cond-state CRLF
+
+resp-cond-auth  = ("OK" / "PREAUTH") SP resp-text
+                    ; Authentication condition
+
+
+
+
+
+Crispin                     Standards Track                    [Page 88]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+resp-cond-bye   = "BYE" SP resp-text
+
+resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text
+                    ; Status condition
+
+resp-specials   = "]"
+
+resp-text       = ["[" resp-text-code "]" SP] text
+
+resp-text-code  = "ALERT" /
+                  "BADCHARSET" [SP "(" astring *(SP astring) ")" ] /
+                  capability-data / "PARSE" /
+                  "PERMANENTFLAGS" SP "("
+                  [flag-perm *(SP flag-perm)] ")" /
+                  "READ-ONLY" / "READ-WRITE" / "TRYCREATE" /
+                  "UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number /
+                  "UNSEEN" SP nz-number /
+                  atom [SP 1*<any TEXT-CHAR except "]">]
+
+search          = "SEARCH" [SP "CHARSET" SP astring] 1*(SP search-key)
+                    ; CHARSET argument to MUST be registered with IANA
+
+search-key      = "ALL" / "ANSWERED" / "BCC" SP astring /
+                  "BEFORE" SP date / "BODY" SP astring /
+                  "CC" SP astring / "DELETED" / "FLAGGED" /
+                  "FROM" SP astring / "KEYWORD" SP flag-keyword /
+                  "NEW" / "OLD" / "ON" SP date / "RECENT" / "SEEN" /
+                  "SINCE" SP date / "SUBJECT" SP astring /
+                  "TEXT" SP astring / "TO" SP astring /
+                  "UNANSWERED" / "UNDELETED" / "UNFLAGGED" /
+                  "UNKEYWORD" SP flag-keyword / "UNSEEN" /
+                    ; Above this line were in [IMAP2]
+                  "DRAFT" / "HEADER" SP header-fld-name SP astring /
+                  "LARGER" SP number / "NOT" SP search-key /
+                  "OR" SP search-key SP search-key /
+                  "SENTBEFORE" SP date / "SENTON" SP date /
+                  "SENTSINCE" SP date / "SMALLER" SP number /
+                  "UID" SP sequence-set / "UNDRAFT" / sequence-set /
+                  "(" search-key *(SP search-key) ")"
+
+section         = "[" [section-spec] "]"
+
+section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list /
+                  "TEXT"
+                    ; top-level or MESSAGE/RFC822 part
+
+section-part    = nz-number *("." nz-number)
+                    ; body part nesting
+
+
+
+Crispin                     Standards Track                    [Page 89]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+section-spec    = section-msgtext / (section-part ["." section-text])
+
+section-text    = section-msgtext / "MIME"
+                    ; text other than actual body part (headers, etc.)
+
+select          = "SELECT" SP mailbox
+
+seq-number      = nz-number / "*"
+                    ; message sequence number (COPY, FETCH, STORE
+                    ; commands) or unique identifier (UID COPY,
+                    ; UID FETCH, UID STORE commands).
+                    ; * represents the largest number in use.  In
+                    ; the case of message sequence numbers, it is
+                    ; the number of messages in a non-empty mailbox.
+                    ; In the case of unique identifiers, it is the
+                    ; unique identifier of the last message in the
+                    ; mailbox or, if the mailbox is empty, the
+                    ; mailbox's current UIDNEXT value.
+                    ; The server should respond with a tagged BAD
+                    ; response to a command that uses a message
+                    ; sequence number greater than the number of
+                    ; messages in the selected mailbox.  This
+                    ; includes "*" if the selected mailbox is empty.
+
+seq-range       = seq-number ":" seq-number
+                    ; two seq-number values and all values between
+                    ; these two regardless of order.
+                    ; Example: 2:4 and 4:2 are equivalent and indicate
+                    ; values 2, 3, and 4.
+                    ; Example: a unique identifer sequence range of
+                    ; 3291:* includes the UID of the last message in
+                    ; the mailbox, even if that value is less than 3291.
+
+sequence-set    = (seq-number / seq-range) *("," sequence-set)
+                    ; set of seq-number values, regardless of order.
+                    ; Servers MAY coalesce overlaps and/or execute the
+                    ; sequence in any order.
+                    ; Example: a message sequence number set of
+                    ; 2,4:7,9,12:* for a mailbox with 15 messages is
+                    ; equivalent to 2,4,5,6,7,9,12,13,14,15
+                    ; Example: a message sequence number set of *:4,5:7
+                    ; for a mailbox with 10 messages is equivalent to
+                    ; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and
+                    ; overlap coalesced to be 4,5,6,7,8,9,10.
+
+status          = "STATUS" SP mailbox SP
+                  "(" status-att *(SP status-att) ")"
+
+
+
+
+Crispin                     Standards Track                    [Page 90]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+status-att      = "MESSAGES" / "RECENT" / "UIDNEXT" / "UIDVALIDITY" /
+                  "UNSEEN"
+
+status-att-list =  status-att SP number *(SP status-att SP number)
+
+store           = "STORE" SP sequence-set SP store-att-flags
+
+store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP
+                  (flag-list / (flag *(SP flag)))
+
+string          = quoted / literal
+
+subscribe       = "SUBSCRIBE" SP mailbox
+
+tag             = 1*<any ASTRING-CHAR except "+">
+
+text            = 1*TEXT-CHAR
+
+TEXT-CHAR       = <any CHAR except CR and LF>
+
+time            = 2DIGIT ":" 2DIGIT ":" 2DIGIT
+                    ; Hours minutes seconds
+
+uid             = "UID" SP (copy / fetch / search / store)
+                    ; Unique identifiers used instead of message
+                    ; sequence numbers
+
+uniqueid        = nz-number
+                    ; Strictly ascending
+
+unsubscribe     = "UNSUBSCRIBE" SP mailbox
+
+userid          = astring
+
+x-command       = "X" atom <experimental command arguments>
+
+zone            = ("+" / "-") 4DIGIT
+                    ; Signed four-digit value of hhmm representing
+                    ; hours and minutes east of Greenwich (that is,
+                    ; the amount that the given time differs from
+                    ; Universal Time).  Subtracting the timezone
+                    ; from the given time will give the UT form.
+                    ; The Universal Time zone is "+0000".
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 91]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+10.     Author's Note
+
+   This document is a revision or rewrite of earlier documents, and
+   supercedes the protocol specification in those documents: RFC 2060,
+   RFC 1730, unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064.
+
+11.     Security Considerations
+
+   IMAP4rev1 protocol transactions, including electronic mail data, are
+   sent in the clear over the network unless protection from snooping is
+   negotiated.  This can be accomplished either by the use of STARTTLS,
+   negotiated privacy protection in the AUTHENTICATE command, or some
+   other protection mechanism.
+
+11.1.   STARTTLS Security Considerations
+
+   The specification of the STARTTLS command and LOGINDISABLED
+   capability in this document replaces that in [IMAP-TLS].  [IMAP-TLS]
+   remains normative for the PLAIN [SASL] authenticator.
+
+   IMAP client and server implementations MUST implement the
+   TLS_RSA_WITH_RC4_128_MD5 [TLS] cipher suite, and SHOULD implement the
+   TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher suite.  This is
+   important as it assures that any two compliant implementations can be
+   configured to interoperate.  All other cipher suites are OPTIONAL.
+   Note that this is a change from section 2.1 of [IMAP-TLS].
+
+   During the [TLS] negotiation, the client MUST check its understanding
+   of the server hostname against the server's identity as presented in
+   the server Certificate message, in order to prevent man-in-the-middle
+   attacks.  If the match fails, the client SHOULD either ask for
+   explicit user confirmation, or terminate the connection and indicate
+   that the server's identity is suspect.  Matching is performed
+   according to these rules:
+
+        The client MUST use the server hostname it used to open the
+        connection as the value to compare against the server name
+        as expressed in the server certificate.  The client MUST
+        NOT use any form of the server hostname derived from an
+        insecure remote source (e.g., insecure DNS lookup).  CNAME
+        canonicalization is not done.
+
+        If a subjectAltName extension of type dNSName is present in
+        the certificate, it SHOULD be used as the source of the
+        server's identity.
+
+        Matching is case-insensitive.
+
+
+
+
+Crispin                     Standards Track                    [Page 92]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+        A "*" wildcard character MAY be used as the left-most name
+        component in the certificate.  For example, *.example.com
+        would match a.example.com, foo.example.com, etc. but would
+        not match example.com.
+
+        If the certificate contains multiple names (e.g., more than
+        one dNSName field), then a match with any one of the fields
+        is considered acceptable.
+
+   Both the client and server MUST check the result of the STARTTLS
+   command and subsequent [TLS] negotiation to see whether acceptable
+   authentication or privacy was achieved.
+
+11.2.   Other Security Considerations
+
+   A server error message for an AUTHENTICATE command which fails due to
+   invalid credentials SHOULD NOT detail why the credentials are
+   invalid.
+
+   Use of the LOGIN command sends passwords in the clear.  This can be
+   avoided by using the AUTHENTICATE command with a [SASL] mechanism
+   that does not use plaintext passwords, by first negotiating
+   encryption via STARTTLS or some other protection mechanism.
+
+   A server implementation MUST implement a configuration that, at the
+   time of authentication, requires:
+      (1) The STARTTLS command has been negotiated.
+   OR
+      (2) Some other mechanism that protects the session from password
+      snooping has been provided.
+   OR
+      (3) The following measures are in place:
+         (a) The LOGINDISABLED capability is advertised, and [SASL]
+         mechanisms (such as PLAIN) using plaintext passwords are NOT
+         advertised in the CAPABILITY list.
+      AND
+         (b) The LOGIN command returns an error even if the password is
+         correct.
+      AND
+         (c) The AUTHENTICATE command returns an error with all [SASL]
+         mechanisms that use plaintext passwords, even if the password
+         is correct.
+
+   A server error message for a failing LOGIN command SHOULD NOT specify
+   that the user name, as opposed to the password, is invalid.
+
+   A server SHOULD have mechanisms in place to limit or delay failed
+   AUTHENTICATE/LOGIN attempts.
+
+
+
+Crispin                     Standards Track                    [Page 93]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   Additional security considerations are discussed in the section
+   discussing the AUTHENTICATE and LOGIN commands.
+
+12.     IANA Considerations
+
+   IMAP4 capabilities are registered by publishing a standards track or
+   IESG approved experimental RFC.  The registry is currently located
+   at:
+
+        http://www.iana.org/assignments/imap4-capabilities
+
+   As this specification revises the STARTTLS and LOGINDISABLED
+   extensions previously defined in [IMAP-TLS], the registry will be
+   updated accordingly.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 94]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+Appendices
+
+A.      Normative References
+
+   The following documents contain definitions or specifications that
+   are necessary to understand this document properly:
+   [ABNF]                Crocker, D. and P. Overell, "Augmented BNF for
+                         Syntax Specifications: ABNF", RFC 2234,
+                         November 1997.
+
+   [ANONYMOUS]           Newman, C., "Anonymous SASL Mechanism", RFC
+                         2245, November 1997.
+
+   [CHARSET]             Freed, N. and J. Postel, "IANA Character Set
+                         Registration Procedures", RFC 2978, October
+                         2000.
+
+   [DIGEST-MD5]          Leach, P. and C. Newman, "Using Digest
+                         Authentication as a SASL Mechanism", RFC 2831,
+                         May 2000.
+
+   [DISPOSITION]         Troost, R., Dorner, S. and K. Moore,
+                         "Communicating Presentation Information in
+                         Internet Messages: The Content-Disposition
+                         Header", RFC 2183, August 1997.
+
+   [IMAP-TLS]            Newman, C., "Using TLS with IMAP, POP3 and
+                         ACAP", RFC 2595, June 1999.
+
+   [KEYWORDS]            Bradner, S., "Key words for use in RFCs to
+                         Indicate Requirement Levels", BCP 14, RFC 2119,
+                         March 1997.
+
+   [LANGUAGE-TAGS]       Alvestrand, H., "Tags for the Identification of
+                         Languages", BCP 47, RFC 3066, January 2001.
+
+   [LOCATION]            Palme, J., Hopmann, A. and N. Shelness, "MIME
+                         Encapsulation of Aggregate Documents, such as
+                         HTML (MHTML)", RFC 2557, March 1999.
+
+   [MD5]                 Myers, J. and M. Rose, "The Content-MD5 Header
+                         Field", RFC 1864, October 1995.
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 95]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   [MIME-HDRS]           Moore, K., "MIME (Multipurpose Internet Mail
+                         Extensions) Part Three: Message Header
+                         Extensions for Non-ASCII Text", RFC 2047,
+                         November 1996.
+
+   [MIME-IMB]            Freed, N. and N. Borenstein, "MIME
+                         (Multipurpose Internet Mail Extensions) Part
+                         One: Format of Internet Message Bodies", RFC
+                         2045, November 1996.
+
+   [MIME-IMT]            Freed, N. and N. Borenstein, "MIME
+                         (Multipurpose Internet Mail Extensions) Part
+                         Two: Media Types", RFC 2046, November 1996.
+
+   [RFC-2822]            Resnick, P., "Internet Message Format", RFC
+                         2822, April 2001.
+
+   [SASL]                Myers, J., "Simple Authentication and Security
+                         Layer (SASL)", RFC 2222, October 1997.
+
+   [TLS]                 Dierks, T. and C. Allen, "The TLS Protocol
+                         Version 1.0", RFC 2246, January 1999.
+
+   [UTF-7]               Goldsmith, D. and M. Davis, "UTF-7: A Mail-Safe
+                         Transformation Format of Unicode", RFC 2152,
+                         May 1997.
+
+   The following documents describe quality-of-implementation issues
+   that should be carefully considered when implementing this protocol:
+
+   [IMAP-IMPLEMENTATION] Leiba, B., "IMAP Implementation
+                         Recommendations", RFC 2683, September 1999.
+
+   [IMAP-MULTIACCESS]    Gahrns, M., "IMAP4 Multi-Accessed Mailbox
+                         Practice", RFC 2180, July 1997.
+
+A.1     Informative References
+
+   The following documents describe related protocols:
+
+   [IMAP-DISC]           Austein, R., "Synchronization Operations for
+                         Disconnected IMAP4 Clients", Work in Progress.
+
+   [IMAP-MODEL]          Crispin, M., "Distributed Electronic Mail
+                         Models in IMAP4", RFC 1733, December 1994.
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 96]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   [ACAP]                Newman, C. and J. Myers, "ACAP -- Application
+                         Configuration Access Protocol", RFC 2244,
+                         November 1997.
+
+   [SMTP]                Klensin, J., "Simple Mail Transfer Protocol",
+                         STD 10, RFC 2821, April 2001.
+
+   The following documents are historical or describe historical aspects
+   of this protocol:
+
+   [IMAP-COMPAT]         Crispin, M., "IMAP4 Compatibility with
+                         IMAP2bis", RFC 2061, December 1996.
+
+   [IMAP-HISTORICAL]     Crispin, M., "IMAP4 Compatibility with IMAP2
+                         and IMAP2bis", RFC 1732, December 1994.
+
+   [IMAP-OBSOLETE]       Crispin, M., "Internet Message Access Protocol
+                         - Obsolete Syntax", RFC 2062, December 1996.
+
+   [IMAP2]               Crispin, M., "Interactive Mail Access Protocol
+                         - Version 2", RFC 1176, August 1990.
+
+   [RFC-822]             Crocker, D., "Standard for the Format of ARPA
+                         Internet Text Messages", STD 11, RFC 822,
+                         August 1982.
+
+   [RFC-821]             Postel, J., "Simple Mail Transfer Protocol",
+                         STD 10, RFC 821, August 1982.
+
+B.      Changes from RFC 2060
+
+   1) Clarify description of unique identifiers and their semantics.
+
+   2) Fix the SELECT description to clarify that UIDVALIDITY is required
+   in the SELECT and EXAMINE responses.
+
+   3) Added an example of a failing search.
+
+   4) Correct store-att-flags: "#flag" should be "1#flag".
+
+   5) Made search and section rules clearer.
+
+   6) Correct the STORE example.
+
+   7) Correct "BASE645" misspelling.
+
+   8) Remove extraneous close parenthesis in example of two-part message
+   with text and BASE64 attachment.
+
+
+
+Crispin                     Standards Track                    [Page 97]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   9) Remove obsolete "MAILBOX" response from mailbox-data.
+
+   10) A spurious "<" in the rule for mailbox-data was removed.
+
+   11) Add CRLF to continue-req.
+
+   12) Specifically exclude "]" from the atom in resp-text-code.
+
+   13) Clarify that clients and servers should adhere strictly to the
+   protocol syntax.
+
+   14) Emphasize in 5.2 that EXISTS can not be used to shrink a mailbox.
+
+   15) Add NEWNAME to resp-text-code.
+
+   16) Clarify that the empty string, not NIL, is used as arguments to
+   LIST.
+
+   17) Clarify that NIL can be returned as a hierarchy delimiter for the
+   empty string mailbox name argument if the mailbox namespace is flat.
+
+   18) Clarify that addr-mailbox and addr-name have RFC-2822 quoting
+   removed.
+
+   19) Update UTF-7 reference.
+
+   20) Fix example in 6.3.11.
+
+   21) Clarify that non-existent UIDs are ignored.
+
+   22) Update DISPOSITION reference.
+
+   23) Expand state diagram.
+
+   24) Clarify that partial fetch responses are only returned in
+   response to a partial fetch command.
+
+   25) Add UIDNEXT response code.  Correct UIDVALIDITY definition
+   reference.
+
+   26) Further clarification of "can" vs. "MAY".
+
+   27) Reference RFC-2119.
+
+   28) Clarify that superfluous shifts are not permitted in modified
+   UTF-7.
+
+   29) Clarify that there are no implicit shifts in modified UTF-7.
+
+
+
+Crispin                     Standards Track                    [Page 98]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   30) Clarify that "INBOX" in a mailbox name is always INBOX, even if
+   it is given as a string.
+
+   31) Add missing open parenthesis in media-basic grammar rule.
+
+   32) Correct attribute syntax in mailbox-data.
+
+   33) Add UIDNEXT to EXAMINE responses.
+
+   34) Clarify UNSEEN, PERMANENTFLAGS, UIDVALIDITY, and UIDNEXT
+   responses in SELECT and EXAMINE.  They are required now, but weren't
+   in older versions.
+
+   35) Update references with RFC numbers.
+
+   36) Flush text-mime2.
+
+   37) Clarify that modified UTF-7 names must be case-sensitive and that
+   violating the convention should be avoided.
+
+   38) Correct UID FETCH example.
+
+   39) Clarify UID FETCH, UID STORE, and UID SEARCH vs. untagged EXPUNGE
+   responses.
+
+   40) Clarify the use of the word "convention".
+
+   41) Clarify that a command is not "in progress" until it has been
+   fully received (specifically, that a command is not "in progress"
+   during command continuation negotiation).
+
+   42) Clarify envelope defaulting.
+
+   43) Clarify that SP means one and only one space character.
+
+   44) Forbid silly states in LIST response.
+
+   45) Clarify that the ENVELOPE, INTERNALDATE, RFC822*, BODY*, and UID
+   for a message is static.
+
+   46) Add BADCHARSET response code.
+
+   47) Update formal syntax to [ABNF] conventions.
+
+   48) Clarify trailing hierarchy delimiter in CREATE semantics.
+
+   49) Clarify that the "blank line" is the [RFC-2822] delimiting blank
+   line.
+
+
+
+Crispin                     Standards Track                    [Page 99]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   50) Clarify that RENAME should also create hierarchy as needed for
+   the command to complete.
+
+   51) Fix body-ext-mpart to not require language if disposition
+   present.
+
+   52) Clarify the RFC822.HEADER response.
+
+   53) Correct missing space after charset astring in search.
+
+   54) Correct missing quote for BADCHARSET in resp-text-code.
+
+   55) Clarify that ALL, FAST, and FULL preclude any other data items
+   appearing.
+
+   56) Clarify semantics of reference argument in LIST.
+
+   57) Clarify that a null string for SEARCH HEADER X-FOO means any
+   message with a header line with a field-name of X-FOO regardless of
+   the text of the header.
+
+   58) Specifically reserve 8-bit mailbox names for future use as UTF-8.
+
+   59) It is not an error for the client to store a flag that is not in
+   the PERMANENTFLAGS list; however, the server will either ignore the
+   change or make the change in the session only.
+
+   60) Correct/clarify the text regarding superfluous shifts.
+
+   61) Correct typographic errors in the "Changes" section.
+
+   62) Clarify that STATUS must not be used to check for new messages in
+   the selected mailbox
+
+   63) Clarify LSUB behavior with "%" wildcard.
+
+   64) Change AUTHORIZATION to AUTHENTICATE in section 7.5.
+
+   65) Clarify description of multipart body type.
+
+   66) Clarify that STORE FLAGS does not affect \Recent.
+
+   67) Change "west" to "east" in description of timezone.
+
+   68) Clarify that commands which break command pipelining must wait
+   for a completion result response.
+
+   69) Clarify that EXAMINE does not affect \Recent.
+
+
+
+Crispin                     Standards Track                   [Page 100]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   70) Make description of MIME structure consistent.
+
+   71) Clarify that date searches disregard the time and timezone of the
+   INTERNALDATE or Date: header.  In other words, "ON 13-APR-2000" means
+   messages with an INTERNALDATE text which starts with "13-APR-2000",
+   even if timezone differential from the local timezone is sufficient
+   to move that INTERNALDATE into the previous or next day.
+
+   72) Clarify that the header fetches don't add a blank line if one
+   isn't in the [RFC-2822] message.
+
+   73) Clarify (in discussion of UIDs) that messages are immutable.
+
+   74) Add an example of CHARSET searching.
+
+   75) Clarify in SEARCH that keywords are a type of flag.
+
+   76) Clarify the mandatory nature of the SELECT data responses.
+
+   77) Add optional CAPABILITY response code in the initial OK or
+   PREAUTH.
+
+   78) Add note that server can send an untagged CAPABILITY command as
+   part of the responses to AUTHENTICATE and LOGIN.
+
+   79) Remove statement about it being unnecessary to issue a CAPABILITY
+   command more than once in a connection.  That statement is no longer
+   true.
+
+   80) Clarify that untagged EXPUNGE decrements the number of messages
+   in the mailbox.
+
+   81) Fix definition of "body" (concatenation has tighter binding than
+   alternation).
+
+   82) Add a new "Special Notes to Implementors" section with reference
+   to [IMAP-IMPLEMENTATION].
+
+   83) Clarify that an untagged CAPABILITY response to an AUTHENTICATE
+   command should only be done if a security layer was not negotiated.
+
+   84) Change the definition of atom to exclude "]".  Update astring to
+   include "]" for compatiblity with the past.  Remove resp-text-atom.
+
+   85) Remove NEWNAME.  It can't work because mailbox names can be
+   literals and can include "]".  Functionality can be addressed via
+   referrals.
+
+
+
+
+Crispin                     Standards Track                   [Page 101]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   86) Move modified UTF-7 rationale in order to have more logical
+   paragraph flow.
+
+   87) Clarify UID uniqueness guarantees with the use of MUST.
+
+   88) Note that clients should read response data until the connection
+   is closed instead of immediately closing on a BYE.
+
+   89) Change RFC-822 references to RFC-2822.
+
+   90) Clarify that RFC-2822 should be followed instead of RFC-822.
+
+   91) Change recommendation of optional automatic capabilities in LOGIN
+   and AUTHENTICATE to use the CAPABILITY response code in the tagged
+   OK.  This is more interoperable than an unsolicited untagged
+   CAPABILITY response.
+
+   92) STARTTLS and AUTH=PLAIN are mandatory to implement; add
+   recommendations for other [SASL] mechanisms.
+
+   93) Clarify that a "connection" (as opposed to "server" or "command")
+   is in one of the four states.
+
+   94) Clarify that a failed or rejected command does not change state.
+
+   95) Split references between normative and informative.
+
+   96) Discuss authentication failure issues in security section.
+
+   97) Clarify that a data item is not necessarily of only one data
+   type.
+
+   98) Clarify that sequence ranges are independent of order.
+
+   99) Change an example to clarify that superfluous shifts in
+   Modified-UTF7 can not be fixed just by omitting the shift.  The
+   entire string must be recalculated.
+
+   100) Change Envelope Structure definition since [RFC-2822] uses
+   "envelope" to refer to the [SMTP] envelope and not the envelope data
+   that appears in the [RFC-2822] header.
+
+   101) Expand on RFC822.HEADER response data vs. BODY[HEADER].
+
+   102) Clarify Logout state semantics, change ASCII art.
+
+   103) Security changes to comply with IESG requirements.
+
+
+
+
+Crispin                     Standards Track                   [Page 102]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+   104) Add definition for body URI.
+
+   105) Break sequence range definition into three rules, with rewritten
+   descriptions for each.
+
+   106) Move STARTTLS and LOGINDISABLED here from [IMAP-TLS].
+
+   107) Add IANA Considerations section.
+
+   108) Clarify valid client assumptions for new message UIDs vs.
+   UIDNEXT.
+
+   109) Clarify that changes to permanentflags affect concurrent
+   sessions as well as subsequent sessions.
+
+   110) Clarify that authenticated state can be entered by the CLOSE
+   command.
+
+   111) Emphasize that SELECT and EXAMINE are the exceptions to the rule
+   that a failing command does not change state.
+
+   112) Clarify that newly-appended messages have the Recent flag set.
+
+   113) Clarify that newly-copied messages SHOULD have the Recent flag
+   set.
+
+   114) Clarify that UID commands always return the UID in FETCH
+   responses.
+
+C.      Key Word Index
+
+       +FLAGS <flag list> (store command data item) ...............   59
+       +FLAGS.SILENT <flag list> (store command data item) ........   59
+       -FLAGS <flag list> (store command data item) ...............   59
+       -FLAGS.SILENT <flag list> (store command data item) ........   59
+       ALERT (response code) ......................................   64
+       ALL (fetch item) ...........................................   55
+       ALL (search key) ...........................................   50
+       ANSWERED (search key) ......................................   50
+       APPEND (command) ...........................................   45
+       AUTHENTICATE (command) .....................................   27
+       BAD (response) .............................................   66
+       BADCHARSET (response code) .................................   64
+       BCC <string> (search key) ..................................   51
+       BEFORE <date> (search key) .................................   51
+       BODY (fetch item) ..........................................   55
+       BODY (fetch result) ........................................   73
+       BODY <string> (search key) .................................   51
+
+
+
+Crispin                     Standards Track                   [Page 103]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+       BODY.PEEK[<section>]<<partial>> (fetch item) ...............   57
+       BODYSTRUCTURE (fetch item) .................................   57
+       BODYSTRUCTURE (fetch result) ...............................   74
+       BODY[<section>]<<origin octet>> (fetch result) .............   74
+       BODY[<section>]<<partial>> (fetch item) ....................   55
+       BYE (response) .............................................   67
+       Body Structure (message attribute) .........................   12
+       CAPABILITY (command) .......................................   24
+       CAPABILITY (response code) .................................   64
+       CAPABILITY (response) ......................................   68
+       CC <string> (search key) ...................................   51
+       CHECK (command) ............................................   47
+       CLOSE (command) ............................................   48
+       COPY (command) .............................................   59
+       CREATE (command) ...........................................   34
+       DELETE (command) ...........................................   35
+       DELETED (search key) .......................................   51
+       DRAFT (search key) .........................................   51
+       ENVELOPE (fetch item) ......................................   57
+       ENVELOPE (fetch result) ....................................   77
+       EXAMINE (command) ..........................................   33
+       EXISTS (response) ..........................................   71
+       EXPUNGE (command) ..........................................   48
+       EXPUNGE (response) .........................................   72
+       Envelope Structure (message attribute) .....................   12
+       FAST (fetch item) ..........................................   55
+       FETCH (command) ............................................   54
+       FETCH (response) ...........................................   73
+       FLAGGED (search key) .......................................   51
+       FLAGS (fetch item) .........................................   57
+       FLAGS (fetch result) .......................................   78
+       FLAGS (response) ...........................................   71
+       FLAGS <flag list> (store command data item) ................   59
+       FLAGS.SILENT <flag list> (store command data item) .........   59
+       FROM <string> (search key) .................................   51
+       FULL (fetch item) ..........................................   55
+       Flags (message attribute) ..................................   11
+       HEADER (part specifier) ....................................   55
+       HEADER <field-name> <string> (search key) ..................   51
+       HEADER.FIELDS <header-list> (part specifier) ...............   55
+       HEADER.FIELDS.NOT <header-list> (part specifier) ...........   55
+       INTERNALDATE (fetch item) ..................................   57
+       INTERNALDATE (fetch result) ................................   78
+       Internal Date (message attribute) ..........................   12
+       KEYWORD <flag> (search key) ................................   51
+       Keyword (type of flag) .....................................   11
+       LARGER <n> (search key) ....................................   51
+       LIST (command) .............................................   40
+
+
+
+Crispin                     Standards Track                   [Page 104]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+       LIST (response) ............................................   69
+       LOGIN (command) ............................................   30
+       LOGOUT (command) ...........................................   25
+       LSUB (command) .............................................   43
+       LSUB (response) ............................................   70
+       MAY (specification requirement term) .......................    4
+       MESSAGES (status item) .....................................   45
+       MIME (part specifier) ......................................   56
+       MUST (specification requirement term) ......................    4
+       MUST NOT (specification requirement term) ..................    4
+       Message Sequence Number (message attribute) ................   10
+       NEW (search key) ...........................................   51
+       NO (response) ..............................................   66
+       NOOP (command) .............................................   25
+       NOT <search-key> (search key) ..............................   52
+       OK (response) ..............................................   65
+       OLD (search key) ...........................................   52
+       ON <date> (search key) .....................................   52
+       OPTIONAL (specification requirement term) ..................    4
+       OR <search-key1> <search-key2> (search key) ................   52
+       PARSE (response code) ......................................   64
+       PERMANENTFLAGS (response code) .............................   64
+       PREAUTH (response) .........................................   67
+       Permanent Flag (class of flag) .............................   12
+       READ-ONLY (response code) ..................................   65
+       READ-WRITE (response code) .................................   65
+       RECENT (response) ..........................................   72
+       RECENT (search key) ........................................   52
+       RECENT (status item) .......................................   45
+       RENAME (command) ...........................................   37
+       REQUIRED (specification requirement term) ..................    4
+       RFC822 (fetch item) ........................................   57
+       RFC822 (fetch result) ......................................   78
+       RFC822.HEADER (fetch item) .................................   57
+       RFC822.HEADER (fetch result) ...............................   78
+       RFC822.SIZE (fetch item) ...................................   57
+       RFC822.SIZE (fetch result) .................................   78
+       RFC822.TEXT (fetch item) ...................................   58
+       RFC822.TEXT (fetch result) .................................   79
+       SEARCH (command) ...........................................   49
+       SEARCH (response) ..........................................   71
+       SEEN (search key) ..........................................   52
+       SELECT (command) ...........................................   31
+       SENTBEFORE <date> (search key) .............................   52
+       SENTON <date> (search key) .................................   52
+       SENTSINCE <date> (search key) ..............................   52
+       SHOULD (specification requirement term) ....................    4
+       SHOULD NOT (specification requirement term) ................    4
+
+
+
+Crispin                     Standards Track                   [Page 105]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+       SINCE <date> (search key) ..................................   52
+       SMALLER <n> (search key) ...................................   52
+       STARTTLS (command) .........................................   27
+       STATUS (command) ...........................................   44
+       STATUS (response) ..........................................   70
+       STORE (command) ............................................   58
+       SUBJECT <string> (search key) ..............................   53
+       SUBSCRIBE (command) ........................................   38
+       Session Flag (class of flag) ...............................   12
+       System Flag (type of flag) .................................   11
+       TEXT (part specifier) ......................................   56
+       TEXT <string> (search key) .................................   53
+       TO <string> (search key) ...................................   53
+       TRYCREATE (response code) ..................................   65
+       UID (command) ..............................................   60
+       UID (fetch item) ...........................................   58
+       UID (fetch result) .........................................   79
+       UID <sequence set> (search key) ............................   53
+       UIDNEXT (response code) ....................................   65
+       UIDNEXT (status item) ......................................   45
+       UIDVALIDITY (response code) ................................   65
+       UIDVALIDITY (status item) ..................................   45
+       UNANSWERED (search key) ....................................   53
+       UNDELETED (search key) .....................................   53
+       UNDRAFT (search key) .......................................   53
+       UNFLAGGED (search key) .....................................   53
+       UNKEYWORD <flag> (search key) ..............................   53
+       UNSEEN (response code) .....................................   65
+       UNSEEN (search key) ........................................   53
+       UNSEEN (status item) .......................................   45
+       UNSUBSCRIBE (command) ......................................   39
+       Unique Identifier (UID) (message attribute) ................    8
+       X<atom> (command) ..........................................   62
+       [RFC-2822] Size (message attribute) ........................   12
+       \Answered (system flag) ....................................   11
+       \Deleted (system flag) .....................................   11
+       \Draft (system flag) .......................................   11
+       \Flagged (system flag) .....................................   11
+       \Marked (mailbox name attribute) ...........................   69
+       \Noinferiors (mailbox name attribute) ......................   69
+       \Noselect (mailbox name attribute) .........................   69
+       \Recent (system flag) ......................................   11
+       \Seen (system flag) ........................................   11
+       \Unmarked (mailbox name attribute) .........................   69
+
+
+
+
+
+
+
+Crispin                     Standards Track                   [Page 106]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+Author's Address
+
+   Mark R. Crispin
+   Networks and Distributed Computing
+   University of Washington
+   4545 15th Avenue NE
+   Seattle, WA  98105-4527
+
+   Phone: (206) 543-5762
+
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                   [Page 107]
+
+RFC 3501                         IMAPv4                       March 2003
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.  v This
+   document and the information contained herein is provided on an "AS
+   IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
+   FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
+   LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
+   NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
+   OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                   [Page 108]
+
+
diff --git a/imap/docs/rfc/rfc3502.txt b/imap/docs/rfc/rfc3502.txt
new file mode 100644
index 00000000..f6b61a44
--- /dev/null
+++ b/imap/docs/rfc/rfc3502.txt
@@ -0,0 +1,395 @@
+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 3502                      University of Washington
+Category: Standards Track                                     March 2003
+
+
+    Internet Message Access Protocol (IMAP) - MULTIAPPEND Extension
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+Abstract
+
+   This document describes the multiappending extension to the Internet
+   Message Access Protocol (IMAP) (RFC 3501).  This extension provides
+   substantial performance improvements for IMAP clients which upload
+   multiple messages at a time to a mailbox on the server.
+
+   A server which supports this extension indicates this with a
+   capability name of "MULTIAPPEND".
+
+Terminology
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
+   be interpreted as described in [KEYWORDS].
+
+Introduction
+
+   The MULTIAPPEND extension permits uploading of multiple messages with
+   a single command.  When used in conjunction with the [LITERAL+]
+   extension, the entire upload is accomplished in a single
+   command/response round trip.
+
+   A MULTIAPPEND APPEND operation is atomic; either all messages are
+   successfully appended, or no messages are appended.
+
+   In the base IMAP specification, each message must be appended in a
+   separate command, and there is no mechanism to "unappend" messages if
+   an error occurs while appending.  Also, some mail stores may require
+
+
+
+Crispin                     Standards Track                     [Page 1]
+
+RFC 3502                    IMAP MULTIAPPEND                  March 2003
+
+
+   an expensive "open/lock + sync/unlock/close" operation as part of
+   appending; this can be quite expensive if it must be done on a
+   per-message basis.
+
+   If the server supports both LITERAL+ and pipelining but not
+   MULTIAPPEND, it may be possible to get some of the performance
+   advantages of MULTIAPPEND by doing a pipelined "batch" append.
+   However, it will not work as well as MULTIAPPEND for the following
+   reasons:
+
+        1) Multiple APPEND commands, even as part of a pipelined batch,
+        are non-atomic by definition.  There is no way to revert the
+        mailbox to the state before the batch append in the event of an
+        error.
+
+        2) It may not be feasible for the server to coalesce pipelined
+        APPEND operations so as to avoid the "open/lock +
+        sync/unlock/close" overhead described above.  In any case, such
+        coalescing would be timing dependent and thus potentially
+        unreliable.  In particular, with traditional UNIX mailbox files,
+        it is assumed that a lock is held only for a single atomic
+        operation, and many applications disregard any lock that is
+        older than 5 minutes.
+
+        3) If an error occurs, depending upon the nature of the error,
+        it is possible for additional messages to be appended after the
+        error.  For example, the user wants to append 5 messages, but a
+        disk quota error occurs with the third message because of its
+        size.  However, the fourth and fifth messages have already been
+        sent in the pipeline, so the mailbox ends up with the first,
+        second, fourth, and fifth messages of the batch appended.
+
+6.3.11.  APPEND Command
+
+   Arguments:  mailbox name
+               one or more messages to upload, specified as:
+                  OPTIONAL flag parenthesized list
+                  OPTIONAL date/time string
+                  message literal
+
+   Data:       no specific responses for this command
+
+   Result:     OK - append completed
+               NO - append error: can't append to that mailbox, error
+                    in flags or date/time or message text,
+                    append cancelled
+               BAD - command unknown or arguments invalid
+
+
+
+
+Crispin                     Standards Track                     [Page 2]
+
+RFC 3502                    IMAP MULTIAPPEND                  March 2003
+
+
+      The APPEND command appends the literal arguments as new messages
+      to the end of the specified destination mailbox.  This argument
+      SHOULD be in the format of an [RFC-2822] message.  8-bit
+      characters are permitted in the message.  A server implementation
+      that is unable to preserve 8-bit data properly MUST be able to
+      reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB]
+      content transfer encoding.
+
+            Note: There MAY be exceptions, e.g., draft messages, in
+            which required [RFC-2822] header lines are omitted in the
+            message literal argument to APPEND.  The full implications
+            of doing so MUST be understood and carefully weighed.
+
+      If a flag parenthesized list is specified, the flags SHOULD be set
+      in the resulting message; otherwise, the flag list of the
+      resulting message is set empty by default.
+
+      If a date-time is specified, the internal date SHOULD be set in
+      the resulting message; otherwise, the internal date of the
+      resulting message is set to the current date and time by default.
+
+      A zero-length message literal argument is an error, and MUST
+      return a NO.  This can be used to cancel the append.
+
+      If the append is unsuccessful for any reason (including being
+      cancelled), the mailbox MUST be restored to its state before the
+      APPEND attempt; no partial appending is permitted.  The server MAY
+      return an error before processing all the message arguments.
+
+      If the destination mailbox does not exist, a server MUST return an
+      error, and MUST NOT automatically create the mailbox.  Unless it
+      is certain that the destination mailbox can not be created, the
+      server MUST send the response code "[TRYCREATE]" as the prefix of
+      the text of the tagged NO response.  This gives a hint to the
+      client that it can attempt a CREATE command and retry the APPEND
+      if the CREATE is successful.
+
+      If the mailbox is currently selected, the normal new message
+      actions SHOULD occur.  Specifically, the server SHOULD notify the
+      client immediately via an untagged EXISTS response.  If the server
+      does not do so, the client MAY issue a NOOP command (or failing
+      that, a CHECK command) after one or more APPEND commands.
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 3]
+
+RFC 3502                    IMAP MULTIAPPEND                  March 2003
+
+
+   Example: C: A003 APPEND saved-messages (\Seen) {329}
+            S: + Ready for literal data
+            C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+            C: From: Fred Foobar <foobar@Blurdybloop.example.COM>
+            C: Subject: afternoon meeting
+            C: To: mooch@owatagu.example.net
+            C: Message-Id: <B27397-0100000@Blurdybloop.example.COM>
+            C: MIME-Version: 1.0
+            C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+            C:
+            C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+            C:  (\Seen) " 7-Feb-1994 22:43:04 -0800" {295}
+            S: + Ready for literal data
+            C: Date: Mon, 7 Feb 1994 22:43:04 -0800 (PST)
+            C: From: Joe Mooch <mooch@OWaTaGu.example.net>
+            C: Subject: Re: afternoon meeting
+            C: To: foobar@blurdybloop.example.com
+            C: Message-Id: <a0434793874930@OWaTaGu.example.net>
+            C: MIME-Version: 1.0
+            C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+            C:
+            C: 3:30 is fine with me.
+            C:
+            S: A003 OK APPEND completed
+            C: A004 APPEND bogusname (\Flagged) {1023}
+            S: A004 NO [TRYCREATE] No such mailbox as bogusname
+            C: A005 APPEND test (\Flagged) {99}
+            S: + Ready for literal data
+            C: Date: Mon, 7 Feb 2000 22:43:04 -0800 (PST)
+            C: From: Fred Foobar <fred@example.com>
+            C: Subject: hmm...
+            C:  {35403}
+            S: A005 NO APPEND failed: Disk quota exceeded
+
+        Note: The APPEND command is not used for message delivery,
+        because it does not provide a mechanism to transfer [SMTP]
+        envelope information.
+
+Modification to IMAP4rev1 Base Protocol Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].
+
+   append          = "APPEND" SP mailbox 1*append-message
+
+   append-message  = [SP flag-list] [SP date-time] SP literal
+
+
+
+
+
+Crispin                     Standards Track                     [Page 4]
+
+RFC 3502                    IMAP MULTIAPPEND                  March 2003
+
+
+MULTIAPPEND Interaction with UIDPLUS Extension
+
+   Servers which support both MULTIAPPEND and [UIDPLUS] will have the
+   "resp-code-apnd" rule modified as follows:
+
+   resp-code-apnd  = "APPENDUID" SP nz-number SP set
+
+   That is, the APPENDUID response code returns as many UIDs as there
+   were messages appended in the multiple append.  The UIDs returned
+   should be in the order the articles where appended.  The message set
+   may not contain extraneous UIDs or the symbol "*".
+
+Security Considerations
+
+   The MULTIAPPEND extension does not raise any security considerations
+   that are not present in the base [IMAP] protocol, and these issues
+   are discussed in [IMAP].  Nevertheless, it is important to remember
+   that IMAP4rev1 protocol transactions, including electronic mail data,
+   are sent in the clear over the network unless protection from
+   snooping is negotiated, either by the use of STARTTLS, privacy
+   protection is negotiated in the AUTHENTICATE command, or some other
+   protection mechanism is in effect.
+
+Normative References
+
+   [ABNF]     Crocker, D. and P. Overell, "Augmented BNF for Syntax
+              Specifications: ABNF", RFC 2234, November 1997.
+
+   [IMAP]     Crispin, M., "Internet Message Access Protocol - Version
+              4rev1", RFC 3501, March 2003.
+
+   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [MIME-IMB] Freed, N. and N. Borenstein, "MIME (Multipurpose Internet
+              Mail Extensions) Part One: Format of Internet Message
+              Bodies", RFC 2045, November 1996.
+
+   [RFC-2822] Resnick, P., "Internet Message Format", RFC 2822, April
+              2001.
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 5]
+
+RFC 3502                    IMAP MULTIAPPEND                  March 2003
+
+
+Informative References
+
+   [LITERAL+] Myers, J., "IMAP4 non-synchronizing literals", RFC 2088,
+              January 1997.
+
+   [UIDPLUS]  Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June 1988.
+
+   [SMTP]     Klensin, J., Editor, "Simple Mail Transfer Protocol", RFC
+              2821, April 2001.
+
+Author's Address
+
+   Mark R. Crispin
+   Networks and Distributed Computing
+   University of Washington
+   4545 15th Avenue NE
+   Seattle, WA  98105-4527
+
+   Phone: (206) 543-5762
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 6]
+
+RFC 3502                    IMAP MULTIAPPEND                  March 2003
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 7]
+
diff --git a/imap/docs/rfc/rfc3503.txt b/imap/docs/rfc/rfc3503.txt
new file mode 100644
index 00000000..5b82fb08
--- /dev/null
+++ b/imap/docs/rfc/rfc3503.txt
@@ -0,0 +1,507 @@
+
+
+
+
+
+
+Network Working Group                                        A. Melnikov
+Request for Comments: 3503                 ACI Worldwide/MessagingDirect
+Category: Standards Track                                     March 2003
+
+
+          Message Disposition Notification (MDN) profile for
+                Internet Message Access Protocol (IMAP)
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+Abstract
+
+   The Message Disposition Notification (MDN) facility defined in RFC
+   2298 provides a means by which a message can request that message
+   processing by the recipient be acknowledged as well as a format to be
+   used for such acknowledgements.  However, it doesn't describe how
+   multiple Mail User Agents (MUAs) should handle the generation of MDNs
+   in an Internet Message Access Protocol (IMAP4) environment.
+
+   This document describes how to handle MDNs in such an environment and
+   provides guidelines for implementers of IMAP4 that want to add MDN
+   support to their products.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 1]
+
+RFC 3503                  MDN profile for IMAP                March 2003
+
+
+Table of Contents
+
+   1.  Conventions Used in this Document.............................  2
+   2.  Introduction and Overview.....................................  2
+   3.  Client behavior...............................................  3
+       3.1. Client behavior when receiving a message.................  5
+       3.2. Client behavior when copying a message...................  5
+       3.3. Client behavior when sending a message...................  5
+       3.4. Client behavior when saving a temporary message..........  5
+   4.  Server behavior...............................................  5
+       4.1. Server that supports arbitrary keywords..................  5
+       4.2. Server that supports only $MDNSent keyword...............  5
+       4.3. Interaction with IMAP ACL extension......................  6
+   5.  Examples......................................................  6
+   6.  Security Considerations.......................................  7
+   7.  Formal Syntax.................................................  7
+   8.  Acknowledgments...............................................  7
+   9.  Normative References..........................................  8
+   10. Author's Address..............................................  8
+   11. Full Copyright Statement......................................  9
+
+1.  Conventions Used in this Document
+
+   "C:" and "S:" in examples show lines sent by the client and server
+   respectively.
+
+   The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in
+   this document when typed in uppercase are to be interpreted as
+   defined in "Key words for use in RFCs to Indicate Requirement Levels"
+   [KEYWORDS].
+
+2.  Introduction and Overview
+
+   This memo defines an additional [IMAP4] mailbox keyword that allows
+   multiple Mail User Agents (MUAs) to know if a requested receipt
+   notification was sent.
+
+   Message Disposition Notification [MDN] does not require any special
+   support of IMAP in the case where a user has access to the mailstore
+   from only one computer and is using a single MUA.  In this case, the
+   MUA behaves as described in [MDN], i.e., the MUA performs automatic
+   processing and generates corresponding MDNs, it performs requested
+   action and, with the user's permission, sends appropriate MDNs.  The
+   MUA will not send MDN twice because the MUA keeps track of sent
+   notifications in a local configuration.  However, that does not work
+   when IMAP is used to access the same mailstore from different
+   locations or is using different MUAs.
+
+
+
+
+Melnikov                    Standards Track                     [Page 2]
+
+RFC 3503                  MDN profile for IMAP                March 2003
+
+
+   This document defines a new special purpose mailbox keyword $MDNSent
+   that must be used by MUAs.  It does not define any new command or
+   response for IMAP, but describes a technique that MUAs should use to
+   achieve interoperability.
+
+   When a client opens a mailbox for the first time, it verifies that
+   the server is capable of storing the $MDNSent keyword by examining
+   the PERMANENTFLAGS response code.  In order to support MDN in IMAP, a
+   server MUST support either the $MDNSent keyword, or arbitrary message
+   keywords.
+
+3.  Client behavior
+
+   The use of IMAP requires few additional steps in mail processing on
+   the client side.  The following timeline modifies the timeline found
+   in Section 4 of [MDN].
+
+   -- User composes message.
+
+   -- User tells MUA to send message.
+
+   -- MUA passes message to MSA (original recipient information passed
+      along).  MUA [optionally] saves message to a folder for sent mail
+      with $MDNSent flag set.
+
+   -- MSA sends message to MTA.
+
+   -- Final MTA receives message.
+
+   -- Final MTA delivers message to MUA (possibly generating DSN).
+
+   -- MUA logs into IMAP server, opens mailbox, verifies if mailbox can
+      store $MDNSent keyword by examining PERMANENTFLAGS response.
+
+   -- MUA performs automatic processing and generates corresponding MDNs
+      ("dispatched", "processed", "deleted", "denied" or "failed"
+      disposition type with "automatic-action" and "MDN-sent-
+      automatically" disposition modes) for messages that do not have
+      $MDNSent keyword, or \Draft flag set. (*)
+
+   -- MUA sets the $MDNSent keyword for every message that required an
+      automatic MDN to be sent, whether or not the MDN was sent.
+
+   -- MUA displays a list of messages to user.
+
+   -- User selects a message and requests that some action be performed
+      on it.
+
+
+
+
+Melnikov                    Standards Track                     [Page 3]
+
+RFC 3503                  MDN profile for IMAP                March 2003
+
+
+   -- MUA performs requested action and, with user's permission, sends
+      appropriate MDN ("displayed", "dispatched", "processed",
+      "deleted", "denied" or "failed" disposition type with "manual-
+      action" and "MDN-sent-manually" or "MDN-sent-automatically"
+      disposition mode).  If the generated MDN is saved to a mailbox
+      with the APPEND command, the client MUST specify the $MDNSent
+      keyword in the APPEND.
+
+   -- MUA sets the $MDNSent keyword for all messages for which the user
+      confirmed the dispatching of disposition (or was explicitly
+      prohibited to do so).
+
+   -- User possibly performs other actions on message, but no further
+      MDNs are generated.
+
+   (*) Note: MUA MUST NOT use \Recent flag as an indicator that it
+       should send MDN, because according to [IMAP4], "If multiple
+       connections have the same mailbox selected simultaneously, it is
+       undefined which of these connections will see newly-arrived
+       messages with \Recent set and which will see it without \Recent
+       set".  Thus, using \Recent as an indicator will cause
+       unpredictable client behavior with different IMAP4 servers.
+       However, the client MAY use \Seen flag as one of the indicators
+       that MDN must not be sent.  The client MUST NOT use any other
+       standard flags, like \Draft or \Answered, to indicate that MDN
+       was previously sent, because they have different well known
+       meaning.  In any case, in the presence of the $MDNSent keyword,
+       the client MUST ignore all other flags or keywords for the
+       purpose of generating an MDN and MUST NOT send the MDN.
+
+   When the client opens a mailbox for the first time, it must verify
+   that the server supports the $MDNSent keyword, or arbitrary message
+   keywords by examining PERMANENTFLAGS response code.
+
+   The client MUST NOT try to set the $MDNSent keyword if the server is
+   incapable of storing it permanently.
+
+   The client MUST be prepared to receive NO from the server as the
+   result of STORE $MDNSent when the server advertises the support of
+   storing arbitrary keywords, because the server may limit the number
+   of message keywords it can store in a particular mailbox.  A client
+   SHOULD NOT send MDN if it fails to store the $MDNSent keyword.
+
+   Once the $MDNSent keyword is set, it MUST NOT be unset by a client.
+   The client MAY set the $MDNSent keyword when a user denies sending
+   the notification.  This prohibits all other MUAs from sending MDN for
+   this message.
+
+
+
+
+Melnikov                    Standards Track                     [Page 4]
+
+RFC 3503                  MDN profile for IMAP                March 2003
+
+
+3.1.  Client behavior when receiving a message
+
+   The client MUST NOT send MDN if a message has the $MDNSent keyword
+   set.  It also MUST NOT send MDN if a message has \Draft flag, because
+   some clients use this flag to mark a message as incomplete.
+
+   See the timeline in section 3 for details on client behavior when
+   receiving a message.
+
+3.2.  Client behavior when copying a message
+
+   The client SHOULD verify that $MDNSent is preserved on a COPY
+   operation.  Furthermore, when a message is copied between servers
+   with the APPEND command, the client MUST set the $MDNSent keyword
+   correctly.
+
+3.3.  Client behavior when sending a message
+
+   When saving a sent message to any folder, the client MUST set the
+   $MDNSent keyword to prevent another client from sending MDN for the
+   message.
+
+3.4.  Client behavior when saving a temporary message
+
+   When saving an unfinished message to any folder client MUST set
+   $MDNSent keyword to prevent another client from sending MDN for the
+   message.
+
+4.  Server behavior
+
+   Server implementors that want to follow this specification must
+   insure that their server complies with either section 4.1 or section
+   4.2.  If the server also supports the IMAP [ACL] extension, it MUST
+   also comply with the section 4.3.
+
+4.1.  Server that supports arbitrary keywords
+
+   No changes are required from the server to make it compatible with
+   the extension described in this document if it supports arbitrary
+   keywords.
+
+4.2.  Server that supports only $MDNSent keyword
+
+   Servers that support only the $MDNSent keyword MUST preserve it on
+   the COPY operation.  It is also expected that a server that supports
+   SEARCH <flag> will also support the SEARCH KEYWORD $MDNSent.
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 5]
+
+RFC 3503                  MDN profile for IMAP                March 2003
+
+
+4.3.  Interaction with IMAP ACL extension
+
+   Any server that conforms to either 4.1 or 4.2 and also supports the
+   IMAP [ACL] extension, SHOULD preserve the $MDNSent keyword on COPY
+   even if the client does not have 'w' right.  This will prevent the
+   generation of a duplicated MDN for the same message.  Note that the
+   server MUST still check if the client has rights to perform the COPY
+   operation on a message according to [ACL].
+
+5.  Examples
+
+   1) MUA opens mailbox for the first time.
+
+   a) The server supports storing of arbitrary keywords
+
+   C: a100 select INBOX
+   S: * FLAGS (\Flagged \Draft \Deleted \Seen)
+   S: * OK [PERMANENTFLAGS (\Flagged \Draft \Deleted \Seen \*)]
+   S: * 5 EXISTS
+   S: * 3 RECENT
+   S: * OK [UIDVALIDITY 894294713]
+   S: a100 OK [READ-WRITE] Completed
+
+   b) The server supports storing of the $MDNSent keyword
+
+   C: a100 select INBOX
+   S: * FLAGS (\Flagged \Draft \Deleted \Seen $MDNSent)
+   S: * OK [PERMANENTFLAGS (\Flagged \Draft \Deleted \Seen $MDNSent)]
+   S: * 5 EXISTS
+   S: * 3 RECENT
+   S: * OK [UIDVALIDITY 894294713]
+   S: a100 OK [READ-WRITE] Completed
+
+   2) The MUA successfully sets the $MDNSent keyword
+
+   C: a200 STORE 4 +FLAGS ($MDNSent)
+   S: * 4 FETCH (FLAGS (\Flagged \Seen $MDNSent))
+   S: * FLAGS ($MDNSent \Flagged \Deleted \Draft \Seen)
+   S: * OK [PERMANENTFLAGS ($MDNSent \Flagged \Deleted \Draft \Seen \*)]
+   S: a200 OK STORE completed
+
+   3) The server refuses to store the $MDNSent keyword
+
+   C: a200 STORE 4 +FLAGS ($MDNSent)
+   S: a200 NO STORE failed : no space left to store $MDNSent keyword
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 6]
+
+RFC 3503                  MDN profile for IMAP                March 2003
+
+
+   4) All clients and servers MUST treat the $MDNSent keyword as case
+   insensitive in all operations, as stated in [IMAP].
+
+   C: a300 FETCH 1:* FLAGS
+   S: * 1 FETCH (FLAGS (\Seen))
+   S: * 2 FETCH (FLAGS (\Answered \Seen $MdnSENt))
+   S: * 3 FETCH (FLAGS ())
+   S: * 4 FETCH (FLAGS (\Flagged \Seen $MdnSENT))
+   S: * 5 FETCH (FLAGS ($MDNSent))
+   S: * 6 FETCH (FLAGS (\Recent))
+   S: a300 OK FETCH completed
+   C: a400 SEARCH KEYWORDS $mdnsent
+   S: * SEARCH 2 4 5
+   S: a400 OK SEARCH completed
+
+6.  Security Considerations
+
+   There are no known security issues with this extension, not found in
+   [MDN] and/or [IMAP4].
+
+   Section 4.3 changes ACL checking requirements on an IMAP server that
+   implements IMAP [ACL] extension.
+
+7.  Formal Syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (BNF) notation as specified in [RFC-822], as modified by
+   [IMAP4].  Non-terminals referenced, but not defined below, are as
+   defined by [IMAP4].
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper or lower case characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+   flag_keyword    ::= "$MDNSent" / other_keywords
+
+   other_keywords  ::= atom
+
+8.  Acknowledgments
+
+   This document is the product of discussions that took place on the
+   IMAP mailing list.  Special gratitude to Cyrus Daboo and Randall
+   Gellens for reviewing the document.
+
+   Thank you to my father who as he has helped to make me what I am.  I
+   miss you terribly.
+
+
+
+
+Melnikov                    Standards Track                     [Page 7]
+
+RFC 3503                  MDN profile for IMAP                March 2003
+
+
+9.  Normative References
+
+   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [MDN]      Fajman, R., "An Extensible Message Format for Message
+              Disposition Notifications", RFC 2298, March 1998.
+
+   [IMAP4]    Crispin, M., "Internet Message Access Protocol - Version
+              4rev1", RFC 3501, March 2003.
+
+   [ACL]      Myers, J., "IMAP4 ACL extension", RFC 2086, January 1997.
+
+10.  Author's Address
+
+   Alexey Melnikov
+   ACI Worldwide/MessagingDirect
+   59 Clarendon Road
+   Watford, Hertfordshire
+   United Kingdom, WD17 1FQ
+
+   Phone: +44 1923 81 2877
+   EMail: mel@messagingdirect.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 8]
+
+RFC 3503                  MDN profile for IMAP                March 2003
+
+
+11.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 9]
+
diff --git a/imap/docs/rfc/rfc3516.txt b/imap/docs/rfc/rfc3516.txt
new file mode 100644
index 00000000..4d021975
--- /dev/null
+++ b/imap/docs/rfc/rfc3516.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group                                       L. Nerenberg
+Request for Comments: 3516                               Orthanc Systems
+Category: Standards Track                                     April 2003
+
+
+                     IMAP4 Binary Content Extension
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+Abstract
+
+   This memo defines the Binary extension to the Internet Message Access
+   Protocol (IMAP4).  It provides a mechanism for IMAP4 clients and
+   servers to exchange message body data without using a MIME content-
+   transfer-encoding.
+
+1.   Conventions Used in this Document
+
+   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+   in this document are to be interpreted as described in [KEYWORD].
+
+   The abbreviation "CTE" means content-transfer-encoding.
+
+2.   Introduction
+
+   The MIME extensions to Internet messaging allow for the transmission
+   of non-textual (binary) message content [MIME-IMB].  Since the
+   traditional transports for messaging are not always capable of
+   passing binary data transparently, MIME provides encoding schemes
+   that allow binary content to be transmitted over transports that are
+   not otherwise able to do so.
+
+   The overhead of MIME-encoding this content can be considerable in
+   some contexts (e.g., slow radio links, streaming multimedia).
+   Reducing the overhead associated with CTE schemes such as base64
+
+
+
+
+
+
+Nerenberg                   Standards Track                     [Page 1]
+
+RFC 3516             IMAP4 Binary Content Extension           April 2003
+
+
+   can give a noticeable reduction in resource consumption.  The Binary
+   extension lets the server perform CTE decoding prior to transmitting
+   message data to the client.
+
+3.  Content-Transfer-Encoding Considerations
+
+   Every IMAP4 body section has a MIME content-transfer-encoding.
+   (Those without an explicit Content-Transfer-Encoding header are
+   implicitly labeled as "7bit" content.)  In the terminology of [MIME-
+   IMB], the CTE specifies both a decoding algorithm and the domain of
+   the decoded data.  In this memo, "decoding" refers to the CTE
+   decoding step described in [MIME-IMB].
+
+   Certain CTEs use an identity encoding transformation.  For these CTEs
+   there is no decoding required, however the domain of the underlying
+   data may not be expressible in the IMAP4 protocol (e.g., MIME
+   "binary" content containing NUL octets).  To accommodate these cases
+   the Binary extension introduces a new type of literal protocol
+   element that is fully eight bit transparent.
+
+   Thus, server  processing of the FETCH BINARY command involves two
+   logical steps:
+
+   1)  perform any CTE-related decoding
+
+   2)  determine the domain of the decoded data
+
+   Step 2 is necessary to determine which protocol element should be
+   used to transmit the decoded data.  (See FETCH Response Extensions
+   for further details.)
+
+4.  Framework for the IMAP4 Binary Extension
+
+   This memo defines the following extensions to [IMAP4rev1].
+
+4.1.  CAPABILITY Identification
+
+   IMAP4 servers that support this extension MUST include "BINARY" in
+   the response list to the CAPABILITY command.
+
+4.2.  FETCH Command Extensions
+
+   This extension defines three new FETCH command data items.
+
+      BINARY<section-binary>[<partial>]
+
+         Requests that the specified section be transmitted after
+         performing CTE-related decoding.
+
+
+
+Nerenberg                   Standards Track                     [Page 2]
+
+RFC 3516             IMAP4 Binary Content Extension           April 2003
+
+
+         The <partial> argument, if present, requests that a subset of
+         the data be returned.  The semantics of a partial FETCH BINARY
+         command are the same as for a partial FETCH BODY command, with
+         the exception that the <partial> arguments refer to the DECODED
+         section data.
+
+      BINARY.PEEK<section-binary>[<partial>]
+
+         An alternate form of FETCH BINARY that does not implicitly set
+         the \Seen flag.
+
+      BINARY.SIZE<section-binary>
+
+         Requests the decoded size of the section (i.e., the size to
+         expect in response to the corresponding FETCH BINARY request).
+
+         Note: client authors are cautioned that this might be an
+         expensive operation for some server implementations.
+         Needlessly issuing this request could result in degraded
+         performance due to servers having to calculate the value every
+         time the request is issued.
+
+4.3.  FETCH Response Extensions
+
+   This extension defines two new FETCH response data items.
+
+      BINARY<section-binary>[<<number>>]
+
+         An <nstring> or <literal8> expressing the content of the
+         specified section after removing any CTE-related encoding.  If
+         <number> is present it refers to the offset within the DECODED
+         section data.
+
+         If the domain of the decoded data is "8bit" and the data does
+         not contain the NUL octet, the server SHOULD return the data in
+         a <string> instead of a <literal8>; this allows the client to
+         determine if the "8bit" data contains the NUL octet without
+         having to explicitly scan the data stream for for NULs.
+
+         If the server does not know how to decode the section's CTE, it
+         MUST fail the request and issue a "NO" response that contains
+         the "UNKNOWN-CTE" extended response code.
+
+
+
+
+
+
+
+
+
+Nerenberg                   Standards Track                     [Page 3]
+
+RFC 3516             IMAP4 Binary Content Extension           April 2003
+
+
+      BINARY.SIZE<section-binary>
+
+         The size of the section after removing any CTE-related
+         encoding.  The value returned MUST match the size of the
+         <nstring> or <literal8> that will be returned by the
+         corresponding FETCH BINARY request.
+
+         If the server does not know how to decode the section's CTE, it
+         MUST fail the request and issue a "NO" response that contains
+         the "UNKNOWN-CTE" extended response code.
+
+4.4.  APPEND Command Extensions
+
+   The APPEND command is extended to allow the client to append data
+   containing NULs by using the <literal8> syntax.  The server MAY
+   modify the CTE of the appended data, however any such transformation
+   MUST NOT result in a loss of data.
+
+   If the destination mailbox does not support the storage of binary
+   content, the server MUST fail the request and issue a "NO" response
+   that contains the "UNKNOWN-CTE" extended response code.
+
+5.  MIME Encoded Headers
+
+   [MIME-MHE] defines an encoding that allows for non-US-ASCII text in
+   message headers.  This encoding is not the same as the content-
+   transfer-encoding applied to message bodies, and the decoding
+   transformations described in this memo do not apply to [MIME-MHE]
+   encoded header text.  A server MUST NOT perform any conversion of
+   [MIME-MHE] encoded header text in response to any binary FETCH or
+   APPEND request.
+
+6.  Implementation Considerations
+
+   Messaging clients and servers have been notoriously lax in their
+   adherence to the Internet CRLF convention for terminating lines of
+   textual data in Internet protocols.  When sending data using the
+   Binary extension, servers MUST ensure that textual line-oriented
+   sections are always transmitted using the IMAP4 CRLF line termination
+   syntax, regardless of the underlying storage representation of the
+   data on the server.
+
+   A server may choose to store message body binary content in a non-
+   encoded format.  Regardless of the internal storage representation
+   used, the server MUST issue BODYSTRUCTURE responses that describe the
+   message as though the binary-encoded sections are encoded in a CTE
+
+
+
+
+
+Nerenberg                   Standards Track                     [Page 4]
+
+RFC 3516             IMAP4 Binary Content Extension           April 2003
+
+
+   acceptable to the IMAP4 base specification.  Furthermore, the results
+   of a FETCH BODY MUST return the message body content in the format
+   described by the corresponding FETCH BODYSTRUCTURE response.
+
+   While the server is allowed to modify the CTE of APPENDed <literal8>
+   data, this should only be done when it is absolutely necessary.
+   Gratuitous encoding changes will render useless most cryptographic
+   operations that have been performed on the message.
+
+   This extension provides an optimization that is useful in certain
+   specific situations.  It does not absolve clients from providing
+   basic functionality (content transfer decoding) that should be
+   available in all messaging clients.  Clients supporting this
+   extension SHOULD be prepared to perform their own CTE decoding
+   operations.
+
+7.  Formal Protocol Syntax
+
+   The following syntax specification uses the augmented Backus-Naur
+   Form (ABNF) notation as used in [ABNF], and incorporates by reference
+   the Core Rules defined in that document.
+
+   This syntax augments the grammar specified in [IMAP4rev1].
+
+   append         =/  "APPEND" SP mailbox [SP flag-list]
+                      [SP date-time] SP literal8
+
+   fetch-att      =/  "BINARY" [".PEEK"] section-binary [partial]
+                      / "BINARY.SIZE" section-binary
+
+   literal8       =   "~{" number "}" CRLF *OCTET
+                      ; <number> represents the number of OCTETs
+                      ; in the response string.
+
+   msg-att-static =/  "BINARY" section-binary SP (nstring / literal8)
+                      / "BINARY.SIZE" section-binary SP number
+
+   partial        =   "<" number "." nz-number ">"
+
+   resp-text-code =/  "UNKNOWN-CTE"
+
+   section-binary =   "[" [section-part] "]"
+
+
+
+
+
+
+
+
+
+Nerenberg                   Standards Track                     [Page 5]
+
+RFC 3516             IMAP4 Binary Content Extension           April 2003
+
+
+8.  Normative References
+
+   [ABNF]      Crocker, D., Editor, and P. Overell, "Augmented BNF for
+               Syntax Specifications: ABNF", RFC 2234, November 1997.
+
+   [IMAP4rev1] Crispin, M., "Internet Message Access Protocol Version
+               4rev1", RFC 3501, March 2003.
+
+   [KEYWORD]   Bradner, S., "Key words for use in RFCs to Indicate
+               Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [MIME-IMB]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+               Extensions (MIME) Part One: Format of Internet Message
+               Bodies", RFC 2045, November 1996.
+
+   [MIME-MHE]  Moore, K., "MIME (Multipurpose Internet Mail Extensions)
+               Part Three: Message Header Extensions for Non-ASCII
+               Text", RFC 2047, November 1996.
+
+9.  Security Considerations
+
+   There are no known additional security issues with this extension
+   beyond those described in the base protocol described in [IMAP4rev1].
+
+10.  Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   intellectual property or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; neither does it represent that it
+   has made any effort to identify any such rights.  Information on the
+   IETF's procedures with respect to rights in standards-track and
+   standards-related documentation can be found in BCP-11.  Copies of
+   claims of rights made available for publication and any assurances of
+   licenses to be made available, or the result of an attempt made to
+   obtain a general license or permission for the use of such
+   proprietary rights by implementors or users of this specification can
+   be obtained from the IETF Secretariat.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights which may cover technology that may be required to practice
+   this standard.  Please address the information to the IETF Executive
+   Director.
+
+
+
+
+
+
+Nerenberg                   Standards Track                     [Page 6]
+
+RFC 3516             IMAP4 Binary Content Extension           April 2003
+
+
+11.  Author's Address
+
+   Lyndon Nerenberg
+   Orthanc Systems
+   1606 - 10770 Winterburn Road
+   Edmonton, Alberta
+   Canada  T5S 1T6
+
+   EMail: lyndon@orthanc.ab.ca
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Nerenberg                   Standards Track                     [Page 7]
+
+RFC 3516             IMAP4 Binary Content Extension           April 2003
+
+
+12.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Nerenberg                   Standards Track                     [Page 8]
+
diff --git a/imap/docs/rfc/rfc3656.txt b/imap/docs/rfc/rfc3656.txt
new file mode 100644
index 00000000..6c0ab5b1
--- /dev/null
+++ b/imap/docs/rfc/rfc3656.txt
@@ -0,0 +1,1067 @@
+
+
+
+
+
+
+Network Working Group                                      R. Siemborski
+Request for Comments: 3656                    Carnegie Mellon University
+Category: Experimental                                     December 2003
+
+
+                     The Mailbox Update (MUPDATE)
+                 Distributed Mailbox Database Protocol
+
+Status of this Memo
+
+   This memo defines an Experimental Protocol for the Internet
+   community.  It does not specify an Internet standard of any kind.
+   Discussion and suggestions for improvement are requested.
+   Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+Abstract
+
+   As the demand for high-performance mail delivery agents increases, it
+   becomes apparent that single-machine solutions are inadequate to the
+   task, both because of capacity limits and that the failure of the
+   single machine means a loss of mail delivery for all users.  It is
+   preferable to allow many machines to share the responsibility of mail
+   delivery.
+
+   The Mailbox Update (MUPDATE) protocol allows a group of Internet
+   Message Access Protocol (IMAP) or Post Office Protocol - Version 3
+   (POP3) servers to function with a unified mailbox namespace.  This
+   document is intended to serve as a reference guide to that protocol.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                      [Page 1]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+Table of Contents
+
+   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
+   2.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   3
+       2.1.  Atoms . . . . . . . . . . . . . . . . . . . . . . . . .   4
+       2.2.  Strings . . . . . . . . . . . . . . . . . . . . . . . .   4
+   3.  Server Responses  . . . . . . . . . . . . . . . . . . . . . .   4
+       3.1.  Response: OK  . . . . . . . . . . . . . . . . . . . . .   5
+       3.2.  Response: NO  . . . . . . . . . . . . . . . . . . . . .   5
+       3.3.  Response: BAD . . . . . . . . . . . . . . . . . . . . .   5
+       3.4.  Response: BYE . . . . . . . . . . . . . . . . . . . . .   6
+       3.5.  Response: RESERVE . . . . . . . . . . . . . . . . . . .   6
+       3.6.  Response: MAILBOX . . . . . . . . . . . . . . . . . . .   6
+       3.7.  Response: DELETE  . . . . . . . . . . . . . . . . . . .   7
+       3.8.  Server Capability Response. . . . . . . . . . . . . . .   7
+   4.  Client Commands . . . . . . . . . . . . . . . . . . . . . . .   8
+       4.1.  Command: ACTIVATE . . . . . . . . . . . . . . . . . . .   8
+       4.2.  Command: AUTHENTICATE . . . . . . . . . . . . . . . . .   8
+       4.3.  Command: DEACTIVATE . . . . . . . . . . . . . . . . . .   9
+       4.4.  Command: DELETE . . . . . . . . . . . . . . . . . . . .   9
+       4.5.  Command: FIND . . . . . . . . . . . . . . . . . . . . .   9
+       4.6.  Command: LIST . . . . . . . . . . . . . . . . . . . . .  10
+       4.7.  Command: LOGOUT . . . . . . . . . . . . . . . . . . . .  10
+       4.8.  Command: NOOP . . . . . . . . . . . . . . . . . . . . .  10
+       4.9.  Command: RESERVE. . . . . . . . . . . . . . . . . . . .  10
+       4.10. Command: STARTTLS . . . . . . . . . . . . . . . . . . .  11
+       4.11. Command: UPDATE . . . . . . . . . . . . . . . . . . . .  12
+   5.  MUPDATE Formal Syntax . . . . . . . . . . . . . . . . . . . .  12
+   6.  MUPDATE URL Scheme. . . . . . . . . . . . . . . . . . . . . .  14
+       6.1.  MUPDATE URL Scheme Registration Form. . . . . . . . . .  14
+   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
+   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
+   9.  Intellectual Property Rights. . . . . . . . . . . . . . . . .  16
+   10. References. . . . . . . . . . . . . . . . . . . . . . . . . .  17
+       10.1. Normative References. . . . . . . . . . . . . . . . . .  17
+       10.2. Informative References. . . . . . . . . . . . . . . . .  17
+   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  18
+   12. Author's Address. . . . . . . . . . . . . . . . . . . . . . .  18
+   13. Full Copyright Statement. . . . . . . . . . . . . . . . . . .  19
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                      [Page 2]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+1.  Introduction
+
+   In order to support an architecture where there are multiple [IMAP,
+   POP3] servers sharing a common mailbox database, it is necessary to
+   be able to provide atomic mailbox operations, as well as offer
+   sufficient guarantees about database consistency.
+
+   The primary goal of the MUPDATE protocol is to be simple to implement
+   yet allow for database consistency between participants.
+
+   The key words "MUST, "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
+   "RECOMMENDED", and "MAY" in this document are to be interpreted as
+   defined in BCP 14, RFC 2119 [KEYWORDS].
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.
+
+2.  Protocol Overview
+
+   The MUPDATE protocol assumes a reliable data stream such as a TCP
+   network connection.  IANA has registered port 3905 with a short name
+   of "mupdate" for this purpose.
+
+   In the current implementation of the MUPDATE protocol there are three
+   types of participants: a single master server, slave (or replica)
+   servers, and clients.  The master server maintains an authoritative
+   copy of the mailbox database.  Slave servers connect to the MUPDATE
+   master server as clients, and function as replicas from the point of
+   view of end clients.  End clients may connect to either the master or
+   any slave and perform searches against the database, however
+   operations that change the database can only be performed against the
+   master.  For the purposes of protocol discussion we will consider a
+   slave's connection to the master identical to that of any other
+   client.
+
+   After connection, all commands from a client to server must have an
+   associated unique tag which is an alphanumeric string.  Commands MAY
+   be pipelined from the client to the server (that is, the client need
+   not wait for the response before sending the next command).  The
+   server MUST execute the commands in the order they were received,
+   however.
+
+   If the server supports an inactivity login timeout, it MUST be at
+   least 15 minutes.
+
+
+
+
+
+
+
+Siemborski                    Experimental                      [Page 3]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+   MUPDATE uses data formats similar to those used in [ACAP].  That is,
+   atoms and strings.  All commands and tags in the protocol are
+   transmitted as atoms.  All other data is considered to a string, and
+   must be quoted or transmitted as a literal.
+
+   Outside of a literal, both clients and servers MUST support line
+   lengths of at least 1024 octets (including the trailing CR and LF
+   characters).  If a line of a longer length must be transmitted,
+   implementations MUST make use of literals to do so.
+
+2.1.  Atoms
+
+   An atom consists of one or more alphanumeric characters.  Atoms MUST
+   be less than 15 octets in length.
+
+2.2.  Strings
+
+   As in [ACAP], a string may be either literal or a quoted string.  A
+   literal is a sequence of zero or more octets (including CR and LF),
+   prefix-quoted with an octet count in the form of an open brace ("{"),
+   the number of octets, an optional plus sign to indicate that the data
+   follows immediately (a non-synchronized literal), a close brace
+   ("}"), and a CRLF sequence.  If the plus sign is omitted (a
+   synchronized literal), then the receiving side MUST send a "+ go
+   ahead" response, and the sending side MUST wait for this response.
+   Servers MUST support literals of atleast 4096 octets.
+
+   Strings that are sent from server to client SHOULD NOT be in the
+   synchronized literal format.
+
+   A quoted string is a sequence of zero or more 7-bit characters,
+   excluding CR, LF, and the double quote (<">), with double quote
+   characters at each end.
+
+   The empty string is represented as either "" (a quoted string with
+   zero characters between double quotes) or as {0} followed by CRLF (a
+   literal with an octet count of 0).
+
+3.  Server Responses
+
+   Every client command in the MUPDATE protocol may receive one or more
+   tagged responses from the server.  Each response is preceded by the
+   same tag as the command that elicited the response from the server.
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                      [Page 4]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+3.1.  Response: OK
+
+   A tagged OK response indicates that the operation completed
+   successfully.  There is a mandatory implementation-defined string
+   after the OK response.  This response also indicates the beginning of
+   the streaming update mode when given in response to an UPDATE
+   command.
+
+   Example:
+
+C: N01 NOOP
+S: N01 OK "NOOP Complete"
+
+3.2.  Response: NO
+
+   A tagged NO response indicates that the operation was explicitly
+   denied by the server or otherwise failed.  There is a mandatory
+   implementation-defined string after the NO response that SHOULD
+   explain the reason for denial.
+
+   Example:
+
+C: A01 AUTHENTICATE "PLAIN"
+S: A01 NO "PLAIN is not a supported SASL mechanism"
+
+3.3.  Response: BAD
+
+   A tagged BAD response indicates that the command from the client
+   could not be parsed or understood.  There is a mandatory
+   implementation-defined string after the BAD response to provide
+   additional information about the error.  Note that untagged BAD
+   responses are allowed if it is unclear what the tag for a given
+   command is (for example, if a blank line is received by the mupdate
+   server, it can generate an untagged BAD response).  In the case of an
+   untagged response, the tag should be replaced with a "*".
+
+   Example:
+
+C: C01 SELECT "INBOX"
+S: C01 BAD "This is not an IMAP server"
+C:
+S: * BAD "Need Command"
+
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                      [Page 5]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+3.4.  Response: BYE
+
+   A tagged BYE response indicates that the server has decided to close
+   the connection.  There is a mandatory implementation-defined string
+   after the BYE response that SHOULD explain the reason for closing the
+   connection.  The server MUST close the connection immediately after
+   transmitting the BYE response.
+
+   Example:
+
+C: L01 LOGOUT
+S: L01 BYE "User Logged Out"
+
+3.5.  Response: RESERVE
+
+   A tagged RESERVE response may only be given in response to a FIND,
+   LIST, or UPDATE command.  It includes two parameters: the name of the
+   mailbox that is being reserved (in mUTF-7 encoding, as specified in
+   [IMAP]) and a location string whose contents is defined by the
+   clients that are using the database, though it is RECOMMENDED that
+   the format of this string be the hostname of the server which is
+   storing the mailbox.
+
+   This response indicates that the given name is no longer available in
+   the namespace, though it does not indicate that the given mailbox is
+   available to clients at the current time.
+
+   Example:
+
+S: U01 RESERVE "internet.bugtraq" "mail2.example.org"
+
+3.6.  Response: MAILBOX
+
+   A tagged MAILBOX response may only be given in response to a FIND,
+   LIST, or UPDATE command.  It includes three parameters: the name of
+   the mailbox, a location string (as with RESERVE), and a client-
+   defined string that specifies the IMAP ACL [IMAP-ACL] of the mailbox.
+   This message indicates that the given mailbox is ready to be accessed
+   by clients.
+
+   Example:
+
+S: U01 MAILBOX "internet.bugtraq" "mail2.example.org" "anyone rls"
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                      [Page 6]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+3.7.  Response: DELETE
+
+   A tagged DELETE response may only be given in response to an UPDATE
+   command, and MUST NOT be given before the OK response to the UPDATE
+   command is given.  It contains a single parameter, that of the
+   mailbox that should be deleted from the slave's database.  This
+   response indicates that the given mailbox no longer exists in the
+   namespace of the database, and may be given for any mailbox name,
+   active, reserved, or nonexistent.  (Though implementations SHOULD NOT
+   issue DELETE responses for nonexistent mailboxes).
+
+   Example:
+
+S: U01 DELETE "user.rjs3.sent-mail-jan-2002"
+
+3.8.  Server Capability Response
+
+   Upon connection of the client to the server, and directly following a
+   successful STARTTLS command, the server MUST issue a capabilities
+   banner, of the following format:
+
+   The banner MUST contain a line that begins with "* AUTH" and contain
+   a space-separated list of SASL mechanisms that the server will accept
+   for authentication.  The mechanism names are transmitted as atoms.
+   Servers MAY advertise no available mechanisms (to indicate that
+   STARTTLS must be completed before authentication may occur).  If
+   STARTTLS is not supported by the server, then the line MUST contain
+   at least one mechanism.
+
+   If the banner is being issued without a TLS layer, and the server
+   supports the STARTTLS command, the banner MUST contain the line "*
+   STARTTLS".  If the banner is being issued under a TLS layer (or the
+   server does not support STARTTLS), the banner MUST NOT contain this
+   line.
+
+   The last line of the banner MUST start with "* OK MUPDATE" and be
+   followed by four strings: the server's hostname, an implementation-
+   defined string giving the name of the implementation, an
+   implementation-defined string giving the version of the
+   implementation, and a string that indicates if the server is a master
+   or a slave.  The master/slave indication MUST be either "(master)" or
+   an MUPDATE URL that defines where the master can be contacted.
+
+   Any unrecognized responses before the "* OK MUPDATE" response MUST be
+   ignored by the client.
+
+
+
+
+
+
+Siemborski                    Experimental                      [Page 7]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+   Example:
+
+S: * AUTH KERBEROS_V4 GSSAPI
+S: * STARTTLS
+S: * OK MUPDATE "mupdate.example.org" "Cyrus" "v2.1.2" "(master)"
+
+4.  Client Commands
+
+   The following are valid commands that a client may send to the
+   MUPDATE server: AUTHENTICATE, ACTIVATE, DEACTIVATE, DELETE, FIND,
+   LIST, LOGOUT, NOOP, RESERVE, STARTTLS, and UPDATE.
+
+   Before a successful AUTHENTICATE command has occurred, the server
+   MUST NOT accept any commands except for AUTHENTICATE, STARTTLS, and
+   LOGOUT (and SHOULD reply with a NO response for all other commands).
+
+4.1.  Command: ACTIVATE
+
+   The ACTIVATE command has 3 parameters: the mailbox name, its
+   location, and its ACL.  This command MUST NOT not be issued to a
+   slave server.
+
+   This command can also be used to update the ACL or location
+   information of a mailbox.  Note that it is not a requirement for a
+   mailbox to be reserved (or even exist in the database) for an
+   ACTIVATE command to succeed, implementations MUST allow this behavior
+   as it facilitates synchronization of the database with the current
+   state of the mailboxes.
+
+4.2.  Command: AUTHENTICATE
+
+   The AUTHENTICATE command initiates a [SASL] negotiation session
+   between the client and the server.  It has two parameters.  The first
+   parameter is mandatory, and is a string indicating the desired [SASL]
+   mechanism.  The second is a string containing an optional BASE64
+   encoded (as defined in section 6.8 of [MIME]) client first send.
+
+   All of the remaining SASL blobs that are sent MUST be sent across the
+   wire must be in BASE64 encoded format, and followed by a CR and LF
+   combination.  They MUST NOT be encoded as strings.
+
+   Clients may cancel authentication by sending a * followed by a CR and
+   LF.
+
+   The [SASL] service name for the MUPDATE protocol is "mupdate".
+   Implementations are REQUIRED to implement the GSSAPI [SASL]
+   mechanism, though they SHOULD implement as many mechanisms as
+   possible.
+
+
+
+Siemborski                    Experimental                      [Page 8]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+   If a security layer is negotiated, it should be used directly
+   following the CR and LF combination at the end of the server's OK
+   response (i.e., beginning with the client's next command) Only one
+   successful AUTHENTICATE command may be issued per session.
+
+4.3.  Command: DEACTIVATE
+
+   The DEACTIVATE command takes two parameters, the mailbox name and
+   location data.  The mailbox MUST already exist and be activated on
+   the MUPDATE server.  If the server responds OK, then the mailbox name
+   has been moved to the RESERVE state.  If the server responds NO, then
+   the mailbox name has not been moved (for example, the mailbox was not
+   already active).  Any ACL information that is known about the mailbox
+   MAY be lost when a DEACTIVATE succeeds.  This command MUST NOT be
+   issued to a slave.
+
+   Example:
+
+C: A01 DEACTIVATE "user.rjs3.new" "mail3.example.org!u4"
+S: A01 OK "Mailbox Reserved."
+
+4.4.  Command: DELETE
+
+   The DELETE command takes only a single parameter, the mailbox name to
+   be removed from the database's namespace.  The server SHOULD give a
+   NO response if the mailbox does not exist.  This command MUST NOT be
+   issued to a slave server.
+
+4.5.  Command: FIND
+
+   The FIND command takes a single parameter, a mailbox name.  The
+   server then responds with the current record for the given mailbox,
+   if any, and an OK response.
+
+   Example (mailbox does not exist):
+
+C: F01 FIND "user.rjs3.xyzzy"
+S: F01 OK "Search Complete"
+
+   Example (mailbox is reserved):
+
+C: F01 FIND "user.rjs3"
+S: F01 RESERVE "user.rjs3" "mail4.example.org"
+S: F01 OK "Search Complete"
+
+
+
+
+
+
+
+Siemborski                    Experimental                      [Page 9]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+4.6.  Command: LIST
+
+   The LIST command is similar to running FIND across the entire
+   database.  The LIST command takes a single optional parameter, which
+   is a prefix to try to match against the location field of the
+   records.  Without the parameter, LIST returns every record in the
+   database.
+
+   For each mailbox that matches, either a MAILBOX or a RESERVE response
+   (as applicable) is sent to the client.  When all responses are
+   complete, an OK response is issued.
+
+   Example:
+
+C: L01 LIST
+S: L01 RESERVE "user.rjs3" "mail4.example.org!u2"
+S: L01 MAILBOX "user.leg" "mail2.example.org!u1" "leg lrswipcda"
+S: L01 OK "List Complete"
+C: L02 LIST "mail4.example.org!"
+S: L02 RESERVE "user.rjs3" "mail4.example.org!u2"
+S: L02 OK "List Complete"
+
+4.7.  Command: LOGOUT
+
+   The LOGOUT command tells the server to close the connection.  Its
+   only valid response is the BYE response.  The LOGOUT command takes no
+   parameters.
+
+4.8.  Command: NOOP
+
+   The NOOP command takes no parameters.  Provided the client is
+   authenticated, its only acceptable response is an OK.  Any idle
+   timeouts that the server may have on the connection SHOULD be reset
+   upon receipt of this command.
+
+   If this command is issued after an UPDATE command has been issued,
+   then the OK response also indicates that all pending database updates
+   have been sent to the client.  That is, the slave can guarantee that
+   its local database is up to date as of a certain time by issuing a
+   NOOP and waiting for the OK.  The OK MUST NOT return until all
+   updates that were pending at the time of the NOOP have been sent.
+
+4.9.  Command: RESERVE
+
+   The RESERVE command takes two parameters (just like the RESERVE
+   response), the mailbox name to reserve and location data.  If the
+   server responds OK, then the mailbox name has been reserved.  If the
+   server responds NO, then the mailbox name has not been reserved (for
+
+
+
+Siemborski                    Experimental                     [Page 10]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+   example, another server has reserved it already).  This command MUST
+   NOT be issued to a slave.
+
+   The typical sequence for mailbox creation is:
+
+C: R01 RESERVE "user.rjs3.new" "mail3.example.org!u4"
+S: R01 OK "Mailbox Reserved."
+<client does local mailbox create operations>
+C: A01 ACTIVATE "user.rjs3.new" "mail3.example.org!u4" "rjs3 lrswipcda"
+S: A01 OK "Mailbox Activated."
+
+4.10.  Command: STARTTLS
+
+   The STARTTLS command requests the commencement of a [TLS]
+   negotiation.  The negotiation begins immediately after the CRLF in
+   the OK response.  After a client issues a STARTTLS command, it MUST
+   NOT issue further commands until a server response is seen and the
+   [TLS] negotiation is complete.
+
+   The STARTTLS command is only valid in non-authenticated state.  The
+   server remains in non-authenticated state, even if client credentials
+   are supplied during the [TLS] negotiation.  The [SASL] EXTERNAL
+   mechanism MAY be used to authenticate once [TLS] client credentials
+   are successfully exchanged.  Note that servers are not required to
+   support the EXTERNAL mechanism.
+
+   After the [TLS] layer is established, the server MUST re-issue the
+   initial response banner (see Section 3.8).  This is necessary to
+   protect against man-in-the-middle attacks which alter the
+   capabilities list prior to STARTTLS, as well as to advertise any new
+   SASL mechanisms (or other capabilities) that may be available under
+   the layer.  The client MUST discard cached capability information and
+   replace it with the new information.
+
+   After the a successful STARTTLS command, the server SHOULD return a
+   NO response to additional STARTTLS commands.
+
+   Servers MAY choose to not implement STARTTLS.  In this case, they
+   MUST NOT advertise STARTTLS in their capabilities banner, and SHOULD
+   return a BAD response to the STARTTLS command, if it is issued.
+
+   Example:
+
+C: S01 STARTTLS
+S: S01 OK "Begin TLS negotiation now"
+<TLS negotiation, further commands are under TLS layer>
+S: * AUTH KERBEROS_V4 GSSAPI PLAIN
+S: * OK MUPDATE "mupdate.example.org" "Cyrus" "v2.1.2" "(master)"
+
+
+
+Siemborski                    Experimental                     [Page 11]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+4.11.  Command: UPDATE
+
+   The UPDATE command is how a slave initializes an update stream from
+   the master (though it is also valid to issue this command to a
+   slave).  In response to the command, the server returns a list of all
+   mailboxes in its database (the same results as a parameterless LIST
+   command) followed by an OK response.  From this point forward,
+   whenever an update occurs to the master database, it MUST stream the
+   update to the slave within 30 seconds.  That is, it will send
+   RESERVE, MAILBOX, or DELETE responses as they are applicable.
+
+   After a client has issued an UPDATE command, it may only issue NOOP
+   and LOGOUT commands for the remainder of the session.
+
+   Example:
+
+C: U01 UPDATE
+S: U01 MAILBOX "user.leg" "mail2.example.org!u1" "leg lrswipcda"
+S: U01 MAILBOX "user.rjs3" "mail3.example.org!u4" "rjs3 lrswipcda"
+S: U01 RESERVE "internet.bugtraq" "mail1.example.org!u5" "anyone lrs"
+S: U01 OK "Streaming Begins"
+<some time goes by, and another client creates a new mailbox>
+S: U01 RESERVE "user.leg.new" "mail2.example.org!u1"
+<some more time passes, and the create succeeds>
+S: U01 MAILBOX "user.leg.new" "mail2.example.org!u1" "leg lrswipcda"
+<much more time passes, and the slave decides to send a NOOP to reset
+its inactivity timer>
+C: N01 NOOP
+S: U01 DELETE "user.leg.new"
+S: N01 OK "NOOP Complete"
+
+5.  MUPDATE Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].  This uses the ABNF core
+   rules as specified in Appendix A of [ABNF].
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper or lower case characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+   Note that this specification also uses some terminals from section 8
+   of [ACAP].
+
+   cmd-activate = "ACTIVATE" SP string SP string SP string
+
+   cmd-authenticate = "AUTHENTICATE" SP sasl-mech [ SP string ]
+
+
+
+Siemborski                    Experimental                     [Page 12]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+   cmd-delete = "DELETE" SP string
+
+   cmd-find = "FIND" SP string
+
+   cmd-list = "LIST" [ SP string ]
+
+   cmd-logout = "LOGOUT"
+
+   cmd-noop = "NOOP"
+
+   cmd-reserve = "RESERVE" SP string SP string
+
+   cmd-starttls = "STARTTLS"
+
+   cmd-update = "UPDATE"
+
+   command = tag SP command-type CRLF
+
+   command-type = cmd-activate / cmd-authenticate / cmd-delete /
+                  cmd-find / cmd-list / cmd-logout / cmd-noop /
+                  cmd-reserve / cmd-starttls / cmd-update
+
+   response = tag SP response-type CRLF
+
+   response-type = rsp-ok / rsp-no / rsp-bad / rsp-bye / rsp-mailbox /
+                   rsp-reserve / rsp-delete
+
+   rsp-bad = "BAD" SP string
+
+   rsp-bye = "BYE" SP string
+
+   rsp-mailbox = "MAILBOX" SP string SP string SP string
+
+   rsp-no = "NO" SP string
+
+   rsp-ok = "OK" SP string
+
+   rsp-reserve = "RESERVE" SP string SP string
+
+   rsp-delete = "DELETE" SP string
+
+   sasl-mech = 1*ATOM-CHAR
+      ; ATOM-CHAR is defined in [ACAP]
+
+   string = quoted / literal
+      ; quoted and literal are defined in [ACAP]
+
+
+
+
+
+Siemborski                    Experimental                     [Page 13]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+   tag = 1*ATOM-CHAR
+      ; ATOM-CHAR is defined in [ACAP]
+
+6.  MUPDATE URL Scheme
+
+   This document defines the a URL scheme for the purposes of
+   referencing MUPDATE resources, according to the requirements in
+   [RFC2717].  This includes both MUPDATE servers as a whole, along with
+   individual mailbox entries on a given MUPDATE server.
+
+   There is no MIME type associated with these resources.  It is
+   intended that a URL consumer would either retrieve the MUPDATE record
+   in question, or simply connect to the MUPDATE server running on the
+   specified host.  Note that the consumer will need to have
+   authentication credentials for the specified host.
+
+   The MUPDATE URL scheme is similar to the IMAP URL scheme [IMAP-URL].
+   However, it only takes one of two possible forms:
+
+      mupdate://<iserver>/
+      mupdate://<iserver>/<mailbox>
+
+   The first form refers to a MUPDATE server as a whole, the second form
+   indicates both the server and a mailbox to run a FIND against once
+   authenticated to the server.  Note that part of <iserver> may include
+   username and authentication information along with a hostname and
+   port.
+
+6.1.  MUPDATE URL Scheme Registration Form
+
+   URL scheme name: "mupdate"
+
+   URL scheme syntax:
+
+      This defines the MUPDATE URL Scheme in [ABNF].  Terminals from the
+      BNF of IMAP URLs [IMAP-URL] are also used.
+
+         mupdateurl = "mupdate://" iserver "/" [ enc_mailbox ]
+            ; iserver and enc_mailbox are as defined in [IMAP-URL]
+
+   Character encoding considerations:
+
+      Identical to those described in [IMAP-URL] for the appropriate
+      terminals.
+
+
+
+
+
+
+
+Siemborski                    Experimental                     [Page 14]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+   Intended Usage:
+
+      The form of the URL without an associated mailbox is intended to
+      designate a MUPDATE server only.  If a mailbox name is included in
+      the URL, then the consumer is expected to execute a FIND command
+      for that mailbox on the specified server.
+
+   Applications and/or protocols which use this URL scheme name:
+
+      The protocol described in this document.
+
+   Interoperability Considerations:
+
+      None.
+
+   Security Considerations:
+
+      Users of the MUPDATE URL Scheme should review the security
+      considerations that are discussed in [IMAP-URL].  In particular,
+      the consequences of including authentication mechanism information
+      in a URL should be reviewed.
+
+   Relevant Publications:
+
+      This document and [IMAP-URL].
+
+   Author, Change Controller, and Contact for Further Information:
+
+      Author of this document.
+
+7.  Security Considerations
+
+   While no unauthenticated users may make modifications or even perform
+   searches on the database, it is important to note that this
+   specification assumes no protections of any type for authenticated
+   users.
+
+   All authenticated users have complete access to the database.  For
+   this reason it is important to ensure that accounts that are making
+   use of the database are well secured.
+
+   A more secure deployment might have all read only access go through a
+   slave, and only have accounts which need write access use the master.
+   This has the disadvantage of a marginally longer time for updates to
+   reach the clients.
+
+
+
+
+
+
+Siemborski                    Experimental                     [Page 15]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+   The protocol assumes that all authenticated users are cooperating to
+   maintain atomic operations.  Therefore, all new mailboxes SHOULD be
+   RESERVEd before they are ACTIVATEd, despite the fact that the
+   protocol does not require this, and it is therefore possible for a
+   set of participants which do not obey the provided locking to create
+   an inconsistent database.  RESERVEing the mailbox first is not
+   required to perform an activate because this behavior simplifies
+   synchronization with the actual location of the mailboxes.
+
+8.  IANA Considerations
+
+   The IANA has assigned TCP port number 3905 to "mupdate".
+
+   The IANA has registered a URL scheme for the MUPDATE protocol, as
+   defined in section 6.1 of this document.
+
+   IANA has registered a GSSAPI service name of "mupdate" for the
+   MUPDATE protocol in the registry maintained at:
+
+   http://www.iana.org/assignments/gssapi-service-names
+
+9.  Intellectual Property Rights
+
+   The IETF takes no position regarding the validity or scope of any
+   intellectual property or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; neither does it represent that it
+   has made any effort to identify any such rights.  Information on the
+   IETF's procedures with respect to rights in standards-track and
+   standards-related documentation can be found in BCP-11.  Copies of
+   claims of rights made available for publication and any assurances of
+   licenses to be made available, or the result of an attempt made to
+   obtain a general license or permission for the use of such
+   proprietary rights by implementors or users of this specification can
+   be obtained from the IETF Secretariat.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights which may cover technology that may be required to practice
+   this standard.  Please address the information to the IETF Executive
+   Director.
+
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                     [Page 16]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+10.  References
+
+10.1.  Normative References
+
+   [KEYWORDS]  Bradner, S., "Key words for use in RFCs to Indicate
+               Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [IMAP]      Crispin, M., "Internet Message Access Protocol - Version
+               4", RFC 3501, March 2003.
+
+   [ABNF]      Crocker, D., Ed. and P. Overell, "Augmented BNF for
+               Syntax Specifications: ABNF", RFC 2234, November 1997.
+
+   [MIME]      Freed, N. and N. Bornstein, "Multipurpose Internet Mail
+               Extensions (MIME) Part One: Format of Internet Message
+               Bodies", RFC 2045, November 1996.
+
+   [IMAP-ACL]  Myers, J., "IMAP4 ACL extension", RFC 2086, January 1997.
+
+   [SASL]      Myers, J., "Simple Authentication and Security Layer
+               (SASL)", RFC 2222, October 1997.
+
+   [IMAP-URL]  Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+   [ACAP]      Newman, C. and J. Myers, "ACAP -- Application
+               Configuration Access Protocol", RFC 2244, November 1997.
+
+   [TLS]       Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
+               RFC 2246, January 1999.
+
+10.2.  Informative References
+
+   [POP3]      Myers, J. and M. Rose, "Post Office Protocol - Version
+               3", STD 53, RFC 1939, May 1996.
+
+   [RFC2717]   Petke, R. and I. King, "Registration Procedures for URL
+               Scheme Names", BCP 35, RFC 2717, November 1999.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                     [Page 17]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+11.  Acknowledgments
+
+   Lawrence Greenfield and Ken Murchison, for a great deal of input on
+   both the protocol and the text of the documents.
+
+12.  Author's  Address
+
+   Robert Siemborski
+   Carnegie Mellon, Andrew Systems Group
+   Cyert Hall 207
+   5000 Forbes Avenue
+   Pittsburgh, PA  15213
+
+   Phone: (412) 268-7456
+   EMail: rjs3+@andrew.cmu.edu
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                     [Page 18]
+
+RFC 3656     MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+13.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (2003).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assignees.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski                    Experimental                     [Page 19]
+
diff --git a/imap/docs/rfc/rfc3691.txt b/imap/docs/rfc/rfc3691.txt
new file mode 100644
index 00000000..2f4e9b44
--- /dev/null
+++ b/imap/docs/rfc/rfc3691.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group                                        A. Melnikov
+Request for Comments: 3691                                    Isode Ltd.
+Category: Standards Track                                  February 2004
+
+
+        Internet Message Access Protocol (IMAP) UNSELECT command
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2004).  All Rights Reserved.
+
+Abstract
+
+   This document defines an UNSELECT command that can be used to close
+   the current mailbox in an Internet Message Access Protocol - version
+   4 (IMAP4) session without expunging it.  Certain types of IMAP
+   clients need to release resources associated with the selected
+   mailbox without selecting a different mailbox.  While IMAP4 provides
+   this functionality (via a SELECT command with a nonexistent mailbox
+   name or reselecting the same mailbox with EXAMINE command), a more
+   clean solution is desirable.
+
+Table of Contents
+
+   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
+   2.  UNSELECT command . . . . . . . . . . . . . . . . . . . . . . .  2
+   3.  Security Considerations. . . . . . . . . . . . . . . . . . . .  3
+   4.  Formal Syntax. . . . . . . . . . . . . . . . . . . . . . . . .  3
+   5.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . .  3
+   6.  Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . .  3
+   7.  Normative References . . . . . . . . . . . . . . . . . . . . .  4
+   8.  Author's Address . . . . . . . . . . . . . . . . . . . . . . .  4
+   9.  Full Copyright Statement . . . . . . . . . . . . . . . . . . .  5
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 1]
+
+RFC 3691                 IMAP UNSELECT command             February 2004
+
+
+1.  Introduction
+
+   Certain types of IMAP clients need to release resources associated
+   with the selected mailbox without selecting a different mailbox.
+   While [IMAP4] provides this functionality (via a SELECT command with
+   a nonexistent mailbox name or reselecting the same mailbox with
+   EXAMINE command), a more clean solution is desirable.
+
+   [IMAP4] defines the CLOSE command that closes the selected mailbox as
+   well as permanently removes all messages with the \Deleted flag set.
+
+   However [IMAP4] lacks a command that simply closes the mailbox
+   without expunging it.  This document defines the UNSELECT command for
+   this purpose.
+
+   A server which supports this extension indicates this with a
+   capability name of "UNSELECT".
+
+   "C:" and "S:" in examples show lines sent by the client and server
+   respectively.
+
+   The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in
+   this document when typed in uppercase are to be interpreted as
+   defined in "Key words for use in RFCs to Indicate Requirement Levels"
+   [KEYWORDS].
+
+2.  UNSELECT Command
+
+   Arguments:  none
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - unselect completed, now in authenticated state
+               BAD - no mailbox selected, or argument supplied but
+                     none permitted
+
+      The UNSELECT command frees server's resources associated with the
+      selected mailbox and returns the server to the authenticated
+      state.  This command performs the same actions as CLOSE, except
+      that no messages are permanently removed from the currently
+      selected mailbox.
+
+   Example:    C: A341 UNSELECT
+               S: A341 OK Unselect completed
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 2]
+
+RFC 3691                 IMAP UNSELECT command             February 2004
+
+
+3.  Security Considerations
+
+   It is believed that this extension doesn't raise any additional
+   security concerns not already discussed in [IMAP4].
+
+4.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].  Non-terminals
+   referenced but not defined below are as defined by [IMAP4].
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper or lower case characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+   command-select  /= "UNSELECT"
+
+5.  IANA Considerations
+
+   IMAP4 capabilities are registered by publishing a standards track or
+   IESG approved experimental RFC.  The registry is currently located
+   at:
+
+      http://www.iana.org/assignments/imap4-capabilities
+
+   This document defines the UNSELECT IMAP capabilities.  IANA has added
+   this capability to the registry.
+
+6.  Acknowledgments
+
+   UNSELECT command was originally implemented by Tim Showalter in Cyrus
+   IMAP server.
+
+   Also, the author of the document would like to thank Vladimir Butenko
+   and Mark Crispin for reminding that UNSELECT has to be documented.
+   Also thanks to Simon Josefsson for pointing out that there are
+   multiple ways to implement UNSELECT.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 3]
+
+RFC 3691                 IMAP UNSELECT command             February 2004
+
+
+7.  Normative References
+
+   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [IMAP4]    Crispin, M., "Internet Message Access Protocol - Version
+              4rev1", RFC 3501, March 2003.
+
+   [ABNF]     Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
+              Specifications: ABNF", RFC 2234, November 1997.
+
+8.  Author's Address
+
+   Alexey Melnikov
+   Isode Limited
+   5 Castle Business Village
+   Hampton, Middlesex TW12 2BX
+
+   EMail: Alexey.Melnikov@isode.com
+   URI: http://www.melnikov.ca/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 4]
+
+RFC 3691                 IMAP UNSELECT command             February 2004
+
+
+9.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (2004).  This document is subject
+   to the rights, licenses and restrictions contained in BCP 78 and
+   except as set forth therein, the authors retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
+   REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
+   INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed
+   to pertain to the implementation or use of the technology
+   described in this document or the extent to which any license
+   under such rights might or might not be available; nor does it
+   represent that it has made any independent effort to identify any
+   such rights.  Information on the procedures with respect to
+   rights in RFC documents can be found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use
+   of such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository
+   at http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention
+   any copyrights, patents or patent applications, or other
+   proprietary rights that may cover technology that may be required
+   to implement this standard.  Please address the information to the
+   IETF at ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 5]
+
diff --git a/imap/docs/rfc/rfc4314.txt b/imap/docs/rfc/rfc4314.txt
new file mode 100644
index 00000000..e73a56f2
--- /dev/null
+++ b/imap/docs/rfc/rfc4314.txt
@@ -0,0 +1,1515 @@
+
+
+
+
+
+
+Network Working Group                                        A. Melnikov
+Request for Comments: 4314                                    Isode Ltd.
+Obsoletes: 2086                                            December 2005
+Category: Standards Track
+
+
+               IMAP4 Access Control List (ACL) Extension
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2005).
+
+Abstract
+
+   The Access Control List (ACL) extension (RFC 2086) of the Internet
+   Message Access Protocol (IMAP) permits mailbox access control lists
+   to be retrieved and manipulated through the IMAP protocol.
+
+   This document is a revision of RFC 2086.  It defines several new
+   access control rights and clarifies which rights are required for
+   different IMAP commands.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 1]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+Table of Contents
+
+   1. Introduction and Overview .......................................3
+      1.1. Conventions Used in This Document ..........................3
+   2. Access Control ..................................................3
+      2.1. Standard Rights ............................................5
+           2.1.1. Obsolete Rights .....................................5
+      2.2. Rights Defined in RFC 2086 .................................8
+   3. Access control management commands and responses ................8
+      3.1. SETACL Command .............................................8
+      3.2. DELETEACL Command ..........................................9
+      3.3. GETACL Command ............................................10
+      3.4. LISTRIGHTS Command ........................................10
+      3.5. MYRIGHTS Command ..........................................11
+      3.6. ACL Response ..............................................11
+      3.7. LISTRIGHTS Response .......................................12
+      3.8. MYRIGHTS Response .........................................12
+   4. Rights Required to Perform Different IMAP4rev1 Commands ........12
+   5. Other Considerations ...........................................17
+      5.1. Additional Requirements and Implementation Notes ..........17
+           5.1.1. Servers ............................................17
+           5.1.2. Clients ............................................18
+      5.2. Mapping of ACL Rights to READ-WRITE and READ-ONLY
+           Response Codes ............................................19
+   6. Security Considerations ........................................20
+   7. Formal Syntax ..................................................21
+   8. IANA Considerations ............................................22
+   9. Internationalization Considerations ............................22
+   Appendix A. Changes since RFC 2086 ................................23
+   Appendix B. Compatibility with RFC 2086 ...........................24
+   Appendix C. Known Deficiencies ....................................24
+   Appendix D. Acknowledgements ......................................25
+   Normative References ..............................................25
+   Informative References ............................................25
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 2]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+1.  Introduction and Overview
+
+   The ACL (Access Control List) extension of the Internet Message
+   Access Protocol [IMAP4] permits mailbox access control lists to be
+   retrieved and manipulated through the IMAP protocol.
+
+   This document is a revision of RFC 2086 [RFC2086].  It tries to
+   clarify different ambiguities in RFC 2086, in particular, the use of
+   UTF-8 [UTF-8] in access identifiers, which rights are required for
+   different IMAP4 commands, and how READ-WRITE/READ-ONLY response codes
+   are related to ACL.
+
+1.1.  Conventions Used in This Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.
+
+   In all examples "/" character is used as hierarchy separator.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+   The phrase "ACL server" is just a shortcut for saying "IMAP server
+   that supports ACL extension as defined in this document".
+
+2.  Access Control
+
+   The ACL extension is present in any IMAP4 implementation that returns
+   "ACL" as one of the supported capabilities to the CAPABILITY command.
+
+   A server implementation conformant to this document MUST also return
+   rights (see below) not defined in Section 2.2 in the "RIGHTS="
+   capability.
+
+   An access control list is a set of <access identifier,rights> pairs.
+   An ACL applies to a mailbox name.
+
+   Access identifier (or just "identifier") is a UTF-8 [UTF-8] string.
+   The identifier "anyone" is reserved to refer to the universal
+   identity (all authentications, including anonymous).  All user name
+   strings accepted by the LOGIN or AUTHENTICATE commands to
+   authenticate to the IMAP server are reserved as identifiers for the
+   corresponding users.  Identifiers starting with a dash ("-") are
+   reserved for "negative rights", described below.  All other
+   identifier strings are interpreted in an implementation-defined
+   manner.
+
+
+
+
+Melnikov                    Standards Track                     [Page 3]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   Rights is a string listing a (possibly empty) set of alphanumeric
+   characters, each character listing a set of operations that is being
+   controlled.  Lowercase letters are reserved for "standard" rights,
+   listed in Section 2.1.  (Note that for compatibility with deployed
+   clients and servers uppercase rights are not allowed.)  The set of
+   standard rights can only be extended by a standards-track document.
+   Digits are reserved for implementation- or site-defined rights.
+
+   An implementation MAY tie rights together or MAY force rights to
+   always or never be granted to particular identifiers.  For example,
+   in an implementation that uses UNIX mode bits, the rights "swite" are
+   tied, the "a" right is always granted to the owner of a mailbox and
+   is never granted to another user.  If rights are tied in an
+   implementation, the implementation must be conservative in granting
+   rights in response to SETACL commands--unless all rights in a tied
+   set are specified, none of that set should be included in the ACL
+   entry for that identifier.  A client can discover the set of rights
+   that may be granted to a given identifier in the ACL for a given
+   mailbox name by using the LISTRIGHTS command.
+
+   It is possible for multiple identifiers in an access control list to
+   apply to a given user.  For example, an ACL may include rights to be
+   granted to the identifier matching the user, one or more
+   implementation-defined identifiers matching groups that include the
+   user, and/or the identifier "anyone".  How these rights are combined
+   to determine the user's access is implementation defined.  An
+   implementation may choose, for example, to use the union of the
+   rights granted to the applicable identifiers.  An implementation may
+   instead choose, for example, to use only those rights granted to the
+   most specific identifier present in the ACL.  A client can determine
+   the set of rights granted to the logged-in user for a given mailbox
+   name by using the MYRIGHTS command.
+
+   When an identifier in an ACL starts with a dash ("-"), that indicates
+   that associated rights are to be removed from the identifier prefixed
+   by the dash.  This is referred to as a "negative right".  This
+   differs from DELETEACL in that a negative right is added to the ACL
+   and is a part of the calculation of the rights.
+
+   Let's assume that an identifier "fred" refers to a user with login
+   "fred".  If the identifier "-fred" is granted the "w" right, that
+   indicates that the "w" right is to be removed from users matching the
+   identifier "fred", even though the user "fred" might have the "w"
+   right as a consequence of some other identifier in the ACL.  A
+   DELETEACL of "fred" simply deletes the identifier "fred" from the
+   ACL; it does not affect any rights that the user "fred" may get from
+   another entry in the ACL, in particular it doesn't affect rights
+   granted to the identifier "-fred".
+
+
+
+Melnikov                    Standards Track                     [Page 4]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   Server implementations are not required to support "negative right"
+   identifiers.
+
+2.1.  Standard Rights
+
+   The currently defined standard rights are (note that the list below
+   doesn't list all commands that use a particular right):
+
+   l - lookup (mailbox is visible to LIST/LSUB commands, SUBSCRIBE
+       mailbox)
+   r - read (SELECT the mailbox, perform STATUS)
+   s - keep seen/unseen information across sessions (set or clear
+       \SEEN flag via STORE, also set \SEEN during APPEND/COPY/
+       FETCH BODY[...])
+   w - write (set or clear flags other than \SEEN and \DELETED via
+       STORE, also set them during APPEND/COPY)
+   i - insert (perform APPEND, COPY into mailbox)
+   p - post (send mail to submission address for mailbox,
+       not enforced by IMAP4 itself)
+   k - create mailboxes (CREATE new sub-mailboxes in any
+       implementation-defined hierarchy, parent mailbox for the new
+       mailbox name in RENAME)
+   x - delete mailbox (DELETE mailbox, old mailbox name in RENAME)
+   t - delete messages (set or clear \DELETED flag via STORE, set
+       \DELETED flag during APPEND/COPY)
+   e - perform EXPUNGE and expunge as a part of CLOSE
+   a - administer (perform SETACL/DELETEACL/GETACL/LISTRIGHTS)
+
+2.1.1.  Obsolete Rights
+
+   Due to ambiguity in RFC 2086, some existing RFC 2086 server
+   implementations use the "c" right to control the DELETE command.
+   Others chose to use the "d" right to control the DELETE command.  For
+   the former group, let's define the "create" right as union of the "k"
+   and "x" rights, and the "delete" right as union of the "e" and "t"
+   rights.  For the latter group, let's define the "create" rights as a
+   synonym to the "k" right, and the "delete" right as union of the "e",
+   "t", and "x" rights.
+
+   For compatibility with RFC 2086, this section defines two virtual
+   rights "d" and "c".
+
+   If a client includes the "d" right in a rights list, then it MUST be
+   treated as if the client had included every member of the "delete"
+   right.  (It is not an error for a client to specify both the "d"
+   right and one or more members of the "delete" right, but the effect
+   is no different than if just the "d" right or all members of the
+   "delete" right had been specified.)
+
+
+
+Melnikov                    Standards Track                     [Page 5]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   When any of the "delete" member rights is set in a list of rights,
+   the server MUST also include the "d" right when returning the list in
+   a MYRIGHTS or ACL response.  This is to enable older clients
+   conforming to RFC 2086 to work with newer servers. (*)
+
+   Example:    C: A001 SeTacl INBOX/Drafts David lrswida
+               S: A001 OK Setacl complete
+
+   The client has specified the "d" right in the SETACL command above
+   and it expands to "et" on the server:
+
+               C: A002 getacl INBOX/Drafts
+               S: * ACL INBOX Fred rwipslxcetda David lrswideta
+               S: A002 OK Getacl complete
+
+   If the identifier specified in the LISTRIGHTS command can be granted
+   any of the "delete" member rights on a mailbox, then the server MUST
+   include the "d" right in the corresponding LISTRIGHTS response. (*)
+   If the member rights aren't tied to non-member rights, then the "d"
+   right is returned by itself in the LISTRIGHTS response.  If any of
+   the member rights needs to be tied to one (or more) non-member right,
+   then the "d" right and all of the member rights need to be tied to
+   the same non-member right(s) (**).
+
+   If a client includes the "c" right in a rights list, then it MUST be
+   treated as if the client had included every member of the "create"
+   right.  (It is not an error for a client to specify both the "c"
+   right and one or more members of the "create" right, but the effect
+   is no different than if just the "c" right or all members of the
+   "create" right had been specified.)
+
+   When any of the "create" member rights is set in a list of rights,
+   the server MUST also include the "c" right when returning the list in
+   a MYRIGHTS or ACL response.  This is to enable older clients
+   conforming to RFC 2086 to work with newer servers. (*)
+
+   Example:    C: A003 Setacl INBOX/Drafts Byron lrswikda
+               S: A001 OK Setacl complete
+               C: A002 getAcl INBOX/Drafts
+               S: * ACL INBOX Fred rwipslxcetda Byron lrswikcdeta
+               S: A002 OK Getacl complete
+
+   The client has specified the "d" right in the SETACL command above
+   and it expands to "et" on the server: As the client has specified the
+   "k" right (which is a member of the "c" right), the server also
+   returns the "c" right.
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 6]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   If the identifier specified in the LISTRIGHTS command can be granted
+   any of the "create" member rights on a mailbox, then the server MUST
+   include the "c" right in the corresponding LISTRIGHTS response. (*)
+   If the member rights aren't tied to non-member rights, then the "c"
+   right is returned by itself in the LISTRIGHTS response.  If any of
+   the member rights needs to be tied to one (or more) non-member right,
+   then the "c" right and all of the member rights need to be tied to
+   the same non-member right(s) (**).
+
+   Example: The server that ties the rights as follows:
+
+               lr s w i p k x t
+
+            and c=k
+
+            will return:
+
+               S: * LISTRIGHTS archive/imap anyone ""
+                  lr s w i p k x t c d
+
+   Example: The server that ties the rights as follows:
+
+               lr s w i p k xte
+
+            and c=k
+
+            will return:
+
+               S: * LISTRIGHTS archive/imap anyone ""
+                  lr s w i p k xte c d
+
+   Example: The server that ties the rights as follows:
+
+               lr s w i p k x te
+
+            and c=k
+
+            will return:
+
+               S: * LISTRIGHTS archive/imap anyone ""
+                  lr s w i p k c x te d
+
+   Example: The server that ties the rights as follows:
+
+               lr swte i p k x
+
+            and c=kx
+
+
+
+
+Melnikov                    Standards Track                     [Page 7]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+            will return:
+
+               S: * LISTRIGHTS archive/imap anyone ""
+                  lr swted i p k x c
+
+   (*)  Clients conforming to this document MUST ignore the virtual "d"
+        and "c" rights in MYRIGHTS, ACL, and LISTRIGHTS responses.
+
+   (**) The IMAPEXT Working Group has debated this issue in great length
+        and after reviewing existing ACL implementations concluded that
+        this is a reasonable restriction.
+
+2.2.  Rights Defined in RFC 2086
+
+   The "RIGHTS=" capability MUST NOT include any of the rights defined
+   in RFC 2086: "l", "r", "s", "w", "i", "p", "a", "c", "d", and the
+   digits ("0" .. "9").
+
+3.  Access control management commands and responses
+
+   Servers, when processing a command that has an identifier as a
+   parameter (i.e., any of SETACL, DELETEACL, and LISTRIGHTS commands),
+   SHOULD first prepare the received identifier using "SASLprep" profile
+   [SASLprep] of the "stringprep" algorithm [Stringprep].  If the
+   preparation of the identifier fails or results in an empty string,
+   the server MUST refuse to perform the command with a BAD response.
+   Note that Section 6 recommends additional identifier's verification
+   steps.
+
+3.1.  SETACL Command
+
+   Arguments:  mailbox name
+               identifier
+               access right modification
+
+   Data:       no specific data for this command
+
+   Result:     OK - setacl completed
+               NO - setacl failure: can't set acl
+               BAD - arguments invalid
+
+   The SETACL command changes the access control list on the specified
+   mailbox so that the specified identifier is granted permissions as
+   specified in the third argument.
+
+   The third argument is a string containing an optional plus ("+") or
+   minus ("-") prefix, followed by zero or more rights characters.  If
+   the string starts with a plus, the following rights are added to any
+
+
+
+Melnikov                    Standards Track                     [Page 8]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   existing rights for the identifier.  If the string starts with a
+   minus, the following rights are removed from any existing rights for
+   the identifier.  If the string does not start with a plus or minus,
+   the rights replace any existing rights for the identifier.
+
+   Note that an unrecognized right MUST cause the command to return the
+   BAD response.  In particular, the server MUST NOT silently ignore
+   unrecognized rights.
+
+   Example:    C: A001 GETACL INBOX/Drafts
+               S: * ACL INBOX/Drafts Fred rwipslxetad Chris lrswi
+               S: A001 OK Getacl complete
+               C: A002 SETACL INBOX/Drafts Chris +cda
+               S: A002 OK Setacl complete
+               C: A003 GETACL INBOX/Drafts
+               S: * ACL INBOX/Drafts Fred rwipslxetad Chris lrswicdakxet
+               S: A003 OK Getacl complete
+
+
+               C: A035 SETACL INBOX/Drafts John lrQswicda
+               S: A035 BAD Uppercase rights are not allowed
+
+
+               C: A036 SETACL INBOX/Drafts John lrqswicda
+               S: A036 BAD The q right is not supported
+
+3.2.  DELETEACL Command
+
+   Arguments:  mailbox name
+               identifier
+
+   Data:       no specific data for this command
+
+   Result:     OK - deleteacl completed
+               NO - deleteacl failure: can't delete acl
+              BAD - arguments invalid
+
+   The DELETEACL command removes any <identifier,rights> pair for the
+   specified identifier from the access control list for the specified
+   mailbox.
+
+   Example:    C: B001 getacl INBOX
+               S: * ACL INBOX Fred rwipslxetad -Fred wetd $team w
+               S: B001 OK Getacl complete
+               C: B002 DeleteAcl INBOX Fred
+               S: B002 OK Deleteacl complete
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 9]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+               C: B003 GETACL INBOX
+               S: * ACL INBOX -Fred wetd $team w
+               S: B003 OK Getacl complete
+
+3.3.  GETACL Command
+
+   Arguments:  mailbox name
+
+   Data:       untagged responses: ACL
+
+   Result:     OK - getacl completed
+               NO - getacl failure: can't get acl
+              BAD - arguments invalid
+
+   The GETACL command returns the access control list for mailbox in an
+   untagged ACL response.
+
+   Some implementations MAY permit multiple forms of an identifier to
+   reference the same IMAP account.  Usually, such implementations will
+   have a canonical form that is stored internally.  An ACL response
+   caused by a GETACL command MAY include a canonicalized form of the
+   identifier that might be different from the one used in the
+   corresponding SETACL command.
+
+   Example:    C: A002 GETACL INBOX
+               S: * ACL INBOX Fred rwipsldexta
+               S: A002 OK Getacl complete
+
+3.4.  LISTRIGHTS Command
+
+   Arguments:  mailbox name
+               identifier
+
+   Data:       untagged responses: LISTRIGHTS
+
+   Result:     OK - listrights completed
+               NO - listrights failure: can't get rights list
+               BAD - arguments invalid
+
+   The LISTRIGHTS command takes a mailbox name and an identifier and
+   returns information about what rights can be granted to the
+   identifier in the ACL for the mailbox.
+
+   Some implementations MAY permit multiple forms of an identifier to
+   reference the same IMAP account.  Usually, such implementations will
+   have a canonical form that is stored internally.  A LISTRIGHTS
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 10]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   response caused by a LISTRIGHTS command MUST always return the same
+   form of an identifier as specified by the client.  This is to allow
+   the client to correlate the response with the command.
+
+   Example:    C: a001 LISTRIGHTS ~/Mail/saved smith
+               S: * LISTRIGHTS ~/Mail/saved smith la r swicdkxte
+               S: a001 OK Listrights completed
+
+   Example:    C: a005 listrights archive/imap anyone
+               S: * LISTRIGHTS archive.imap anyone ""
+                  l r s w i p k x t e c d a 0 1 2 3 4 5 6 7 8 9
+               S: a005 Listrights successful
+
+3.5.  MYRIGHTS Command
+
+   Arguments:  mailbox name
+
+   Data:       untagged responses: MYRIGHTS
+
+   Result:     OK - myrights completed
+               NO - myrights failure: can't get rights
+               BAD - arguments invalid
+
+   The MYRIGHTS command returns the set of rights that the user has to
+   mailbox in an untagged MYRIGHTS reply.
+
+   Example:    C: A003 MYRIGHTS INBOX
+               S: * MYRIGHTS INBOX rwiptsldaex
+               S: A003 OK Myrights complete
+
+3.6.  ACL Response
+
+   Data:       mailbox name
+               zero or more identifier rights pairs
+
+   The ACL response occurs as a result of a GETACL command.  The first
+   string is the mailbox name for which this ACL applies.  This is
+   followed by zero or more pairs of strings; each pair contains the
+   identifier for which the entry applies followed by the set of rights
+   that the identifier has.
+
+   Section 2.1.1 details additional server requirements related to
+   handling of the virtual "d" and "c" rights.
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 11]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+3.7.  LISTRIGHTS Response
+
+   Data:       mailbox name
+               identifier
+               required rights
+               list of optional rights
+
+   The LISTRIGHTS response occurs as a result of a LISTRIGHTS command.
+   The first two strings are the mailbox name and identifier for which
+   this rights list applies.  Following the identifier is a string
+   containing the (possibly empty) set of rights the identifier will
+   always be granted in the mailbox.
+
+   Following this are zero or more strings each containing a set of
+   rights the identifier can be granted in the mailbox.  Rights
+   mentioned in the same string are tied together.  The server MUST
+   either grant all tied rights to the identifier in the mailbox or
+   grant none.  Section 2.1.1 details additional server requirements
+   related to handling of the virtual "d" and "c" rights.
+
+   The same right MUST NOT be listed more than once in the LISTRIGHTS
+   command.
+
+3.8.  MYRIGHTS Response
+
+   Data:       mailbox name
+               rights
+
+   The MYRIGHTS response occurs as a result of a MYRIGHTS command.  The
+   first string is the mailbox name for which these rights apply.  The
+   second string is the set of rights that the client has.
+
+   Section 2.1.1 details additional server requirements related to
+   handling of the virtual "d" and "c" rights.
+
+4.  Rights Required to Perform Different IMAP4rev1 Commands
+
+   Before executing a command, an ACL-compliant server MUST check which
+   rights are required to perform it.  This section groups command by
+   functions they perform and list the rights required.  It also gives
+   the detailed description of any special processing required.
+
+   For the purpose of this section the UID counterpart of a command is
+   considered to be the same command, e.g., both UID COPY and COPY
+   commands require the same set of rights.
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 12]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   The table below summarizes different rights or their combinations
+   that are required in order to perform different IMAP operations.  As
+   it is not always possible to express complex right checking and
+   interactions, the description after the table should be used as the
+   primary reference.
+
+   +-------------------+---+---+---+---+---+---+---+---+---+---+---+---+
+   |Operations\Rights  | l | r | s | w | i | k | x | t | e | a |Any|Non|
+   +-------------------+---+---+---+---+---+---+---+---+---+---+---+---+
+   |                  commands in authenticated state                  |
+   +-------------------------------------------------------------------+
+   |      LIST         | + |   |   |   |   |   |   |   |   |   |   |   |
+   |   SUBSCRIBE       | * |   |   |   |   |   |   |   |   |   |   | * |
+   |  UNSUBSCRIBE      |   |   |   |   |   |   |   |   |   |   |   | + |
+   |      LSUB         | * |   |   |   |   |   |   |   |   |   |   | * |
+   |CREATE (for parent)|   |   |   |   |   | + |   |   |   |   |   |   |
+   |     DELETE        |   | ? |   |   |   |   | + | ? | ? |   |   |   |
+   |     RENAME        |   |   |   |   |   | + | + |   |   |   |   |   |
+   |  SELECT/EXAMINE   |   | + |   |   |   |   |   |   |   |   |   |   |
+   |      STATUS       |   | + |   |   |   |   |   |   |   |   |   |   |
+   |  SETACL/DELETEACL |   |   |   |   |   |   |   |   |   | + |   |   |
+   | GETACL/LISTRIGHTS |   |   |   |   |   |   |   |   |   | + |   |   |
+   |     MYRIGHTS      |   |   |   |   |   |   |   |   |   |   | + |   |
+   |      APPEND       |   |   | ? | ? | + |   |   | ? |   |   |   |   |
+   +-------------------------------------------------------------------+
+   |                     commands in selected state                    |
+   +-------------------------------------------------------------------+
+   |       COPY        |   |   | ? | ? | + |   |   | ? |   |   |   |   |
+   |     EXPUNGE       |   |   |   |   |   |   |   |   | + |   |   |   |
+   |      CLOSE        |   |   |   |   |   |   |   |   | ? |   |   |   |
+   |      FETCH        |   |   | ? |   |   |   |   |   |   |   |   |   |
+   |   STORE flags     |   |   | ? | ? |   |   |   | ? |   |   |   |   |
+   +-------------------+---+---+---+---+---+---+---+---+---+---+---+---+
+
+   Note: for all commands in the selected state, the "r" is implied,
+   because it is required to SELECT/EXAMINE a mailbox.  Servers are not
+   required to check presence of the "r" right once a mailbox is
+   successfully selected.
+
+   Legend:
+    +     - The right is required
+    *     - Only one of the rights marked with * is required
+            (see description below)
+    ?     - The right is OPTIONAL (see description below)
+    "Any" - at least one of the "l", "r", "i", "k", "x", "a" rights is
+            required
+    "Non" - No rights required to perform the command
+
+
+
+
+Melnikov                    Standards Track                    [Page 13]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   Listing and subscribing/unsubscribing mailboxes:
+      LIST - "l" right is required.  However, unlike other commands
+      (e.g., SELECT) the server MUST NOT return a NO response if it
+      can't list a mailbox.
+      Note that if the user has "l" right to a mailbox "A/B", but not to
+      its parent mailbox "A", the LIST command should behave as if the
+      mailbox "A" doesn't exist, for example:
+
+               C: A777 LIST "" *
+               S: * LIST (\NoInferiors) "/" "A/B"
+               S: * LIST () "/" "C"
+               S: * LIST (\NoInferiors) "/" "C/D"
+               S: A777 OK LIST completed
+
+
+      SUBSCRIBE - "l" right is required only if the server checks for
+      mailbox existence when performing SUBSCRIBE.
+
+      UNSUBSCRIBE - no rights required to perform this operation.
+
+      LSUB - "l" right is required only if the server checks for mailbox
+      existence when performing SUBSCRIBE.  However, unlike other
+      commands (e.g., SELECT) the server MUST NOT return a NO response
+      if it can't list a subscribed mailbox.
+
+   Mailbox management:
+      CREATE - "k" right on a nearest existing parent mailbox.  When a
+      new mailbox is created, it SHOULD inherit the ACL from the parent
+      mailbox (if one exists) in the defined hierarchy.
+
+      DELETE - "x" right on the mailbox.  Note that some servers don't
+      allow to delete a non-empty mailbox.  If this is the case, the
+      user would also need "r", "e", and "t" rights, in order to open
+      the mailbox and empty it.
+
+      The DELETE command MUST delete the ACL associated with the deleted
+      mailbox.
+
+      RENAME - Moving a mailbox from one parent to another requires the
+      "x" right on the mailbox itself and the "k" right for the new
+      parent.  For example, if the user wants to rename the mailbox
+      named "A/B/C" to "D/E", the user must have the "x" right for the
+      mailbox "A/B/C" and the "k" right for the mailbox "D".
+      The RENAME command SHOULD NOT change the ACLs on the renamed
+      mailbox and submailboxes.
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 14]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   Copying or appending messages:
+      Before performing a COPY/APPEND command, the server MUST check if
+      the user has "i" right for the target mailbox.  If the user
+      doesn't have "i" right, the operation fails.  Otherwise for each
+      copied/appended message the server MUST check if the user has
+         "t" right - when the message has \Deleted flag set
+         "s" right - when the message has \Seen flag set
+         "w" right - for all other message flags.
+      Only when the user has a particular right are the corresponding
+      flags stored for the newly created message.  The server MUST NOT
+      fail a COPY/APPEND if the user has no rights to set a particular
+      flag.
+
+   Example:    C: A003 MYRIGHTS TargetMailbox
+               S: * MYRIGHTS TargetMailbox rwis
+               S: A003 OK Myrights complete
+
+               C: A004 FETCH 1:3 (FLAGS)
+               S: * 1 FETCH (FLAGS (\Draft \Deleted)
+               S: * 2 FETCH (FLAGS (\Answered)
+               S: * 3 FETCH (FLAGS ($Forwarded \Seen)
+               S: A004 OK Fetch Completed
+
+               C: A005 COPY 1:3 TargetMailbox
+               S: A005 OK Copy completed
+
+               C: A006 SELECT TargetMailbox
+                  ...
+               S: A006 Select Completed
+
+      Let's assume that the copied messages received message numbers
+      77:79.
+
+               C: A007 FETCH 77:79 (FLAGS)
+               S: * 77 FETCH (FLAGS (\Draft))
+               S: * 78 FETCH (FLAGS (\Answered))
+               S: * 79 FETCH (FLAGS ($Forwarded \Seen))
+               S: A007 OK Fetch Completed
+
+      \Deleted flag was lost on COPY, as the user has no "t" right in
+      the target mailbox.
+      If the MYRIGHTS command with the tag A003 would have returned:
+
+               S: * MYRIGHTS TargetMailbox rsti
+
+      the response from the FETCH with the tag A007 would have been:
+
+               C: A007 FETCH 77:79 (FLAGS)
+
+
+
+Melnikov                    Standards Track                    [Page 15]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+               S: * 77 FETCH (FLAGS (\Deleted))
+               S: * 78 FETCH (FLAGS ())
+               S: * 79 FETCH (FLAGS (\Seen))
+               S: A007 OK Fetch Completed
+
+      In the latter case, \Answered, $Forwarded, and \Draft flags were
+      lost on COPY, as the user has no "w" right in the target mailbox.
+
+   Expunging the selected mailbox:
+      EXPUNGE - "e" right on the selected mailbox.
+
+      CLOSE - "e" right on the selected mailbox.  If the server is
+      unable to expunge the mailbox because the user doesn't have the
+      "e" right, the server MUST ignore the expunge request, close the
+      mailbox, and return the tagged OK response.
+
+   Fetch information about a mailbox and its messages:
+      SELECT/EXAMINE/STATUS - "r" right on the mailbox.
+
+      FETCH - A FETCH request that implies setting \Seen flag MUST NOT
+      set it, if the current user doesn't have "s" right.
+
+   Changing flags:
+      STORE - the server MUST check if the user has
+         "t" right - when the user modifies \Deleted flag
+         "s" right - when the user modifies \Seen flag
+         "w" right - for all other message flags.
+      STORE operation SHOULD NOT fail if the user has rights to modify
+      at least one flag specified in the STORE, as the tagged NO
+      response to a STORE command is not handled very well by deployed
+      clients.
+
+   Changing ACLs:
+      SETACL/DELETEACL - "a" right on the mailbox.
+
+   Reading ACLs:
+      GETACL - "a" right on the mailbox.
+
+      MYRIGHTS - any of the following rights is required to perform the
+      operation: "l", "r", "i", "k", "x", "a".
+
+      LISTRIGHTS - "a" right on the mailbox.
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 16]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+5.  Other Considerations
+
+5.1.  Additional Requirements and Implementation Notes
+
+5.1.1.  Servers
+
+   This document defines an additional capability that is used to
+   announce the list of extra rights (excluding the ones defined in RFC
+   2086) supported by the server.  The set of rights MUST include "t",
+   "e", "x", and "k".  Note that the extra rights can appear in any
+   order.
+
+   Example:    C: 1 capability
+               S: * CAPABILITY IMAP4REV1 STARTTLS LITERAL+
+                  ACL RIGHTS=texk
+               S: 1 OK completed
+
+   Any server implementing an ACL extension MUST accurately reflect the
+   current user's rights in FLAGS and PERMANENTFLAGS responses.
+
+   Example:    C: A142 SELECT INBOX
+               S: * 172 EXISTS
+               S: * 1 RECENT
+               S: * OK [UNSEEN 12] Message 12 is first unseen
+               S: * OK [UIDVALIDITY 3857529045] UIDs valid
+               S: * OK [UIDNEXT 4392] Predicted next UID
+               S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+               S: * OK [PERMANENTFLAGS (\Seen \Answered \Flagged \*)] L
+               S: A142 OK [READ-WRITE] SELECT completed
+               C: A143 MYRIGHTS INBOX
+               S: * MYRIGHTS INBOX lrwis
+               S: A143 OK completed
+
+   Note that in order to get better performance the client MAY pipeline
+   SELECT and MYRIGHTS commands:
+
+               C: A142 SELECT INBOX
+               C: A143 MYRIGHTS INBOX
+               S: * 172 EXISTS
+               S: * 1 RECENT
+               S: * OK [UNSEEN 12] Message 12 is first unseen
+               S: * OK [UIDVALIDITY 3857529045] UIDs valid
+               S: * OK [UIDNEXT 4392] Predicted next UID
+               S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+               S: * OK [PERMANENTFLAGS (\Seen \Answered \Flagged \*)] L
+               S: A142 OK [READ-WRITE] SELECT completed
+               S: * MYRIGHTS INBOX lrwis
+               S: A143 OK completed
+
+
+
+Melnikov                    Standards Track                    [Page 17]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   Servers MAY cache the rights a user has on a mailbox when the mailbox
+   is selected, so that if a client's rights on a mailbox are changed
+   with SETACL or DELETEACL, commands specific to the selected state
+   (e.g., STORE, EXPUNGE) might not reflect the changed rights until the
+   mailbox is re-selected.  If the server checks the rights on each
+   command, then it SHOULD send FLAGS and PERMANENTFLAGS responses if
+   they have changed.  If such server detects that the user no longer
+   has read access to the mailbox, it MAY send an untagged BYE response
+   and close connection.  It MAY also refuse to execute all commands
+   specific to the selected state until the mailbox is closed; however,
+   server implementors should note that most clients don't handle NO
+   responses very well.
+
+   An ACL server MAY modify one or more ACLs for one or more identifiers
+   as a side effect of modifying the ACL specified in a
+   SETACL/DELETEACL.  If the server does that, it MUST send untagged ACL
+   response(s) to notify the client about the changes made.
+
+   An ACL server implementation MUST treat received ACL modification
+   commands as a possible ambiguity with respect to subsequent commands
+   affected by the ACL, as described in Section 5.5 of [IMAP4].  Hence a
+   pipeline SETACL + MYRIGHTS is an ambiguity with respect to the
+   server, meaning that the server must execute the SETACL command to
+   completion before the MYRIGHTS.  However, clients are permitted to
+   send such a pipeline.
+
+5.1.2.  Clients
+
+   The following requirement is put on clients in order to allow for
+   future extensibility.  A client implementation that allows a user to
+   read and update ACLs MUST preserve unrecognized rights that it
+   doesn't allow the user to change.  That is, if the client
+
+   1) can read ACLs
+    and
+   2) can update ACLs
+    but
+   3) doesn't allow the user to change the rights the client doesn't
+   recognize, then it MUST preserve unrecognized rights.
+
+   Otherwise the client could risk unintentionally removing permissions
+   it doesn't understand.
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 18]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+5.2.  Mapping of ACL Rights to READ-WRITE and READ-ONLY Response Codes
+
+   A particular ACL server implementation MAY allow "shared multiuser
+   access" to some mailboxes.  "Shared multiuser access" to a mailbox
+   means that multiple different users are able to access the same
+   mailbox, if they have proper access rights.  "Shared multiuser
+   access" to the mailbox doesn't mean that the ACL for the mailbox is
+   currently set to allow access by multiple users.  Let's denote a
+   "shared multiuser write access" as a "shared multiuser access" when a
+   user can be granted flag modification rights (any of "w", "s", or
+   "t").
+
+   Section 4 describes which rights are required for modifying different
+   flags.
+
+   If the ACL server implements some flags as shared for a mailbox
+   (i.e., the ACL for the mailbox MAY be set up so that changes to those
+   flags are visible to another user), let's call the set of rights
+   associated with these flags (as described in Section 4) for that
+   mailbox collectively as "shared flag rights".  Note that the "shared
+   flag rights" set MAY be different for different mailboxes.
+
+   If the server doesn't support "shared multiuser write access" to a
+   mailbox or doesn't implement shared flags on the mailbox, "shared
+   flag rights" for the mailbox is defined to be the empty set.
+
+   Example 1: Mailbox "banan" allows "shared multiuser write access" and
+              implements flags \Deleted, \Answered, and $MDNSent as
+              shared flags. "Shared flag rights" for the mailbox "banan"
+              is a set containing flags "t" (because system flag
+              \Deleted requires "t" right) and "w" (because both
+              \Answered and $MDNSent require "w" right).
+
+   Example 2: Mailbox "apple" allows "shared multiuser write access" and
+              implements \Seen system flag as shared flag. "Shared flag
+              rights" for the mailbox "apple" contains "s" right
+              because system flag \Seen requires "s" right.
+
+   Example 3: Mailbox "pear" allows "shared multiuser write access" and
+              implements flags \Seen, \Draft as shared flags. "Shared
+              flag rights" for the mailbox "apple" is a set containing
+              flags "s" (because system flag \Seen requires "s" right)
+              and "w" (because system flag \Draft requires "w" right).
+
+   The server MUST include a READ-ONLY response code in the tagged OK
+   response to a SELECT command if none of the following rights is
+   granted to the current user:
+
+
+
+
+Melnikov                    Standards Track                    [Page 19]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+    "i", "e", and "shared flag rights"(***).
+
+   The server SHOULD include a READ-WRITE response code in the tagged OK
+   response if at least one of the "i", "e", or "shared flag
+   rights"(***) is granted to the current user.
+
+   (***) Note that a future extension to this document can extend the
+   list of rights that causes the server to return the READ-WRITE
+   response code.
+
+   Example 1 (continued): The user that has "lrs" rights for the mailbox
+                          "banan".  The server returns READ-ONLY
+                          response code on SELECT, as none of "iewt"
+                          rights is granted to the user.
+
+   Example 2 (continued): The user that has "rit" rights for the mailbox
+                          "apple".  The server returns READ-WRITE
+                          response code on SELECT, as the user has "i"
+                          right.
+
+   Example 3 (continued): The user that has "rset" rights for the
+                          mailbox "pear".  The server returns READ-WRITE
+                          response code on SELECT, as the user has "e"
+                          and "s" rights.
+
+6.  Security Considerations
+
+   An implementation MUST make sure the ACL commands themselves do not
+   give information about mailboxes with appropriately restricted ACLs.
+   For example, when a user agent executes a GETACL command on a mailbox
+   that the user has no permission to LIST, the server would respond to
+   that request with the same error that would be used if the mailbox
+   did not exist, thus revealing no existence information, much less the
+   mailbox's ACL.
+
+   IMAP clients implementing ACL that are able to modify ACLs SHOULD
+   warn a user that wants to give full access (or even just the "a"
+   right) to the special identifier "anyone".
+
+   This document relies on [SASLprep] to describe steps required to
+   perform identifier canonicalization (preparation).  The preparation
+   algorithm in SASLprep was specifically designed such that its output
+   is canonical, and it is well-formed.  However, due to an anomaly
+   [PR29] in the specification of Unicode normalization, canonical
+   equivalence is not guaranteed for a select few character sequences.
+   Identifiers prepared with SASLprep can be stored and returned by an
+   ACL server.  The anomaly affects ACL manipulation and evaluation of
+   identifiers containing the selected character sequences.  These
+
+
+
+Melnikov                    Standards Track                    [Page 20]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   sequences, however, do not appear in well-formed text.  In order to
+   address this problem, an ACL server MAY reject identifiers containing
+   sequences described in [PR29] by sending the tagged BAD response.
+   This is in addition to the requirement to reject identifiers that
+   fail SASLprep preparation as described in Section 3.
+
+   Other security considerations described in [IMAP4] are relevant to
+   this document.  In particular, ACL information is sent in the clear
+   over the network unless confidentiality protection is negotiated.
+
+   This can be accomplished either by the use of STARTTLS, negotiated
+   privacy protection in the AUTHENTICATE command, or some other
+   protection mechanism.
+
+7.  Formal Syntax
+
+   Formal syntax is defined using ABNF [ABNF], extending the ABNF rules
+   in Section 9 of [IMAP4].  Elements not defined here can be found in
+   [ABNF] and [IMAP4].
+
+   Except as noted otherwise, all alphabetic characters are case
+   insensitive.  The use of uppercase or lowercase characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+   LOWER-ALPHA     =  %x61-7A   ;; a-z
+
+   acl-data        = "ACL" SP mailbox *(SP identifier SP
+                       rights)
+
+   capability      =/ rights-capa
+                       ;;capability is defined in [IMAP4]
+
+   command-auth    =/ setacl / deleteacl / getacl /
+                       listrights / myrights
+                       ;;command-auth is defined in [IMAP4]
+
+   deleteacl       = "DELETEACL" SP mailbox SP identifier
+
+   getacl          = "GETACL" SP mailbox
+
+   identifier      = astring
+
+   listrights      = "LISTRIGHTS" SP mailbox SP identifier
+
+   listrights-data = "LISTRIGHTS" SP mailbox SP identifier
+                           SP rights *(SP rights)
+
+
+
+
+Melnikov                    Standards Track                    [Page 21]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   mailbox-data    =/ acl-data / listrights-data / myrights-data
+                       ;;mailbox-data is defined in [IMAP4]
+
+   mod-rights      = astring
+                       ;; +rights to add, -rights to remove
+                       ;; rights to replace
+
+   myrights        = "MYRIGHTS" SP mailbox
+
+   myrights-data   = "MYRIGHTS" SP mailbox SP rights
+
+   new-rights      = 1*LOWER-ALPHA
+                       ;; MUST include "t", "e", "x", and "k".
+                       ;; MUST NOT include standard rights listed
+                       ;; in section 2.2
+
+   rights          = astring
+                       ;; only lowercase ASCII letters and digits
+                       ;; are allowed.
+
+   rights-capa     = "RIGHTS=" new-rights
+                       ;; RIGHTS=... capability
+
+   setacl          = "SETACL" SP mailbox SP identifier
+                       SP mod-rights
+
+8.  IANA Considerations
+
+   IMAP4 capabilities are registered by publishing a standards-track or
+   IESG-approved experimental RFC.  The registry is currently located
+   at:
+
+      http://www.iana.org/assignments/imap4-capabilities
+
+   This document defines the RIGHTS= IMAP capability.  IANA has added
+   this capability to the registry.
+
+9.  Internationalization Considerations
+
+   Section 3 states requirements on servers regarding
+   internationalization of identifiers.
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 22]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+Appendix A.  Changes since RFC 2086
+
+   1.   Changed the charset of "identifier" from US-ASCII to UTF-8.
+   2.   Specified that mailbox deletion is controlled by the "x" right
+        and EXPUNGE is controlled by the "e" right.
+   3.   Added the "t" right that controls STORE \Deleted.  Redefined the
+        "d" right to be a macro for "e", "t", and possibly "x".
+   4.   Added the "k" right that controls CREATE.  Redefined the "c"
+        right to be a macro for "k" and possibly "x".
+   5.   Specified that the "a" right also controls DELETEACL.
+   6.   Specified that the "r" right also controls STATUS.
+   7.   Removed the requirement to check the "r" right for CHECK, SEARCH
+        and FETCH, as this is required for SELECT/EXAMINE to be
+        successful.
+   8.   LISTRIGHTS requires the "a" right on the mailbox (same as
+        SETACL).
+   9.   Deleted "PARTIAL", this is a deprecated feature of RFC 1730.
+   10.  Specified that the "w" right controls setting flags other than
+        \Seen and \Deleted on APPEND.  Also specified that the "s" right
+        controls the \Seen flag and that the "t" right controls the
+        \Deleted flag.
+   11.  Specified that SUBSCRIBE is NOT allowed with the "r" right.
+   12.  Specified that the "l" right controls SUBSCRIBE.
+   13.  GETACL is NOT allowed with the "r" right, even though there are
+        several implementations that allows that.  If a user only has
+        "r" right, GETACL can disclose information about identifiers
+        existing on the mail system.
+   14.  Clarified that RENAME requires the "k" right for the new parent
+        and the "x" right for the old name.
+   15.  Added new section that describes which rights are required
+        and/or checked when performing various IMAP commands.
+   16.  Added mail client security considerations when dealing with
+        special identifier "anyone".
+   17.  Clarified that negative rights are not the same as DELETEACL.
+   18.  Added "Compatibility with RFC 2086" section.
+   19.  Added section about mapping of ACL rights to READ-WRITE and
+        READ-ONLY response codes.
+   20.  Changed BNF to ABNF.
+   21.  Added "Implementation Notes" section.
+   22.  Updated "References" section.
+   23.  Added more examples.
+   24.  Clarified when the virtual "c" and "d" rights are returned in
+        ACL, MYRIGHTS, and LISTRIGHTS responses.
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 23]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+Appendix B.  Compatibility with RFC 2086
+
+   This non-normative section gives guidelines as to how an existing RFC
+   2086 server implementation may be updated to comply with this
+   document.
+
+   This document splits the "d" right into several new different rights:
+   "t", "e", and possibly "x" (see Section 2.1.1 for more details).  The
+   "d" right remains for backward-compatibility, but it is a virtual
+   right.  There are two approaches for RFC 2086 server implementors to
+   handle the "d" right and the new rights that have replaced it:
+
+   a.  Tie "t", "e" (and possibly "x) together - almost no changes.
+   b.  Implement separate "x", "t" and "e".  Return the "d" right in a
+       MYRIGHTS response or an ACL response containing ACL information
+       when any of the "t", "e" (and "x") is granted.
+
+   In a similar manner this document splits the "c" right into several
+   new different rights: "k" and possibly "x" (see Section 2.1.1 for
+   more details).  The "c" right remains for backwards-compatibility but
+   it is a virtual right.  Again, RFC 2086 server implementors can
+   choose to tie rights or to implement separate rights, as described
+   above.
+
+   Also check Sections 5.1.1 and 5.1.2, as well as Appendix A, to see
+   other changes required.  Server implementors should check which
+   rights are required to invoke different IMAP4 commands as described
+   in Section 4.
+
+Appendix C.  Known Deficiencies
+
+   This specification has some known deficiencies including:
+
+   1.  This is inadequate to provide complete read-write access to
+       mailboxes protected by Unix-style rights bits because there is no
+       equivalent to "chown" and "chgrp" commands nor is there a good
+       way to discover such limitations are present.
+   2.  Because this extension leaves the specific semantics of how
+       rights are combined by the server as implementation defined, the
+       ability to build a user-friendly interface is limited.
+   3.  Users, groups, and special identifiers (e.g., anyone) exist in
+       the same namespace.
+
+   The work-in-progress "ACL2" extension is intended to redesign this
+   extension to address these deficiencies without the constraint of
+   backward-compatibility and may eventually supercede this facility.
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 24]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+   However, RFC 2086 is deployed in multiple implementations so this
+   intermediate step, which fixes the straightforward deficiencies in a
+   backward-compatible fashion, is considered worthwhile.
+
+Appendix D.  Acknowledgements
+
+   This document is a revision of RFC 2086 written by John G. Myers.
+
+   Editor appreciates comments received from Mark Crispin, Chris Newman,
+   Cyrus Daboo, John G. Myers, Dave Cridland, Ken Murchison, Steve Hole,
+   Vladimir Butenko, Larry Greenfield, Robert Siemborski, Harrie
+   Hazewinkel, Philip Guenther, Brian Candler, Curtis King, Lyndon
+   Nerenberg, Lisa Dusseault, Arnt Gulbrandsen, and other participants
+   of the IMAPEXT working group.
+
+Normative References
+
+   [KEYWORDS]   Bradner, S., "Key words for use in RFCs to Indicate
+                Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [ABNF]       Crocker, D. and P. Overell, "Augmented BNF for Syntax
+                Specifications: ABNF", RFC 4234, October 2005.
+
+   [IMAP4]      Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+                4rev1", RFC 3501, March 2003.
+
+   [UTF-8]      Yergeau, F., "UTF-8, a transformation format of ISO
+                10646", STD 63, RFC 3629, November 2003.
+
+   [Stringprep] Hoffman, P. and M. Blanchet, "Preparation of
+                Internationalized Strings ("stringprep")", RFC 3454,
+                December 2002.
+
+   [SASLprep]   Zeilenga, K., "SASLprep: Stringprep Profile for User
+                Names and Passwords", RFC 4013, February 2005.
+
+Informative References
+
+   [RFC2086]    Myers, J., "IMAP4 ACL extension", RFC 2086,
+                January 1997.
+
+   [PR29]       "Public Review Issue #29: Normalization Issue",
+                February 2004,
+                <http://www.unicode.org/review/pr-29.html>.
+
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 25]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+Author's Address
+
+   Alexey Melnikov
+   Isode Ltd.
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex  TW12 2BX
+   GB
+
+   EMail: alexey.melnikov@isode.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 26]
+
+RFC 4314                        IMAP ACL                   December 2005
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2005).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at ietf-
+   ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+Melnikov                    Standards Track                    [Page 27]
+
diff --git a/imap/docs/rfc/rfc4315.txt b/imap/docs/rfc/rfc4315.txt
new file mode 100644
index 00000000..c026f422
--- /dev/null
+++ b/imap/docs/rfc/rfc4315.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 4315                                 December 2005
+Obsoletes: 2359
+Category: Standards Track
+
+
+      Internet Message Access Protocol (IMAP) - UIDPLUS extension
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2005).
+
+Abstract
+
+   The UIDPLUS extension of the Internet Message Access Protocol (IMAP)
+   provides a set of features intended to reduce the amount of time and
+   resources used by some client operations.  The features in UIDPLUS
+   are primarily intended for disconnected-use clients.
+
+1.  Introduction and Overview
+
+   The UIDPLUS extension is present in any IMAP server implementation
+   that returns "UIDPLUS" as one of the supported capabilities to the
+   CAPABILITY command.
+
+   The UIDPLUS extension defines an additional command.  In addition,
+   this document recommends new status response codes in IMAP that
+   SHOULD be returned by all server implementations, regardless of
+   whether or not the UIDPLUS extension is implemented.
+
+   The added facilities of the features in UIDPLUS are optimizations;
+   clients can provide equivalent functionality, albeit less
+   efficiently, by using facilities in the base protocol.
+
+1.1.  Conventions Used in This Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.
+
+
+
+
+
+Crispin                     Standards Track                     [Page 1]
+
+RFC 4315                IMAP - UIDPLUS Extension           December 2005
+
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
+   be interpreted as described in [KEYWORDS].
+
+   A "UID set" is similar to the [IMAP] sequence set; however, the "*"
+   value for a sequence number is not permitted.
+
+2.  Additional Commands
+
+   The following command definition is an extension to [IMAP] section
+   6.4.
+
+2.1.  UID EXPUNGE Command
+
+   Arguments:  sequence set
+
+   Data:       untagged responses: EXPUNGE
+
+   Result:     OK - expunge completed
+               NO - expunge failure (e.g., permission denied)
+               BAD - command unknown or arguments invalid
+
+      The UID EXPUNGE command permanently removes all messages that both
+      have the \Deleted flag set and have a UID that is included in the
+      specified sequence set from the currently selected mailbox.  If a
+      message either does not have the \Deleted flag set or has a UID
+      that is not included in the specified sequence set, it is not
+      affected.
+
+      This command is particularly useful for disconnected use clients.
+      By using UID EXPUNGE instead of EXPUNGE when resynchronizing with
+      the server, the client can ensure that it does not inadvertantly
+      remove any messages that have been marked as \Deleted by other
+      clients between the time that the client was last connected and
+      the time the client resynchronizes.
+
+      If the server does not support the UIDPLUS capability, the client
+      should fall back to using the STORE command to temporarily remove
+      the \Deleted flag from messages it does not want to remove, then
+      issuing the EXPUNGE command.  Finally, the client should use the
+      STORE command to restore the \Deleted flag on the messages in
+      which it was temporarily removed.
+
+      Alternatively, the client may fall back to using just the EXPUNGE
+      command, risking the unintended removal of some messages.
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 2]
+
+RFC 4315                IMAP - UIDPLUS Extension           December 2005
+
+
+   Example:    C: A003 UID EXPUNGE 3000:3002
+               S: * 3 EXPUNGE
+               S: * 3 EXPUNGE
+               S: * 3 EXPUNGE
+               S: A003 OK UID EXPUNGE completed
+
+3.  Additional Response Codes
+
+   The following response codes are extensions to the response codes
+   defined in [IMAP] section 7.1.  With limited exceptions, discussed
+   below, server implementations that advertise the UIDPLUS extension
+   SHOULD return these response codes.
+
+   In the case of a mailbox that has permissions set so that the client
+   can COPY or APPEND to the mailbox, but not SELECT or EXAMINE it, the
+   server SHOULD NOT send an APPENDUID or COPYUID response code as it
+   would disclose information about the mailbox.
+
+   In the case of a mailbox that has UIDNOTSTICKY status (as defined
+   below), the server MAY omit the APPENDUID or COPYUID response code as
+   it is not meaningful.
+
+   If the server does not return the APPENDUID or COPYUID response
+   codes, the client can discover this information by selecting the
+   destination mailbox.  The location of messages placed in the
+   destination mailbox by COPY or APPEND can be determined by using
+   FETCH and/or SEARCH commands (e.g., for Message-ID or some unique
+   marker placed in the message in an APPEND).
+
+   APPENDUID
+
+      Followed by the UIDVALIDITY of the destination mailbox and the UID
+      assigned to the appended message in the destination mailbox,
+      indicates that the message has been appended to the destination
+      mailbox with that UID.
+
+      If the server also supports the [MULTIAPPEND] extension, and if
+      multiple messages were appended in the APPEND command, then the
+      second value is a UID set containing the UIDs assigned to the
+      appended messages, in the order they were transmitted in the
+      APPEND command.  This UID set may not contain extraneous UIDs or
+      the symbol "*".
+
+         Note: the UID set form of the APPENDUID response code MUST NOT
+         be used if only a single message was appended.  In particular,
+         a server MUST NOT send a range such as 123:123.  This is
+         because a client that does not support [MULTIAPPEND] expects
+         only a single UID and not a UID set.
+
+
+
+Crispin                     Standards Track                     [Page 3]
+
+RFC 4315                IMAP - UIDPLUS Extension           December 2005
+
+
+      UIDs are assigned in strictly ascending order in the mailbox
+      (refer to [IMAP], section 2.3.1.1) and UID ranges are as in
+      [IMAP]; in particular, note that a range of 12:10 is exactly
+      equivalent to 10:12 and refers to the sequence 10,11,12.
+
+      This response code is returned in a tagged OK response to the
+      APPEND command.
+
+   COPYUID
+
+      Followed by the UIDVALIDITY of the destination mailbox, a UID set
+      containing the UIDs of the message(s) in the source mailbox that
+      were copied to the destination mailbox and containing the UIDs
+      assigned to the copied message(s) in the destination mailbox,
+      indicates that the message(s) have been copied to the destination
+      mailbox with the stated UID(s).
+
+      The source UID set is in the order the message(s) were copied; the
+      destination UID set corresponds to the source UID set and is in
+      the same order.  Neither of the UID sets may contain extraneous
+      UIDs or the symbol "*".
+
+      UIDs are assigned in strictly ascending order in the mailbox
+      (refer to [IMAP], section 2.3.1.1) and UID ranges are as in
+      [IMAP]; in particular, note that a range of 12:10 is exactly
+      equivalent to 10:12 and refers to the sequence 10,11,12.
+
+      This response code is returned in a tagged OK response to the COPY
+      command.
+
+   UIDNOTSTICKY
+
+      The selected mailbox is supported by a mail store that does not
+      support persistent UIDs; that is, UIDVALIDITY will be different
+      each time the mailbox is selected.  Consequently, APPEND or COPY
+      to this mailbox will not return an APPENDUID or COPYUID response
+      code.
+
+      This response code is returned in an untagged NO response to the
+      SELECT command.
+
+         Note: servers SHOULD NOT have any UIDNOTSTICKY mail stores.
+         This facility exists to support legacy mail stores in which it
+         is technically infeasible to support persistent UIDs.  This
+         should be avoided when designing new mail stores.
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 4]
+
+RFC 4315                IMAP - UIDPLUS Extension           December 2005
+
+
+   Example:    C: A003 APPEND saved-messages (\Seen) {297}
+               C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+               C: From: Fred Foobar <foobar@example.com>
+               C: Subject: afternoon meeting
+               C: To: mooch@example.com
+               C: Message-Id: <B27397-0100000@example.com>
+               C: MIME-Version: 1.0
+               C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+               C:
+               C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+               C:
+               S: A003 OK [APPENDUID 38505 3955] APPEND completed
+               C: A004 COPY 2:4 meeting
+               S: A004 OK [COPYUID 38505 304,319:320 3956:3958] Done
+               C: A005 UID COPY 305:310 meeting
+               S: A005 OK No matching messages, so nothing copied
+               C: A006 COPY 2 funny
+               S: A006 OK Done
+               C: A007 SELECT funny
+               S: * 1 EXISTS
+               S: * 1 RECENT
+               S: * OK [UNSEEN 1] Message 1 is first unseen
+               S: * OK [UIDVALIDITY 3857529045] Validity session-only
+               S: * OK [UIDNEXT 2] Predicted next UID
+               S: * NO [UIDNOTSTICKY] Non-persistent UIDs
+               S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+               S: * OK [PERMANENTFLAGS (\Deleted \Seen)] Limited
+               S: A007 OK [READ-WRITE] SELECT completed
+
+   In this example, A003 and A004 demonstrate successful appending and
+   copying to a mailbox that returns the UIDs assigned to the messages.
+   A005 is an example in which no messages were copied; this is because
+   in A003, we see that message 2 had UID 304, and message 3 had UID
+   319; therefore, UIDs 305 through 310 do not exist (refer to section
+   2.3.1.1 of [IMAP] for further explanation).  A006 is an example of a
+   message being copied that did not return a COPYUID; and, as expected,
+   A007 shows that the mail store containing that mailbox does not
+   support persistent UIDs.
+
+4.  Formal Syntax
+
+   Formal syntax is defined using ABNF [ABNF], which extends the ABNF
+   rules defined in [IMAP].  The IMAP4 ABNF should be imported before
+   attempting to validate these rules.
+
+   append-uid      = uniqueid
+
+   capability      =/ "UIDPLUS"
+
+
+
+Crispin                     Standards Track                     [Page 5]
+
+RFC 4315                IMAP - UIDPLUS Extension           December 2005
+
+
+   command-select  =/ uid-expunge
+
+   resp-code-apnd  = "APPENDUID" SP nz-number SP append-uid
+
+   resp-code-copy  = "COPYUID" SP nz-number SP uid-set SP uid-set
+
+   resp-text-code  =/ resp-code-apnd / resp-code-copy / "UIDNOTSTICKY"
+                     ; incorporated before the expansion rule of
+                     ;  atom [SP 1*<any TEXT-CHAR except "]">]
+                     ; that appears in [IMAP]
+
+   uid-expunge     = "UID" SP "EXPUNGE" SP sequence-set
+
+   uid-set         = (uniqueid / uid-range) *("," uid-set)
+
+   uid-range       = (uniqueid ":" uniqueid)
+                     ; two uniqueid values and all values
+                     ; between these two regards of order.
+                     ; Example: 2:4 and 4:2 are equivalent.
+
+   Servers that support [MULTIAPPEND] will have the following extension
+   to the above rules:
+
+   append-uid      =/ uid-set
+                     ; only permitted if client uses [MULTIAPPEND]
+                     ; to append multiple messages.
+
+5.  Security Considerations
+
+   The COPYUID and APPENDUID response codes return information about the
+   mailbox, which may be considered sensitive if the mailbox has
+   permissions set that permit the client to COPY or APPEND to the
+   mailbox, but not SELECT or EXAMINE it.
+
+   Consequently, these response codes SHOULD NOT be issued if the client
+   does not have access to SELECT or EXAMINE the mailbox.
+
+6.  IANA Considerations
+
+   This document constitutes registration of the UIDPLUS capability in
+   the imap4-capabilities registry, replacing [RFC2359].
+
+7.  Normative References
+
+   [ABNF]        Crocker, D. and P. Overell, "Augmented BNF for Syntax
+                 Specifications: ABNF", RFC 4234, October 2005.
+
+
+
+
+
+Crispin                     Standards Track                     [Page 6]
+
+RFC 4315                IMAP - UIDPLUS Extension           December 2005
+
+
+   [IMAP]        Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+                 VERSION 4rev1", RFC 3501, March 2003.
+
+   [KEYWORDS]    Bradner, S., "Key words for use in RFCs to Indicate
+                 Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [MULTIAPPEND] Crispin, M., "Internet Message Access Protocol (IMAP) -
+                 MULTIAPPEND Extension", RFC 3502, March 2003.
+
+8.  Informative References
+
+   [RFC2359]     Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June
+                 1998.
+
+9.  Changes from RFC 2359
+
+   This document obsoletes [RFC2359].  However, it is based upon that
+   document, and takes substantial text from it (albeit with numerous
+   clarifications in wording).
+
+   [RFC2359] implied that a server must always return COPYUID/APPENDUID
+   data; thus suggesting that in such cases the server should return
+   arbitrary data if the destination mailbox did not support persistent
+   UIDs.  This document adds the UIDNOTSTICKY response code to indicate
+   that a mailbox does not support persistent UIDs, and stipulates that
+   a UIDPLUS server does not return COPYUID/APPENDUID data when the COPY
+   (or APPEND) destination mailbox has UIDNOTSTICKY status.
+
+Author's Address
+
+   Mark R. Crispin
+   Networks and Distributed Computing
+   University of Washington
+   4545 15th Avenue NE
+   Seattle, WA  98105-4527
+
+   Phone: (206) 543-5762
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 7]
+
+RFC 4315                IMAP - UIDPLUS Extension           December 2005
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2005).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at ietf-
+   ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 8]
+
diff --git a/imap/docs/rfc/rfc4422.txt b/imap/docs/rfc/rfc4422.txt
new file mode 100644
index 00000000..049fa8c5
--- /dev/null
+++ b/imap/docs/rfc/rfc4422.txt
@@ -0,0 +1,1851 @@
+
+
+
+
+
+
+Network Working Group                                   A. Melnikov, Ed.
+Request for Comments: 4422                                 Isode Limited
+Obsoletes: 2222                                         K. Zeilenga, Ed.
+Category: Standards Track                            OpenLDAP Foundation
+                                                               June 2006
+
+
+            Simple Authentication and Security Layer (SASL)
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   The Simple Authentication and Security Layer (SASL) is a framework
+   for providing authentication and data security services in
+   connection-oriented protocols via replaceable mechanisms.  It
+   provides a structured interface between protocols and mechanisms.
+   The resulting framework allows new protocols to reuse existing
+   mechanisms and allows old protocols to make use of new mechanisms.
+   The framework also provides a protocol for securing subsequent
+   protocol exchanges within a data security layer.
+
+   This document describes how a SASL mechanism is structured, describes
+   how protocols include support for SASL, and defines the protocol for
+   carrying a data security layer over a connection.  In addition, this
+   document defines one SASL mechanism, the EXTERNAL mechanism.
+
+   This document obsoletes RFC 2222.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 1]
+
+RFC 4422                          SASL                         June 2006
+
+
+Table of Contents
+
+   1. Introduction ....................................................3
+      1.1. Document Audiences .........................................4
+      1.2. Relationship to Other Documents ............................4
+      1.3. Conventions ................................................5
+   2. Identity Concepts ...............................................5
+   3. The Authentication Exchange .....................................6
+      3.1. Mechanism Naming ...........................................8
+      3.2. Mechanism Negotiation ......................................9
+      3.3. Request Authentication Exchange ............................9
+      3.4. Challenges and Responses ...................................9
+           3.4.1. Authorization Identity String ......................10
+      3.5. Aborting Authentication Exchanges .........................10
+      3.6. Authentication Outcome ....................................11
+      3.7. Security Layers ...........................................12
+      3.8. Multiple Authentications ..................................12
+   4. Protocol Requirements ..........................................13
+   5. Mechanism Requirements .........................................16
+   6. Security Considerations ........................................18
+      6.1. Active Attacks ............................................19
+           6.1.1. Hijack Attacks .....................................19
+           6.1.2. Downgrade Attacks ..................................19
+           6.1.3. Replay Attacks .....................................20
+           6.1.4. Truncation Attacks .................................20
+           6.1.5. Other Active Attacks ...............................20
+      6.2. Passive Attacks ...........................................20
+      6.3. Re-keying .................................................21
+      6.4. Other Considerations ......................................21
+   7. IANA Considerations ............................................22
+      7.1. SASL Mechanism Registry ...................................22
+      7.2. Registration Changes ......................................26
+   8. References .....................................................26
+      8.1. Normative References ......................................26
+      8.2. Informative References ....................................27
+   9. Acknowledgements ...............................................28
+   Appendix A.  The SASL EXTERNAL Mechanism ..........................29
+      A.1. EXTERNAL Technical Specification ..........................29
+      A.2. SASL EXTERNAL Examples ....................................30
+      A.3. Security Considerations ...................................31
+   Appendix B.  Changes since RFC 2222 ...............................31
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 2]
+
+RFC 4422                          SASL                         June 2006
+
+
+1.  Introduction
+
+   The Simple Authentication and Security Layer (SASL) is a framework
+   for providing authentication and data security services in
+   connection-oriented protocols via replaceable mechanisms.  SASL
+   provides a structured interface between protocols and mechanisms.
+   SASL also provides a protocol for securing subsequent protocol
+   exchanges within a data security layer.  The data security layer can
+   provide data integrity, data confidentiality, and other services.
+
+   SASL's design is intended to allow new protocols to reuse existing
+   mechanisms without requiring redesign of the mechanisms and allows
+   existing protocols to make use of new mechanisms without redesign of
+   protocols.
+
+   SASL is conceptually a framework that provides an abstraction layer
+   between protocols and mechanisms as illustrated in the following
+   diagram.
+
+                  SMTP    LDAP    XMPP   Other protocols ...
+                     \       |    |      /
+                      \      |    |     /
+                     SASL abstraction layer
+                      /      |    |     \
+                     /       |    |      \
+              EXTERNAL   GSSAPI  PLAIN   Other mechanisms ...
+
+   It is through the interfaces of this abstraction layer that the
+   framework allows any protocol to utilize any mechanism.  While this
+   layer does generally hide the particulars of protocols from
+   mechanisms and the particulars of mechanisms from protocols, this
+   layer does not generally hide the particulars of mechanisms from
+   protocol implementations.  For example, different mechanisms require
+   different information to operate, some of them use password-based
+   authentication, some of then require realm information, others make
+   use of Kerberos tickets, certificates, etc.  Also, in order to
+   perform authorization, server implementations generally have to
+   implement identity mapping between authentication identities, whose
+   form is mechanism specific, and authorization identities, whose form
+   is application protocol specific.  Section 2 discusses identity
+   concepts.
+
+   It is possible to design and implement this framework in ways that do
+   abstract away particulars of similar mechanisms.  Such a framework
+   implementation, as well as mechanisms implementations, could be
+   designed not only to be shared by multiple implementations of a
+   particular protocol but to be shared by implementations of multiple
+   protocols.
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 3]
+
+RFC 4422                          SASL                         June 2006
+
+
+   The framework incorporates interfaces with both protocols and
+   mechanisms in which authentication exchanges are carried out.
+   Section 3 discusses SASL authentication exchanges.
+
+   To use SASL, each protocol (amongst other items) provides a method
+   for identifying which mechanism is to be used, a method for exchange
+   of mechanism-specific server-challenges and client-responses, and a
+   method for communicating the outcome of the authentication exchange.
+   Section 4 discusses SASL protocol requirements.
+
+   Each SASL mechanism defines (amongst other items) a series of
+   server-challenges and client-responses that provide authentication
+   services and negotiate data security services.  Section 5 discusses
+   SASL mechanism requirements.
+
+   Section 6 discusses security considerations.  Section 7 discusses
+   IANA considerations.  Appendix A defines the SASL EXTERNAL mechanism.
+
+1.1.  Document Audiences
+
+   This document is written to serve several different audiences:
+
+      -  protocol designers using this specification to support
+         authentication in their protocol,
+
+      -  mechanism designers that define new SASL mechanisms, and
+
+      -  implementors of clients or servers for those protocols that
+         support SASL.
+
+   While the document organization is intended to allow readers to focus
+   on details relevant to their engineering, readers are encouraged to
+   read and understand all aspects of this document.
+
+1.2.  Relationship to Other Documents
+
+   This document obsoletes RFC 2222.  It replaces all portions of RFC
+   2222 excepting sections 7.1 (the KERBEROS_IV mechanism), 7.2 (the
+   GSSAPI mechanism), 7.3 (the SKEY mechanism).  The KERBEROS_IV and
+   SKEY mechanisms are now viewed as obsolete and their specifications
+   provided in RFC 2222 are Historic.  The GSSAPI mechanism is now
+   separately specified [SASL-GSSAPI].
+
+   Appendix B provides a summary of changes since RFC 2222.
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 4]
+
+RFC 4422                          SASL                         June 2006
+
+
+1.3.  Conventions
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in BCP 14 [RFC2119].
+
+   Character names in this document use the notation for code points and
+   names from the Unicode Standard [Unicode].  For example, the letter
+   "a" may be represented as either <U+0061> or <LATIN SMALL LETTER A>.
+
+   Note: a glossary of terms used in Unicode can be found in [Glossary].
+   Information on the Unicode character encoding model can be found in
+   [CharModel].
+
+   In examples, "C:" and "S:" indicate lines of data to be sent by the
+   client and server, respectively.  Lines have been wrapped for
+   improved readability.
+
+2.  Identity Concepts
+
+   In practice, authentication and authorization may involve multiple
+   identities, possibly in different forms (simple username, Kerberos
+   principal, X.500 Distinguished Name, etc.), possibly with different
+   representations (e.g., ABNF-described UTF-8 encoded Unicode character
+   string, BER-encoded Distinguished Name).  While technical
+   specifications often prescribe both the identity form and
+   representation used on the network, different identity forms and/or
+   representations may be (and often are) used within implementations.
+   How identities of different forms relate to each other is, generally,
+   a local matter.  In addition, the forms and representations used
+   within an implementation are a local matter.
+
+   However, conceptually, the SASL framework involves two identities:
+
+      1) an identity associated with the authentication credentials
+         (termed the authentication identity), and
+
+      2) an identity to act as (termed the authorization identity).
+
+   SASL mechanism specifications describe the credential form(s) (e.g.,
+   X.509 certificates, Kerberos tickets, simple username/password) used
+   to authenticate the client, including (where appropriate) the syntax
+   and semantics of authentication identities carried in the
+   credentials.  SASL protocol specifications describe the identity
+   form(s) used in authorization and, in particular, prescribe the
+   syntax and semantics of the authorization identity character string
+   to be transferred by mechanisms.
+
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 5]
+
+RFC 4422                          SASL                         June 2006
+
+
+   The client provides its credentials (which include or imply an
+   authentication identity) and, optionally, a character string
+   representing the requested authorization identity as part of the SASL
+   exchange.  When this character string is omitted or empty, the client
+   is requesting to act as the identity associated with the credentials
+   (e.g., the user is requesting to act as the authentication identity).
+
+   The server is responsible for verifying the client's credentials and
+   verifying that the identity it associates with the client's
+   credentials (e.g., the authentication identity) is allowed to act as
+   the authorization identity.  A SASL exchange fails if either (or
+   both) of these verifications fails.  (The SASL exchange may fail for
+   other reasons, such as service authorization failure.)
+
+   However, the precise form(s) of the authentication identities (used
+   within the server in its verifications, or otherwise) and the precise
+   form(s) of the authorization identities (used in making authorization
+   decisions, or otherwise) are beyond the scope of SASL and this
+   specification.  In some circumstances, the precise identity forms
+   used in some context outside of the SASL exchange may be dictated by
+   other specifications.  For instance, an identity assumption
+   authorization (proxy authorization) policy specification may dictate
+   how authentication and authorization identities are represented in
+   policy statements.
+
+3.  The Authentication Exchange
+
+   Each authentication exchange consists of a message from the client to
+   the server requesting authentication via a particular mechanism,
+   followed by one or more pairs of challenges from the server and
+   responses from the client, followed by a message from the server
+   indicating the outcome of the authentication exchange.  (Note:
+   exchanges may also be aborted as discussed in Section 3.5.)
+
+   The following illustration provides a high-level overview of an
+   authentication exchange.
+
+      C: Request authentication exchange
+      S: Initial challenge
+      C: Initial response
+      <additional challenge/response messages>
+      S: Outcome of authentication exchange
+
+   If the outcome is successful and a security layer was negotiated,
+   this layer is then installed (see Section 3.7).  This also applies to
+   the following illustrations.
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 6]
+
+RFC 4422                          SASL                         June 2006
+
+
+   Some mechanisms specify that the first data sent in the
+   authentication exchange is from the client to the server.  Protocols
+   may provide an optional initial response field in the request message
+   to carry this data.  Where the mechanism specifies that the first
+   data sent in the exchange is from the client to the server, the
+   protocol provides an optional initial response field, and the client
+   uses this field, the exchange is shortened by one round-trip:
+
+      C: Request authentication exchange + Initial response
+      <additional challenge/response messages>
+      S: Outcome of authentication exchange
+
+   Where the mechanism specifies that the first data sent in the
+   exchange is from the client to the server and this field is
+   unavailable or unused, the client request is followed by an empty
+   challenge.
+
+      C: Request authentication exchange
+      S: Empty Challenge
+      C: Initial Response
+      <additional challenge/response messages>
+      S: Outcome of authentication exchange
+
+   Should a client include an initial response in its request where the
+   mechanism does not allow the client to send data first, the
+   authentication exchange fails.
+
+   Some mechanisms specify that the server is to send additional data to
+   the client when indicating a successful outcome.  Protocols may
+   provide an optional additional data field in the outcome message to
+   carry this data.  Where the mechanism specifies that the server is to
+   return additional data with the successful outcome, the protocol
+   provides an optional additional data field in the outcome message,
+   and the server uses this field, the exchange is shortened by one
+   round-trip:
+
+      C: Request authentication exchange
+      S: Initial challenge
+      C: Initial response
+      <additional challenge/response messages>
+      S: Outcome of authentication exchange with
+         additional data with success
+
+   Where the mechanism specifies that the server is to return additional
+   data to the client with a successful outcome and this field is
+   unavailable or unused, the additional data is sent as a challenge
+   whose response is empty.  After receiving this response, the server
+   then indicates the successful outcome.
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 7]
+
+RFC 4422                          SASL                         June 2006
+
+
+      C: Request authentication exchange
+      S: Initial challenge
+      C: Initial response
+      <additional challenge/response messages>
+      S: Additional data challenge
+      C: Empty Response
+      S: Outcome of authentication exchange
+
+   Where mechanisms specify that the first data sent in the exchange is
+   from the client to the server and additional data is sent to the
+   client along with indicating a successful outcome, and the protocol
+   provides fields supporting both, then the exchange takes two fewer
+   round-trips:
+
+      C: Request authentication exchange + Initial response
+      <additional challenge/response messages>
+      S: Outcome of authentication exchange
+         with additional data with success
+
+   instead of:
+
+      C: Request authentication exchange
+      S: Empty Challenge
+      C: Initial Response
+      <additional challenge/response messages>
+      S: Additional data challenge
+      C: Empty Response
+      S: Outcome of authentication exchange
+
+3.1.  Mechanism Naming
+
+   SASL mechanisms are named by character strings, from 1 to 20
+   characters in length, consisting of ASCII [ASCII] uppercase letters,
+   digits, hyphens, and/or underscores.  In the following Augmented
+   Backus-Naur Form (ABNF) [RFC4234] grammar, the <sasl-mech> production
+   defines the syntax of a SASL mechanism name.
+
+      sasl-mech    = 1*20mech-char
+      mech-char    = UPPER-ALPHA / DIGIT / HYPHEN / UNDERSCORE
+      ; mech-char is restricted to A-Z (uppercase only), 0-9, -, and _
+      ; from ASCII character set.
+
+      UPPER-ALPHA  = %x41-5A  ; A-Z (uppercase only)
+      DIGIT        = %x30-39  ; 0-9
+      HYPHEN       = %x2D ; hyphen (-)
+      UNDERSCORE   = %x5F ; underscore (_)
+
+   SASL mechanism names are registered as discussed in Section 7.1.
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 8]
+
+RFC 4422                          SASL                         June 2006
+
+
+3.2.  Mechanism Negotiation
+
+   Mechanism negotiation is protocol specific.
+
+   Commonly, a protocol will specify that the server advertises
+   supported and available mechanisms to the client via some facility
+   provided by the protocol, and the client will then select the "best"
+   mechanism from this list that it supports and finds suitable.
+
+   Note that the mechanism negotiation is not protected by the
+   subsequent authentication exchange and hence is subject to downgrade
+   attacks if not protected by other means.
+
+   To detect downgrade attacks, a protocol can allow the client to
+   discover available mechanisms subsequent to the authentication
+   exchange and installation of data security layers with at least data
+   integrity protection.  This allows the client to detect changes to
+   the list of mechanisms supported by the server.
+
+3.3.  Request Authentication Exchange
+
+   The authentication exchange is initiated by the client by requesting
+   authentication via a mechanism it specifies.  The client sends a
+   message that contains the name of the mechanism to the server.  The
+   particulars of the message are protocol specific.
+
+   Note that the name of the mechanism is not protected by the
+   mechanism, and hence is subject to alteration by an attacker if not
+   integrity protected by other means.
+
+   Where the mechanism is defined to allow the client to send data
+   first, and the protocol's request message includes an optional
+   initial response field, the client may include the response to the
+   initial challenge in the authentication request message.
+
+3.4.  Challenges and Responses
+
+   The authentication exchange involves one or more pairs of server-
+   challenges and client-responses, the particulars of which are
+   mechanism specific.  These challenges and responses are enclosed in
+   protocol messages, the particulars of which are protocol specific.
+
+   Through these challenges and responses, the mechanism may:
+
+      -  authenticate the client to the server,
+
+      -  authenticate the server to the client,
+
+
+
+
+Melnikov & Zeilenga         Standards Track                     [Page 9]
+
+RFC 4422                          SASL                         June 2006
+
+
+      -  transfer an authorization identity string,
+
+      -  negotiate a security layer, and
+
+      -  provide other services.
+
+   The negotiation of the security layer may involve negotiation of the
+   security services to be provided in the layer, how these services
+   will be provided, and negotiation of a maximum cipher-text buffer
+   size each side is able to receive in the layer (see Section 3.6).
+
+   After receiving an authentication request or any client response, the
+   server may issue a challenge, abort the exchange, or indicate the
+   outcome of an exchange.  After receiving a challenge, a client
+   mechanism may issue a response or abort the exchange.
+
+3.4.1.  Authorization Identity String
+
+   The authorization identity string is a sequence of zero or more
+   Unicode [Unicode] characters, excluding the NUL (U+0000) character,
+   representing the identity to act as.
+
+   If the authorization identity string is absent, the client is
+   requesting to act as the identity the server associates with the
+   client's credentials.  An empty string is equivalent to an absent
+   authorization identity.
+
+   A non-empty authorization identity string indicates that the client
+   wishes to act as the identity represented by the string.  In this
+   case, the form of identity represented by the string, as well as the
+   precise syntax and semantics of the string, is protocol specific.
+
+   While the character encoding schema used to transfer the
+   authorization identity string in the authentication exchange is
+   mechanism specific, mechanisms are expected to be capable of carrying
+   the entire Unicode repertoire (with the exception of the NUL
+   character).
+
+3.5.  Aborting Authentication Exchanges
+
+   A client or server may desire to abort an authentication exchange if
+   it is unwilling or unable to continue (or enter into).
+
+   A client may abort the authentication exchange by sending a message,
+   the particulars of which are protocol specific, to the server,
+   indicating that the exchange is aborted.  The server may be required
+   by the protocol to return a message in response to the client's abort
+   message.
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 10]
+
+RFC 4422                          SASL                         June 2006
+
+
+   Likewise, a server may abort the authentication exchange by sending a
+   message, the particulars of which are protocol specific, to the
+   client, indicating that the exchange is aborted.
+
+3.6.  Authentication Outcome
+
+   At the conclusion of the authentication exchange, the server sends a
+   message, the particulars of which are protocol specific, to the
+   client indicating the outcome of the exchange.
+
+   The outcome is not successful if
+
+      -  the authentication exchange failed for any reason,
+
+      -  the client's credentials could not be verified,
+
+      -  the server cannot associate an identity with the client's
+         credentials,
+
+      -  the client-provided authorization identity string is malformed,
+
+      -  the identity associated with the client's credentials is not
+         authorized to act as the requested authorization identity,
+
+      -  the negotiated security layer (or lack thereof) is not
+         suitable, or
+
+      -  the server is not willing to provide service to the client for
+         any reason.
+
+   The protocol may include an optional additional data field in this
+   outcome message.  This field can only include additional data when
+   the outcome is successful.
+
+   If the outcome is successful and a security layer was negotiated,
+   this layer is then installed.  If the outcome is unsuccessful, or a
+   security layer was not negotiated, any existing security is left in
+   place.
+
+   The outcome message provided by the server can provide a way for the
+   client to distinguish between errors that are best dealt with by re-
+   prompting the user for her credentials, errors that are best dealt
+   with by telling the user to try again later, and errors where the
+   user must contact a system administrator for resolution (see the SYS
+   and AUTH POP Response Codes [RFC3206] specification for an example).
+   This distinction is particularly useful during scheduled server
+   maintenance periods as it reduces support costs.  It is also
+   important that the server can be configured such that the outcome
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 11]
+
+RFC 4422                          SASL                         June 2006
+
+
+   message will not distinguish between a valid user with invalid
+   credentials and an invalid user.
+
+3.7.  Security Layers
+
+   SASL mechanisms may offer a wide range of services in security
+   layers.  Typical services include data integrity and data
+   confidentiality.  SASL mechanisms that do not provide a security
+   layer are treated as negotiating no security layer.
+
+   If use of a security layer is negotiated in the authentication
+   protocol exchange, the layer is installed by the server after
+   indicating the outcome of the authentication exchange and installed
+   by the client upon receipt of the outcome indication.  In both cases,
+   the layer is installed before transfer of further protocol data.  The
+   precise position upon which the layer takes effect in the protocol
+   data stream is protocol specific.
+
+   Once the security layer is in effect in the protocol data stream, it
+   remains in effect until either a subsequently negotiated security
+   layer is installed or the underlying transport connection is closed.
+
+   When in effect, the security layer processes protocol data into
+   buffers of protected data.  If at any time the security layer is
+   unable or unwilling to continue producing buffers protecting protocol
+   data, the underlying transport connection MUST be closed.  If the
+   security layer is not able to decode a received buffer, the
+   underlying connection MUST be closed.  In both cases, the underlying
+   transport connection SHOULD be closed gracefully.
+
+   Each buffer of protected data is transferred over the underlying
+   transport connection as a sequence of octets prepended with a four-
+   octet field in network byte order that represents the length of the
+   buffer.  The length of the protected data buffer MUST be no larger
+   than the maximum size that the other side expects.  Upon the receipt
+   of a length field whose value is greater than the maximum size, the
+   receiver SHOULD close the connection, as this might be a sign of an
+   attack.
+
+   The maximum size that each side expects is fixed by the mechanism,
+   either through negotiation or by its specification.
+
+3.8.  Multiple Authentications
+
+   Unless explicitly permitted in the protocol (as stated in the
+   protocol's technical specification), only one successful SASL
+   authentication exchange may occur in a protocol session.  In this
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 12]
+
+RFC 4422                          SASL                         June 2006
+
+
+   case, once an authentication exchange has successfully completed,
+   further attempts to initiate an authentication exchange fail.
+
+   Where multiple successful SASL authentication exchanges are permitted
+   in the protocol, then in no case may multiple SASL security layers be
+   simultaneously in effect.  If a security layer is in effect and a
+   subsequent SASL negotiation selects a second security layer, then the
+   second security layer replaces the first.  If a security layer is in
+   effect and a subsequent SASL negotiation selects no security layer,
+   the original security layer remains in effect.
+
+   Where multiple successful SASL negotiations are permitted in the
+   protocol, the effect of a failed SASL authentication exchange upon
+   the previously established authentication and authorization state is
+   protocol specific.  The protocol's technical specification should be
+   consulted to determine whether the previous authentication and
+   authorization state remains in force, or changed to an anonymous
+   state, or otherwise was affected.  Regardless of the protocol-
+   specific effect upon previously established authentication and
+   authorization state, the previously negotiated security layer remains
+   in effect.
+
+4.  Protocol Requirements
+
+   In order for a protocol to offer SASL services, its specification
+   MUST supply the following information:
+
+   1) A service name, to be selected from registry of "service" elements
+      for the Generic Security Service Application Program Interface
+      (GSSAPI) host-based service name form, as described in Section 4.1
+      of [RFC2743].  Note that this registry is shared by all GSSAPI and
+      SASL mechanisms.
+
+   2) Detail any mechanism negotiation facility that the protocol
+      provides (see Section 3.2).
+
+      A protocol SHOULD specify a facility through which the client may
+      discover, both before initiation of the SASL exchange and after
+      installing security layers negotiated by the exchange, the names
+      of the SASL mechanisms that the server makes available to the
+      client.  The latter is important to allow the client to detect
+      downgrade attacks.  This facility is typically provided through
+      the protocol's extensions or capabilities discovery facility.
+
+   3) Definition of the messages necessary for authentication exchange,
+      including the following:
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 13]
+
+RFC 4422                          SASL                         June 2006
+
+
+      a) A message to initiate the authentication exchange (see Section
+         3.3).
+
+         This message MUST contain a field for carrying the name of the
+         mechanism selected by the client.
+
+         This message SHOULD contain an optional field for carrying an
+         initial response.  If the message is defined with this field,
+         the specification MUST describe how messages with an empty
+         initial response are distinguished from messages with no
+         initial response.  This field MUST be capable of carrying
+         arbitrary sequences of octets (including zero-length sequences
+         and sequences containing zero-valued octets).
+
+      b) Messages to transfer server challenges and client responses
+         (see Section 3.4).
+
+         Each of these messages MUST be capable of carrying arbitrary
+         sequences of octets (including zero-length sequences and
+         sequences containing zero-valued octets).
+
+      c) A message to indicate the outcome of the authentication
+         exchange (see Section 3.6).
+
+         This message SHOULD contain an optional field for carrying
+         additional data with a successful outcome.  If the message is
+         defined with this field, the specification MUST describe how
+         messages with an empty additional data are distinguished from
+         messages with no additional data.  This field MUST be capable
+         of carrying arbitrary sequences of octets (including zero-
+         length sequences and sequences containing zero-valued octets).
+
+   4) Prescribe the syntax and semantics of non-empty authorization
+      identity strings (see Section 3.4.1).
+
+      In order to avoid interoperability problems due to differing
+      normalizations, the protocol specification MUST detail precisely
+      how and where (client or server) non-empty authorization identity
+      strings are prepared, including all normalizations, for comparison
+      and other applicable functions to ensure proper function.
+
+      Specifications are encouraged to prescribe use of existing
+      authorization identity forms as well as existing string
+      representations, such as simple user names [RFC4013].
+
+      Where the specification does not precisely prescribe how
+      identities in SASL relate to identities used elsewhere in the
+      protocol, for instance, in access control policy statements, it
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 14]
+
+RFC 4422                          SASL                         June 2006
+
+
+      may be appropriate for the protocol to provide a facility by which
+      the client can discover information (such as the representation of
+      the identity used in making access control decisions) about
+      established identities for these uses.
+
+   5) Detail any facility the protocol provides that allows the client
+      and/or server to abort authentication exchange (see Section 3.5).
+
+      Protocols that support multiple authentications typically allow a
+      client to abort an ongoing authentication exchange by initiating a
+      new authentication exchange.  Protocols that do not support
+      multiple authentications may require the client to close the
+      connection and start over to abort an ongoing authentication
+      exchange.
+
+      Protocols typically allow the server to abort ongoing
+      authentication exchanges by returning a non-successful outcome
+      message.
+
+   6) Identify precisely where newly negotiated security layers start to
+      take effect, in both directions (see Section 3.7).
+
+      Typically, specifications require security layers to start taking
+      effect on the first octet following the outcome message in data
+      being sent by the server and on the first octet sent after receipt
+      of the outcome message in data being sent by the client.
+
+   7) If the protocol supports other layered security services, such as
+      Transport Layer Security (TLS) [RFC4346], the specification MUST
+      prescribe the order in which security layers are applied to
+      protocol data.
+
+      For instance, where a protocol supports both TLS and SASL security
+      layers, the specification could prescribe any of the following:
+
+      a) SASL security layer is always applied first to data being sent
+         and, hence, applied last to received data,
+
+      b) SASL security layer is always applied last to data being sent
+         and, hence, applied first to received data,
+
+      c) Layers are applied in the order in which they were installed,
+
+      d) Layers are applied in the reverse order in which they were
+         installed, or
+
+      e) Both TLS and SASL security layers cannot be installed.
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 15]
+
+RFC 4422                          SASL                         June 2006
+
+
+   8) Indicate whether the protocol supports multiple authentications
+      (see Section 3.8).  If so, the protocol MUST detail the effect a
+      failed SASL authentication exchange will have upon a previously
+      established authentication and authorization state.
+
+   Protocol specifications SHOULD avoid stating implementation
+   requirements that would hinder replacement of applicable mechanisms.
+   In general, protocol specifications SHOULD be mechanism neutral.
+   There are a number of reasonable exceptions to this recommendation,
+   including
+
+      -  detailing how credentials (which are mechanism specific) are
+         managed in the protocol,
+
+      -  detailing how authentication identities (which are mechanism
+         specific) and authorization identities (which are protocol
+         specific) relate to each other, and
+
+      -  detailing which mechanisms are applicable to the protocol.
+
+5.  Mechanism Requirements
+
+   SASL mechanism specifications MUST supply the following information:
+
+   1) The name of the mechanism (see Section 3.1).  This name MUST be
+      registered as discussed in Section 7.1.
+
+   2) A definition of the server-challenges and client-responses of the
+      authentication exchange, as well as the following:
+
+      a) An indication of whether the mechanism is client-first,
+         variable, or server-first.  If a SASL mechanism is defined as
+         client-first and the client does not send an initial response
+         in the authentication request, then the first server challenge
+         MUST be empty (the EXTERNAL mechanism is an example of this
+         case).  If a SASL mechanism is defined as variable, then the
+         specification needs to state how the server behaves when the
+         initial client response in the authentication request is
+         omitted (the DIGEST-MD5 mechanism [DIGEST-MD5] is an example of
+         this case).  If a SASL mechanism is defined as server-first,
+         then the client MUST NOT send an initial client response in the
+         authentication request (the CRAM-MD5 mechanism [CRAM-MD5] is an
+         example of this case).
+
+      b) An indication of whether the server is expected to provide
+         additional data when indicating a successful outcome.  If so,
+         if the server sends the additional data as a challenge, the
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 16]
+
+RFC 4422                          SASL                         June 2006
+
+
+         specification MUST indicate that the response to this challenge
+         is an empty response.
+
+      SASL mechanisms SHOULD be designed to minimize the number of
+      challenges and responses necessary to complete the exchange.
+
+   3) An indication of whether the mechanism is capable of transferring
+      authorization identity strings (see Section 3.4.1).  While some
+      legacy mechanisms are incapable of transmitting an authorization
+      identity (which means that for these mechanisms, the authorization
+      identity is always the empty string), newly defined mechanisms
+      SHOULD be capable of transferring authorization identity strings.
+      The mechanism SHOULD NOT be capable of transferring both no
+      authorization identity string and an empty authorization identity.
+
+      Mechanisms that are capable of transferring an authorization
+      identity string MUST be capable of transferring arbitrary non-
+      empty sequences of Unicode characters, excluding those that
+      contain the NUL (U+0000) character.  Mechanisms SHOULD use the
+      UTF-8 [RFC3629] transformation format.  The specification MUST
+      detail how any Unicode code points special to the mechanism that
+      might appear in the authorization identity string are escaped to
+      avoid ambiguity during decoding of the authorization identity
+      string.  Typically, mechanisms that have special characters
+      require these special characters to be escaped or encoded in the
+      character string (after encoding it in a particular Unicode
+      transformation format) using a data encoding scheme such as Base64
+      [RFC3548].
+
+   4) The specification MUST detail whether the mechanism offers a
+      security layer.  If the mechanism does, the specification MUST
+      detail the security and other services offered in the layer as
+      well as how these services are to be implemented.
+
+   5) If the underlying cryptographic technology used by a mechanism
+      supports data integrity, then the mechanism specification MUST
+      integrity protect the transmission of an authorization identity
+      and the negotiation of the security layer.
+
+   SASL mechanisms SHOULD be protocol neutral.
+
+   SASL mechanisms SHOULD reuse existing credential and identity forms,
+   as well as associated syntaxes and semantics.
+
+   SASL mechanisms SHOULD use the UTF-8 transformation format [RFC3629]
+   for encoding Unicode [Unicode] code points for transfer.
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 17]
+
+RFC 4422                          SASL                         June 2006
+
+
+   In order to avoid interoperability problems due to differing
+   normalizations, when a mechanism calls for character data (other than
+   the authorization identity string) to be used as input to a
+   cryptographic and/or comparison function, the specification MUST
+   detail precisely how and where (client or server) the character data
+   is to be prepared, including all normalizations, for input into the
+   function to ensure proper operation.
+
+   For simple user names and/or passwords in authentication credentials,
+   SASLprep [RFC4013] (a profile of the StringPrep [RFC3454] preparation
+   algorithm), SHOULD be specified as the preparation algorithm.
+
+   The mechanism SHOULD NOT use the authorization identity string in
+   generation of any long-term cryptographic keys or hashes as there is
+   no requirement that the authorization identity string be canonical.
+   Long-term, here, means a term longer than the duration of the
+   authentication exchange in which they were generated.  That is, as
+   different clients (of the same or different protocol) may provide
+   different authorization identity strings that are semantically
+   equivalent, use of authorization identity strings in generation of
+   cryptographic keys and hashes will likely lead to interoperability
+   and other problems.
+
+6.  Security Considerations
+
+   Security issues are discussed throughout this memo.
+
+   Many existing SASL mechanisms do not provide adequate protection
+   against passive attacks, let alone active attacks, in the
+   authentication exchange.  Many existing SASL mechanisms do not offer
+   security layers.  It is hoped that future SASL mechanisms will
+   provide strong protection against passive and active attacks in the
+   authentication exchange, as well as security layers with strong basic
+   data security features (e.g., data integrity and data
+   confidentiality) services.  It is also hoped that future mechanisms
+   will provide more advanced data security services like re-keying (see
+   Section 6.3).
+
+   Regardless, the SASL framework is susceptible to downgrade attacks.
+   Section 6.1.2 offers a variety of approaches for preventing or
+   detecting these attacks.  In some cases, it is appropriate to use
+   data integrity protective services external to SASL (e.g., TLS) to
+   protect against downgrade attacks in SASL.  Use of external
+   protective security services is also important when the mechanisms
+   available do not themselves offer adequate integrity and/or
+   confidentiality protection of the authentication exchange and/or
+   protocol data.
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 18]
+
+RFC 4422                          SASL                         June 2006
+
+
+6.1.  Active Attacks
+
+6.1.1.  Hijack Attacks
+
+   When the client selects a SASL security layer with at least integrity
+   protection, this protection serves as a counter-measure against an
+   active attacker hijacking the connection and modifying protocol data
+   sent after establishment of the security layer.  Implementations
+   SHOULD close the connection when the security services in a SASL
+   security layer report protocol data report lack of data integrity.
+
+6.1.2.  Downgrade Attacks
+
+   It is important that any security-sensitive protocol negotiations be
+   performed after installation of a security layer with data integrity
+   protection.  Protocols should be designed such that negotiations
+   performed prior to this installation should be revalidated after
+   installation is complete.  Negotiation of the SASL mechanism is
+   security sensitive.
+
+   When a client negotiates the authentication mechanism with the server
+   and/or other security features, it is possible for an active attacker
+   to cause a party to use the least secure security services available.
+   For instance, an attacker can modify the server-advertised mechanism
+   list or can modify the client-advertised security feature list within
+   a mechanism response.  To protect against this sort of attack,
+   implementations SHOULD NOT advertise mechanisms and/or features that
+   cannot meet their minimum security requirements, SHOULD NOT enter
+   into or continue authentication exchanges that cannot meet their
+   minimum security requirements, and SHOULD verify that completed
+   authentication exchanges result in security services that meet their
+   minimum security requirements.  Note that each endpoint needs to
+   independently verify that its security requirements are met.
+
+   In order to detect downgrade attacks to the least (or less) secure
+   mechanism supported, the client can discover the SASL mechanisms that
+   the server makes available both before the SASL authentication
+   exchange and after the negotiated SASL security layer (with at least
+   data integrity protection) has been installed through the protocol's
+   mechanism discovery facility.  If the client finds that the
+   integrity-protected list (the list obtained after the security layer
+   was installed) contains a stronger mechanism than those in the
+   previously obtained list, the client should assume that the
+   previously obtained list was modified by an attacker and SHOULD close
+   the underlying transport connection.
+
+   The client's initiation of the SASL exchange, including the selection
+   of a SASL mechanism, is done in the clear and may be modified by an
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 19]
+
+RFC 4422                          SASL                         June 2006
+
+
+   active attacker.  It is important for any new SASL mechanisms to be
+   designed such that an active attacker cannot obtain an authentication
+   with weaker security properties by modifying the SASL mechanism name
+   and/or the challenges and responses.
+
+   Multi-level negotiation of security features is prone to downgrade
+   attack.  Protocol designers should avoid offering higher-level
+   negotiation of security features in protocols (e.g., above SASL
+   mechanism negotiation) and mechanism designers should avoid lower-
+   level negotiation of security features in mechanisms (e.g., below
+   SASL mechanism negotiation).
+
+6.1.3.  Replay Attacks
+
+   Some mechanisms may be subject to replay attacks unless protected by
+   external data security services (e.g., TLS).
+
+6.1.4.  Truncation Attacks
+
+   Most existing SASL security layers do not themselves offer protection
+   against truncation attack.  In a truncation attack, the active
+   attacker causes the protocol session to be closed, causing a
+   truncation of the possibly integrity-protected data stream that leads
+   to behavior of one or both the protocol peers that inappropriately
+   benefits the attacker.  Truncation attacks are fairly easy to defend
+   against in connection-oriented application-level protocols.  A
+   protocol can defend against these attacks by ensuring that each
+   information exchange has a clear final result and that each protocol
+   session has a graceful closure mechanism, and that these are
+   integrity protected.
+
+6.1.5.  Other Active Attacks
+
+   When use of a security layer is negotiated by the authentication
+   protocol exchange, the receiver SHOULD handle gracefully any
+   protected data buffer larger than the defined/negotiated maximal
+   size.  In particular, it MUST NOT blindly allocate the amount of
+   memory specified in the buffer size field, as this might cause the
+   "out of memory" condition.  If the receiver detects a large block, it
+   SHOULD close the connection.
+
+6.2.  Passive Attacks
+
+   Many mechanisms are subject to various passive attacks, including
+   simple eavesdropping of unprotected credential information as well as
+   online and offline dictionary attacks of protected credential
+   information.
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 20]
+
+RFC 4422                          SASL                         June 2006
+
+
+6.3.  Re-keying
+
+   The secure or administratively permitted lifetimes of SASL
+   mechanisms' security layers are finite.  Cryptographic keys weaken as
+   they are used and as time passes; the more time and/or cipher-text
+   that a cryptanalyst has after the first use of the a key, the easier
+   it is for the cryptanalyst to mount attacks on the key.
+
+   Administrative limits on a security layer's lifetime may take the
+   form of time limits expressed in X.509 certificates, in Kerberos V
+   tickets, or in directories, and are often desired.  In practice, one
+   likely effect of administrative lifetime limits is that applications
+   may find that security layers stop working in the middle of
+   application protocol operation, such as, perhaps, during large data
+   transfers.  As the result of this, the connection will be closed (see
+   Section 3.7), which will result in an unpleasant user experience.
+
+   Re-keying (key renegotiation process) is a way of addressing the
+   weakening of cryptographic keys.  The SASL framework does not itself
+   provide for re-keying; SASL mechanisms may.  Designers of future SASL
+   mechanisms should consider providing re-keying services.
+
+   Implementations that wish to re-key SASL security layers where the
+   mechanism does not provide for re-keying SHOULD reauthenticate the
+   same IDs and replace the expired or soon-to-expire security layers.
+   This approach requires support for reauthentication in the
+   application protocols (see Section 3.8).
+
+6.4.  Other Considerations
+
+   Protocol designers and implementors should understand the security
+   considerations of mechanisms so they may select mechanisms that are
+   applicable to their needs.
+
+   Distributed server implementations need to be careful in how they
+   trust other parties.  In particular, authentication secrets should
+   only be disclosed to other parties that are trusted to manage and use
+   those secrets in a manner acceptable to the disclosing party.
+   Applications using SASL assume that SASL security layers providing
+   data confidentiality are secure even when an attacker chooses the
+   text to be protected by the security layer.  Similarly, applications
+   assume that the SASL security layer is secure even if the attacker
+   can manipulate the cipher-text output of the security layer.  New
+   SASL mechanisms are expected to meet these assumptions.
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 21]
+
+RFC 4422                          SASL                         June 2006
+
+
+   Unicode security considerations [UTR36] apply to authorization
+   identity strings, as well as UTF-8 [RFC3629] security considerations
+   where UTF-8 is used.  SASLprep [RFC4013] and StringPrep [RFC3454]
+   security considerations also apply where used.
+
+7.  IANA Considerations
+
+7.1.  SASL Mechanism Registry
+
+   The SASL mechanism registry is maintained by IANA.  The registry is
+   currently available at <http://www.iana.org/assignments/sasl-
+   mechanisms>.
+
+   The purpose of this registry is not only to ensure uniqueness of
+   values used to name SASL mechanisms, but also to provide a definitive
+   reference to technical specifications detailing each SASL mechanism
+   available for use on the Internet.
+
+   There is no naming convention for SASL mechanisms; any name that
+   conforms to the syntax of a SASL mechanism name can be registered.
+
+   The procedure detailed in Section 7.1.1 is to be used for
+   registration of a value naming a specific individual mechanism.
+
+   The procedure detailed in Section 7.1.2 is to be used for
+   registration of a value naming a family of related mechanisms.
+
+   Comments may be included in the registry as discussed in Section
+   7.1.3 and may be changed as discussed in Section 7.1.4.
+
+   The SASL mechanism registry has been updated to reflect that this
+   document provides the definitive technical specification for SASL and
+   that this section provides the registration procedures for this
+   registry.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 22]
+
+RFC 4422                          SASL                         June 2006
+
+
+7.1.1.  Mechanism Name Registration Procedure
+
+   IANA will register new SASL mechanism names on a First Come First
+   Served basis, as defined in BCP 26 [RFC2434].  IANA has the right to
+   reject obviously bogus registration requests, but will perform no
+   review of claims made in the registration form.
+
+   Registration of a SASL mechanism is requested by filling in the
+   following template:
+
+      Subject: Registration of SASL mechanism X
+
+      SASL mechanism name (or prefix for the family):
+
+      Security considerations:
+
+      Published specification (recommended):
+
+      Person & email address to contact for further information:
+
+      Intended usage: (One of COMMON, LIMITED USE, or OBSOLETE)
+
+      Owner/Change controller:
+
+      Note: (Any other information that the author deems relevant may be
+      added here.)
+
+   and sending it via electronic mail to IANA at <iana@iana.org>.
+
+   While this registration procedure does not require expert review,
+   authors of SASL mechanisms are encouraged to seek community review
+   and comment whenever that is feasible.  Authors may seek community
+   review by posting a specification of their proposed mechanism as an
+   Internet-Draft.  SASL mechanisms intended for widespread use should
+   be standardized through the normal IETF process, when appropriate.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 23]
+
+RFC 4422                          SASL                         June 2006
+
+
+7.1.2.  Family Name Registration Procedure
+
+   As noted above, there is no general naming convention for SASL
+   mechanisms.  However, specifications may reserve a portion of the
+   SASL mechanism namespace for a set of related SASL mechanisms, a
+   "family" of SASL mechanisms.  Each family of SASL mechanisms is
+   identified by a unique prefix, such as X-.  Registration of new SASL
+   mechanism family names requires expert review as defined in BCP 26
+   [RFC2434].
+
+   Registration of a SASL family name is requested by filling in the
+   following template:
+
+      Subject: Registration of SASL mechanism family X
+
+      SASL family name (or prefix for the family):
+
+      Security considerations:
+
+      Published specification (recommended):
+
+      Person & email address to contact for further information:
+
+      Intended usage: (One of COMMON, LIMITED USE, or OBSOLETE)
+
+      Owner/Change controller:
+
+      Note: (Any other information that the author deems relevant may be
+      added here.)
+
+   and sending it via electronic mail to the IETF SASL mailing list at
+   <ietf-sasl@imc.org> and carbon copying IANA at <iana@iana.org>.
+   After allowing two weeks for community input on the IETF SASL mailing
+   list, the expert will determine the appropriateness of the
+   registration request and either approve or disapprove the request
+   with notice to the requestor, the mailing list, and IANA.
+
+   The review should focus on the appropriateness of the requested
+   family name for the proposed use and the appropriateness of the
+   proposed naming and registration plan for existing and future
+   mechanism names in the family.  The scope of this request review may
+   entail consideration of relevant aspects of any provided technical
+   specification, such as their IANA Considerations section.  However,
+   this review is narrowly focused on the appropriateness of the
+   requested registration and not on the overall soundness of any
+   provided technical specification.
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 24]
+
+RFC 4422                          SASL                         June 2006
+
+
+   Authors are encouraged to pursue community review by posting the
+   technical specification as an Internet-Draft and soliciting comment
+   by posting to appropriate IETF mailing lists.
+
+7.1.3.  Comments on SASL Mechanism Registrations
+
+   Comments on a registered SASL mechanism/family should first be sent
+   to the "owner" of the mechanism/family and/or to the <ietf-
+   sasl@imc.org> mailing list.
+
+   Submitters of comments may, after a reasonable attempt to contact the
+   owner, request IANA to attach their comment to the SASL mechanism
+   registration itself by sending mail to <iana@iana.org>.  At IANA's
+   sole discretion, IANA may attach the comment to the SASL mechanism's
+   registration.
+
+7.1.4.  Change Control
+
+   Once a SASL mechanism registration has been published by IANA, the
+   author may request a change to its definition.  The change request
+   follows the same procedure as the registration request.
+
+   The owner of a SASL mechanism may pass responsibility for the SASL
+   mechanism to another person or agency by informing IANA; this can be
+   done without discussion or review.
+
+   The IESG may reassign responsibility for a SASL mechanism.  The most
+   common case of this will be to enable changes to be made to
+   mechanisms where the author of the registration has died, has moved
+   out of contact, or is otherwise unable to make changes that are
+   important to the community.
+
+   SASL mechanism registrations may not be deleted; mechanisms that are
+   no longer believed appropriate for use can be declared OBSOLETE by a
+   change to their "intended usage" field; such SASL mechanisms will be
+   clearly marked in the lists published by IANA.
+
+   The IESG is considered to be the owner of all SASL mechanisms that
+   are on the IETF standards track.
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 25]
+
+RFC 4422                          SASL                         June 2006
+
+
+7.2.  Registration Changes
+
+   The IANA has updated the SASL mechanisms registry as follows:
+
+   1) Changed the "Intended usage" of the KERBEROS_V4 and SKEY mechanism
+      registrations to OBSOLETE.
+
+   2) Changed the "Published specification" of the EXTERNAL mechanism to
+      this document as indicated below:
+
+      Subject: Updated Registration of SASL mechanism EXTERNAL
+      Family of SASL mechanisms: NO
+      SASL mechanism name: EXTERNAL
+      Security considerations: See A.3 of RFC 4422
+      Published specification (optional, recommended): RFC 4422
+      Person & email address to contact for further information:
+          Alexey Melnikov <Alexey.Melnikov@isode.com>
+      Intended usage: COMMON
+      Owner/Change controller: IESG <iesg@ietf.org>
+      Note: Updates existing entry for EXTERNAL
+
+8.  References
+
+8.1.  Normative References
+
+   [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
+                 Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC2244]     Newman, C. and J. G. Myers, "ACAP -- Application
+                 Configuration Access Protocol", RFC 2244, November
+                 1997.
+
+   [RFC2434]     Narten, T. and H. Alvestrand, "Guidelines for Writing
+                 an IANA Considerations Section in RFCs", BCP 26, RFC
+                 2434, October 1998.
+
+   [RFC2743]     Linn, J., "Generic Security Service Application Program
+                 Interface Version 2, Update 1", RFC 2743, January 2000.
+
+   [RFC3454]     Hoffman, P. and M. Blanchet, "Preparation of
+                 Internationalized Strings ("stringprep")", RFC 3454,
+                 December 2002.
+
+   [RFC3629]     Yergeau, F., "UTF-8, a transformation format of ISO
+                 10646", STD 63, RFC 3629, November 2003.
+
+   [RFC4013]     Zeilenga, K., "SASLprep: Stringprep Profile for User
+                 Names and Passwords", RFC 4013, February 2005.
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 26]
+
+RFC 4422                          SASL                         June 2006
+
+
+   [RFC4234]     Crocker, D. and P. Overell, "Augmented BNF for Syntax
+                 Specifications: ABNF", RFC 4234, October 2005.
+
+   [ASCII]       Coded Character Set--7-bit American Standard Code for
+                 Information Interchange, ANSI X3.4-1986.
+
+   [Unicode]     The Unicode Consortium, "The Unicode Standard, Version
+                 3.2.0" is defined by "The Unicode Standard, Version
+                 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
+                 61633-5), as amended by the "Unicode Standard Annex
+                 #27: Unicode 3.1"
+                 (http://www.unicode.org/reports/tr27/) and by the
+                 "Unicode Standard Annex #28: Unicode 3.2"
+                 (http://www.unicode.org/reports/tr28/).
+
+   [CharModel]   Whistler, K. and M. Davis, "Unicode Technical Report
+                 #17, Character Encoding Model", UTR17,
+                 <http://www.unicode.org/unicode/reports/tr17/>, August
+                 2000.
+
+   [Glossary]    The Unicode Consortium, "Unicode Glossary",
+                 <http://www.unicode.org/glossary/>.
+
+8.2.  Informative References
+
+   [RFC3206]     Gellens, R., "The SYS and AUTH POP Response Codes", RFC
+                 3206, February 2002.
+
+   [RFC3548]     Josefsson, S., "The Base16, Base32, and Base64 Data
+                 Encodings", RFC 3548, July 2003.
+
+   [RFC4301]     Kent, S. and K. Seo, "Security Architecture for the
+                 Internet Protocol", RFC 4301, December 2005.
+
+   [RFC4346]     Dierks, T. and E. Rescorla, "The Transport Layer
+                 Security (TLS) Protocol Version 1.1", RFC 4346, April
+                 2006.
+
+   [SASL-GSSAPI] Melnikov, A. (Editor), "The Kerberos V5 ("GSSAPI") SASL
+                 Mechanism", Work in Progress, May 2006.
+
+   [UTR36]       Davis, M., "(Draft) Unicode Technical Report #36,
+                 Character Encoding Model", UTR17,
+                 <http://www.unicode.org/unicode/reports/tr36/>,
+                 February 2005.
+
+   [CRAM-MD5]    Nerenberg, L., "The CRAM-MD5 SASL Mechanism", Work in
+                 Progress.
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 27]
+
+RFC 4422                          SASL                         June 2006
+
+
+   [DIGEST-MD5]  Leach, P., C. Newman, and A. Melnikov, "Using Digest
+                 Authentication as a SASL Mechanism", Work in Progress,
+                 March 2006.
+
+9.  Acknowledgements
+
+   This document is a revision of RFC 2222 written by John Myers.
+
+   This revision is a product of the IETF Simple Authentication and
+   Security Layer (SASL) Working Group.
+
+   The following individuals contributed significantly to this revision:
+   Abhijit Menon-Sen, Hallvard Furuseth, Jeffrey Hutzelman, John Myers,
+   Luke Howard, Magnus Nystrom, Nicolas Williams, Peter Saint-Andre, RL
+   'Bob' Morgan, Rob Siemborski, Sam Hartman, Simon Josefsson, Tim
+   Alsop, and Tony Hansen.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 28]
+
+RFC 4422                          SASL                         June 2006
+
+
+Appendix A.  The SASL EXTERNAL Mechanism
+
+   This appendix is normative.
+
+   The EXTERNAL mechanism allows a client to request the server to use
+   credentials established by means external to the mechanism to
+   authenticate the client.  The external means may be, for instance, IP
+   Security [RFC4301] or TLS [RFC4346] services.  In absence of some a
+   priori agreement between the client and the server, the client cannot
+   make any assumption as to what external means the server has used to
+   obtain the client's credentials, nor make an assumption as to the
+   form of credentials.  For example, the client cannot assume that the
+   server will use the credentials the client has established via TLS.
+
+A.1.  EXTERNAL Technical Specification
+
+   The name of this mechanism is "EXTERNAL".
+
+   The mechanism does not provide a security layer.
+
+   The mechanism is capable of transferring an authorization identity
+   string.  If empty, the client is requesting to act as the identity
+   the server has associated with the client's credentials.  If non-
+   empty, the client is requesting to act as the identity represented by
+   the string.
+
+   The client is expected to send data first in the authentication
+   exchange.  Where the client does not provide an initial response data
+   in its request to initiate the authentication exchange, the server is
+   to respond to the request with an empty initial challenge and then
+   the client is to provide its initial response.
+
+   The client sends the initial response containing the UTF-8 [RFC3629]
+   encoding of the requested authorization identity string.  This
+   response is non-empty when the client is requesting to act as the
+   identity represented by the (non-empty) string.  This response is
+   empty when the client is requesting to act as the identity the server
+   associated with its authentication credentials.
+
+   The syntax of the initial response is specified as a value of the
+   <extern-initial-resp> production detailed below using the Augmented
+   Backus-Naur Form (ABNF) [RFC4234] notation.
+
+      external-initial-resp = authz-id-string
+      authz-id-string       = *( UTF8-char-no-nul )
+      UTF8-char-no-nul      = UTF8-1-no-nul / UTF8-2 / UTF8-3 / UTF8-4
+      UTF8-1-no-nul         = %x01-7F
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 29]
+
+RFC 4422                          SASL                         June 2006
+
+
+   where the <UTF8-2>, <UTF8-3>, and <UTF8-4> productions are as defined
+   in [RFC3629].
+
+   There are no additional challenges and responses.
+
+   Hence, the server is to return the outcome of the authentication
+   exchange.
+
+   The exchange fails if
+
+   -  the client has not established its credentials via external means,
+
+   -  the client's credentials are inadequate,
+
+   -  the client provided an empty authorization identity string and the
+      server is unwilling or unable to associate an authorization
+      identity with the client's credentials,
+
+   -  the client provided a non-empty authorization identity string that
+      is invalid per the syntax requirements of the applicable
+      application protocol specification,
+
+   -  the client provided a non-empty authorization identity string
+      representing an identity that the client is not allowed to act as,
+      or
+
+   -  the server is unwilling or unable to provide service to the client
+      for any other reason.
+
+   Otherwise the exchange is successful.  When indicating a successful
+   outcome, additional data is not provided.
+
+A.2.  SASL EXTERNAL Examples
+
+   This section provides examples of EXTERNAL authentication exchanges.
+   The examples are intended to help the readers understand the above
+   text.  The examples are not definitive.  The Application
+   Configuration Access Protocol (ACAP) [RFC2244] is used in the
+   examples.
+
+   The first example shows use of EXTERNAL with an empty authorization
+   identity.  In this example, the initial response is not sent in the
+   client's request to initiate the authentication exchange.
+
+      S: * ACAP (SASL "DIGEST-MD5")
+      C: a001 STARTTLS
+      S: a001 OK "Begin TLS negotiation now"
+      <TLS negotiation, further commands are under TLS layer>
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 30]
+
+RFC 4422                          SASL                         June 2006
+
+
+      S: * ACAP (SASL "DIGEST-MD5" "EXTERNAL")
+      C: a002 AUTHENTICATE "EXTERNAL"
+      S: + ""
+      C: + ""
+      S: a002 OK "Authenticated"
+
+   The second example shows use of EXTERNAL with an authorization
+   identity of "fred@example.com".  In this example, the initial
+   response is sent with the client's request to initiate the
+   authentication exchange.  This saves a round-trip.
+
+      S: * ACAP (SASL "DIGEST-MD5")
+      C: a001 STARTTLS
+      S: a001 OK "Begin TLS negotiation now"
+      <TLS negotiation, further commands are under TLS layer>
+      S: * ACAP (SASL "DIGEST-MD5" "EXTERNAL")
+      C: a002 AUTHENTICATE "EXTERNAL" {16+}
+      C: fred@example.com
+      S: a002 NO "Cannot assume requested authorization identity"
+
+A.3.  Security Considerations
+
+   The EXTERNAL mechanism provides no security protection; it is
+   vulnerable to spoofing by either client or server, active attack, and
+   eavesdropping.  It should only be used when adequate security
+   services have been established.
+
+Appendix B.  Changes since RFC 2222
+
+   This appendix is non-normative.
+
+   The material in RFC 2222 was significantly rewritten in the
+   production of this document.
+
+   RFC 2222, by not stating that the authorization identity string was a
+   string of Unicode characters, let alone character data, implied that
+   the authorization identity string was a string of octets.
+
+   -  The authorization identity string is now defined as a string of
+      Unicode characters.  The NUL (U+0000) character is prohibited.
+      While protocol specifications are responsible for defining the
+      authorization identity form, as well as the Unicode string syntax
+      and related semantics, mechanism specifications are responsible
+      for defining how the Unicode string is carried in the
+      authentication exchange.
+
+   -  Deleted "If so, when the client does not send data first, the
+      initial challenge MUST be specified as being an empty challenge."
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 31]
+
+RFC 4422                          SASL                         June 2006
+
+
+   The following technical change was made to the EXTERNAL mechanism:
+
+      - The authorization identity string is to be UTF-8 encoded.
+
+      Note that protocol and mechanism specification requirements have
+      been significantly tightened.  Existing protocol and mechanism
+      specifications will need to be updated to meet these requirements.
+
+Editors' Addresses
+
+   Alexey Melnikov
+   Isode Limited
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex,
+   TW12 2BX, United Kingdom
+
+   EMail: Alexey.Melnikov@isode.com
+   URI:   http://www.melnikov.ca/
+
+
+   Kurt D. Zeilenga
+   OpenLDAP Foundation
+
+   EMail: Kurt@OpenLDAP.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 32]
+
+RFC 4422                          SASL                         June 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Melnikov & Zeilenga         Standards Track                    [Page 33]
+
diff --git a/imap/docs/rfc/rfc4466.txt b/imap/docs/rfc/rfc4466.txt
new file mode 100644
index 00000000..dfde1685
--- /dev/null
+++ b/imap/docs/rfc/rfc4466.txt
@@ -0,0 +1,955 @@
+
+
+
+
+
+
+Network Working Group                                        A. Melnikov
+Request for Comments: 4466                                    Isode Ltd.
+Updates: 2088, 2342, 3501, 3502, 3516                           C. Daboo
+Category: Standards Track                                     April 2006
+
+
+                   Collected Extensions to IMAP4 ABNF
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   Over the years, many documents from IMAPEXT and LEMONADE working
+   groups, as well as many individual documents, have added syntactic
+   extensions to many base IMAP commands described in RFC 3501.  For
+   ease of reference, this document collects most of such ABNF changes
+   in one place.
+
+   This document also suggests a set of standard patterns for adding
+   options and extensions to several existing IMAP commands defined in
+   RFC 3501.  The patterns provide for compatibility between existing
+   and future extensions.
+
+   This document updates ABNF in RFCs 2088, 2342, 3501, 3502, and 3516.
+   It also includes part of the errata to RFC 3501.  This document
+   doesn't specify any semantic changes to the listed RFCs.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 1]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+Table of Contents
+
+   1. Introduction ....................................................2
+      1.1. Purpose of This Document ...................................2
+      1.2. Conventions Used in This Document ..........................3
+   2. IMAP ABNF Extensions ............................................3
+      2.1. Optional Parameters with the SELECT/EXAMINE Commands .......3
+      2.2. Extended CREATE Command ....................................4
+      2.3. Extended RENAME Command ....................................5
+      2.4. Extensions to FETCH and UID FETCH Commands .................6
+      2.5. Extensions to STORE and UID STORE Commands .................6
+      2.6. Extensions to SEARCH Command ...............................7
+           2.6.1. Extended SEARCH Command .............................7
+           2.6.2. ESEARCH untagged response ...........................8
+      2.7. Extensions to APPEND Command ...............................8
+   3. Formal Syntax ...................................................9
+   4. Security Considerations ........................................14
+   5. Normative References ...........................................15
+   6. Acknowledgements ...............................................15
+
+1.  Introduction
+
+1.1.  Purpose of This Document
+
+   This document serves several purposes:
+
+      1.  rationalize and generalize ABNF for some existing IMAP
+          extensions;
+      2.  collect the ABNF in one place in order to minimize cross
+          references between documents;
+      3.  define building blocks for future extensions so that they can
+          be used together in a compatible way.
+
+   It is expected that a future revision of this document will be
+   incorporated into a revision of RFC 3501.
+
+   This document updates ABNF in RFCs 2088, 2342, 3501, 3502, and 3516.
+   It also includes part of the errata to RFC 3501.  This document
+   doesn't specify any semantic changes to the listed RFCs.
+
+   The ABNF in section 6 of RFC 2342 got rewritten to conform to the
+   ABNF syntax as defined in RFC 4234 and to reference new non-terminals
+   from RFC 3501.  It was also restructured to allow for better
+   readability.  There were no changes "on the wire".
+
+   Section 2 extends ABNF for SELECT, EXAMINE, CREATE, RENAME, FETCH/UID
+   FETCH, STORE/UID STORE, SEARCH, and APPEND commands in a consistent
+   manner.  Extensions to all the commands but APPEND have the same
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 2]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   structure.  Extensibility for the APPEND command was done slightly
+   differently in order to preserve backward compatibility with existing
+   extensions.
+
+   Section 2 also defines a new ESEARCH response, whose purpose is to
+   define a better version of the SEARCH response defined in RFC 3501.
+
+   Section 3 defines the collected ABNF that replaces pieces of ABNF in
+   the aforementioned RFCs.  The collected ABNF got generalized to allow
+   for easier future extensibility.
+
+1.2.  Conventions Used in This Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.
+
+   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+   in this document are to be interpreted as defined in "Key words for
+   use in RFCs to Indicate Requirement Levels" [KEYWORDS].
+
+2.  IMAP ABNF Extensions
+
+   This section is not normative.  It provides some background on the
+   intended use of different extensions and it gives some guidance about
+   how future extensions should extend the described commands.
+
+2.1.  Optional Parameters with the SELECT/EXAMINE Commands
+
+   This document adds the ability to include one or more parameters with
+   the IMAP SELECT (section 6.3.1 of [IMAP4]) or EXAMINE (section 6.3.2
+   of [IMAP4]) commands, to turn on or off certain standard behaviors,
+   or to add new optional behaviors required for a particular extension.
+
+   There are two possible modes of operation:
+
+   o  A global state change where a single use of the optional parameter
+      will affect the session state from that time on, irrespective of
+      subsequent SELECT/EXAMINE commands.
+
+   o  A per-mailbox state change that will affect the session only for
+      the duration of the new selected state.  A subsequent
+      SELECT/EXAMINE without the optional parameter will cancel its
+      effect for the newly selected mailbox.
+
+   Optional parameters to the SELECT or EXAMINE commands are added as a
+   parenthesized list of attribute/value pairs, and appear after the
+   mailbox name in the standard SELECT or EXAMINE command.  The order of
+   individual parameters is arbitrary.  A parameter value is optional
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 3]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   and may consist of atoms, strings, or lists in a specific order.  If
+   the parameter value is present, it always appears in parentheses (*).
+   Any parameter not defined by extensions that the server supports must
+   be rejected with a BAD response.
+
+      Example:
+
+              C: a SELECT INBOX (ANNOTATE)
+              S: ...
+              S: a OK SELECT complete
+
+      In the above example, a single parameter is used with the SELECT
+      command.
+
+      Example:
+
+              C: a EXAMINE INBOX (ANNOTATE RESPONSES ("UID Responses")
+                 CONDSTORE)
+              S: ...
+              S: a OK EXAMINE complete
+
+      In the above example, three parameters are used with the EXAMINE
+      command.  The second parameter consists of two items: an atom
+      "RESPONSES" followed by a quoted string.
+
+      Example:
+
+              C: a SELECT INBOX (BLURDYBLOOP)
+              S: a BAD Unknown parameter in SELECT command
+
+      In the above example, a parameter not supported by the server is
+      used.  This results in the BAD response from the server.
+
+   (*) - if a parameter has a mandatory value, which can always be
+   represented as a number or a sequence-set, the parameter value does
+   not need the enclosing ().  See ABNF for more details.
+
+2.2.  Extended CREATE Command
+
+   Arguments:  mailbox name
+               OPTIONAL list of CREATE parameters
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - create completed
+               NO - create failure: cannot create mailbox with
+                    that name
+               BAD - argument(s) invalid
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 4]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   This document adds the ability to include one or more parameters with
+   the IMAP CREATE command (see section 6.3.3 of [IMAP4]), to turn on or
+   off certain standard behaviors, or to add new optional behaviors
+   required for a particular extension.  No CREATE parameters are
+   defined in this document.
+
+   Optional parameters to the CREATE command are added as a
+   parenthesized list of attribute/value pairs after the mailbox name.
+   The order of individual parameters is arbitrary.  A parameter value
+   is optional and may consist of atoms, strings, or lists in a specific
+   order.  If the parameter value is present, it always appears in
+   parentheses (*).  Any parameter not defined by extensions that the
+   server supports must be rejected with a BAD response.
+
+   (*) - if a parameter has a mandatory value, which can always be
+   represented as a number or a sequence-set, the parameter value does
+   not need the enclosing ().  See ABNF for more details.
+
+2.3.  Extended RENAME Command
+
+   Arguments:  existing mailbox name
+               new mailbox name
+               OPTIONAL list of RENAME parameters
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - rename completed
+               NO - rename failure: cannot rename mailbox with
+                    that name, cannot rename to mailbox with
+                    that name, etc.
+               BAD - argument(s) invalid
+
+   This document adds the ability to include one or more parameters with
+   the IMAP RENAME command (see section 6.3.5 of [IMAP4]), to turn on or
+   off certain standard behaviors, or to add new optional behaviors
+   required for a particular extension.  No RENAME parameters are
+   defined in this document.
+
+   Optional parameters to the RENAME command are added as a
+   parenthesized list of attribute/value pairs after the new mailbox
+   name.  The order of individual parameters is arbitrary.  A parameter
+   value is optional and may consist of atoms, strings, or lists in a
+   specific order.  If the parameter value is present, it always appears
+   in parentheses (*).  Any parameter not defined by extensions that the
+   server supports must be rejected with a BAD response.
+
+
+
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 5]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   (*) - if a parameter has a mandatory value, which can always be
+   represented as a number or a sequence-set, the parameter value does
+   not need the enclosing ().  See ABNF for more details.
+
+2.4.  Extensions to FETCH and UID FETCH Commands
+
+   Arguments:  sequence set
+               message data item names or macro
+               OPTIONAL fetch modifiers
+
+   Responses:  untagged responses: FETCH
+
+   Result:     OK - fetch completed
+               NO - fetch error: cannot fetch that data
+               BAD - command unknown or arguments invalid
+
+   This document extends the syntax of the FETCH and UID FETCH commands
+   (see section 6.4.5 of [IMAP4]) to include optional FETCH modifiers.
+   No fetch modifiers are defined in this document.
+
+   The order of individual modifiers is arbitrary.  Each modifier is an
+   attribute/value pair.  A modifier value is optional and may consist
+   of atoms and/or strings and/or lists in a specific order.  If the
+   modifier value is present, it always appears in parentheses (*).  Any
+   modifiers not defined by extensions that the server supports must be
+   rejected with a BAD response.
+
+   (*) - if a modifier has a mandatory value, which can always be
+   represented as a number or a sequence-set, the modifier value does
+   not need the enclosing ().  See ABNF for more details.
+
+2.5.  Extensions to STORE and UID STORE Commands
+
+   Arguments:  message set
+               OPTIONAL store modifiers
+               message data item name
+               value for message data item
+
+   Responses:  untagged responses: FETCH
+
+   Result:     OK - store completed
+               NO - store error: cannot store that data
+               BAD - command unknown or arguments invalid
+
+   This document extends the syntax of the STORE and UID STORE commands
+   (see section 6.4.6 of [IMAP4]) to include optional STORE modifiers.
+   No store modifiers are defined in this document.
+
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 6]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   The order of individual modifiers is arbitrary.  Each modifier is an
+   attribute/value pair.  A modifier value is optional and may consist
+   of atoms and/or strings and/or lists in a specific order.  If the
+   modifier value is present, it always appears in parentheses (*).  Any
+   modifiers not defined by extensions that the server supports must be
+   rejected with a BAD response.
+
+   (*) - if a modifier has a mandatory value, which can always be
+   represented as a number or a sequence-set, the modifier value does
+   not need the enclosing ().  See ABNF for more details.
+
+2.6.  Extensions to SEARCH Command
+
+2.6.1.  Extended SEARCH Command
+
+   Arguments:  OPTIONAL result specifier
+               OPTIONAL [CHARSET] specification
+               searching criteria (one or more)
+
+   Responses:  REQUIRED untagged response: SEARCH (*)
+
+   Result:     OK - search completed
+               NO - search error: cannot search that [CHARSET] or
+                    criteria
+               BAD - command unknown or arguments invalid
+
+   This section updates definition of the SEARCH command described in
+   section 6.4.4 of [IMAP4].
+
+   The SEARCH command is extended to allow for result options.  This
+   document does not define any result options.
+
+   The order of individual options is arbitrary.  Individual options may
+   contain parameters enclosed in parentheses (**).  If an option has
+   parameters, they consist of atoms and/or strings and/or lists in a
+   specific order.  Any options not defined by extensions that the
+   server supports must be rejected with a BAD response.
+
+   (*) - An extension to the SEARCH command may require another untagged
+   response, or no untagged response to be returned.  Section 2.6.2
+   defines a new ESEARCH untagged response that replaces the SEARCH
+   untagged response.  Note that for a given extended SEARCH command the
+   SEARCH and ESEARCH responses SHOULD be mutually exclusive, i.e., only
+   one of them should be returned.
+
+   (**) - if an option has a mandatory parameter, which can always be
+   represented as a number or a sequence-set, the option parameter does
+   not need the enclosing ().  See ABNF for more details.
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 7]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+2.6.2.  ESEARCH untagged response
+
+   Contents:   one or more search-return-data pairs
+
+   The ESEARCH response SHOULD be sent as a result of an extended SEARCH
+   or UID SEARCH command specified in section 2.6.1.
+
+   The ESEARCH response starts with an optional search correlator.  If
+   it is missing, then the response was not caused by a particular IMAP
+   command, whereas if it is present, it contains the tag of the command
+   that caused the response to be returned.
+
+   The search correlator is followed by an optional UID indicator.  If
+   this indicator is present, all data in the ESEARCH response refers to
+   UIDs, otherwise all returned data refers to message numbers.
+
+   The rest of the ESEARCH response contains one or more search data
+   pairs.  Each pair starts with unique return item name, followed by a
+   space and the corresponding data.  Search data pairs may be returned
+   in any order.  Unless specified otherwise by an extension, any return
+   item name SHOULD appear only once in an ESEARCH response.
+
+   Example:    S: * ESEARCH UID COUNT 5 ALL 4:19,21,28
+
+   Example:    S: * ESEARCH (TAG "a567") UID COUNT 5 ALL 4:19,21,28
+
+   Example:    S: * ESEARCH COUNT 5 ALL 1:17,21
+
+2.7.  Extensions to APPEND Command
+
+   The IMAP BINARY extension [BINARY] extends the APPEND command to
+   allow a client to append data containing NULs by using the <literal8>
+   syntax.  The ABNF was rewritten to allow for easier extensibility by
+   IMAP extensions.  This document hasn't specified any semantical
+   changes to the [BINARY] extension.
+
+   In addition, the non-terminal "literal8" defined in [BINARY] got
+   extended to allow for non-synchronizing literals if both [BINARY] and
+   [LITERAL+] extensions are supported by the server.
+
+   The IMAP MULTIAPPEND extension [MULTIAPPEND] extends the APPEND
+   command to allow a client to append multiple messages atomically.
+   This document defines a common syntax for the APPEND command that
+   takes into consideration syntactic extensions defined by both
+   [BINARY] and [MULTIAPPEND] extensions.
+
+
+
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 8]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+3.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].
+
+   Non-terminals referenced but not defined below are as defined by
+   [IMAP4].
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of uppercase or lowercase characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+   append          = "APPEND" SP mailbox 1*append-message
+                     ;; only a single append-message may appear
+                     ;; if MULTIAPPEND [MULTIAPPEND] capability
+                     ;; is not present
+
+   append-message  = append-opts SP append-data
+
+   append-ext      = append-ext-name SP append-ext-value
+                     ;; This non-terminal define extensions to
+                     ;; to message metadata.
+
+   append-ext-name = tagged-ext-label
+
+   append-ext-value= tagged-ext-val
+                     ;; This non-terminal shows recommended syntax
+                     ;; for future extensions.
+
+
+   append-data     = literal / literal8 / append-data-ext
+
+   append-data-ext = tagged-ext
+                     ;; This non-terminal shows recommended syntax
+                     ;; for future extensions,
+                     ;; i.e., a mandatory label followed
+                     ;; by parameters.
+
+   append-opts     = [SP flag-list] [SP date-time] *(SP append-ext)
+                     ;; message metadata
+
+   charset         = atom / quoted
+                     ;; Exact syntax is defined in [CHARSET].
+
+   create          = "CREATE" SP mailbox
+                     [create-params]
+                     ;; Use of INBOX gives a NO error.
+
+
+
+Melnikov & Daboo            Standards Track                     [Page 9]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   create-params   = SP "(" create-param *( SP create-param) ")"
+
+   create-param-name = tagged-ext-label
+
+   create-param      = create-param-name [SP create-param-value]
+
+   create-param-value= tagged-ext-val
+                     ;; This non-terminal shows recommended syntax
+                     ;; for future extensions.
+
+
+   esearch-response  = "ESEARCH" [search-correlator] [SP "UID"]
+                        *(SP search-return-data)
+                      ;; Note that SEARCH and ESEARCH responses
+                      ;; SHOULD be mutually exclusive,
+                      ;; i.e., only one of the response types
+                      ;; should be
+                      ;; returned as a result of a command.
+
+
+   examine         = "EXAMINE" SP mailbox [select-params]
+                     ;; modifies the original IMAP EXAMINE command
+                     ;; to accept optional parameters
+
+   fetch           = "FETCH" SP sequence-set SP ("ALL" / "FULL" /
+                     "FAST" / fetch-att /
+                     "(" fetch-att *(SP fetch-att) ")")
+                     [fetch-modifiers]
+                     ;; modifies the original IMAP4 FETCH command to
+                     ;; accept optional modifiers
+
+   fetch-modifiers = SP "(" fetch-modifier *(SP fetch-modifier) ")"
+
+   fetch-modifier  = fetch-modifier-name [ SP fetch-modif-params ]
+
+   fetch-modif-params  = tagged-ext-val
+                     ;; This non-terminal shows recommended syntax
+                     ;; for future extensions.
+
+   fetch-modifier-name = tagged-ext-label
+
+   literal8        = "~{" number ["+"] "}" CRLF *OCTET
+                      ;; A string that might contain NULs.
+                      ;; <number> represents the number of OCTETs
+                      ;; in the response string.
+                      ;; The "+" is only allowed when both LITERAL+ and
+                      ;; BINARY extensions are supported by the server.
+
+
+
+
+Melnikov & Daboo            Standards Track                    [Page 10]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   mailbox-data      =/ Namespace-Response /
+                        esearch-response
+
+   Namespace         = nil / "(" 1*Namespace-Descr ")"
+
+   Namespace-Command = "NAMESPACE"
+
+   Namespace-Descr   = "(" string SP
+                          (DQUOTE QUOTED-CHAR DQUOTE / nil)
+                           *(Namespace-Response-Extension) ")"
+
+   Namespace-Response-Extension = SP string SP
+                     "(" string *(SP string) ")"
+
+   Namespace-Response = "NAMESPACE" SP Namespace
+                        SP Namespace SP Namespace
+         ;; This response is currently only allowed
+         ;; if the IMAP server supports [NAMESPACE].
+         ;; The first Namespace is the Personal Namespace(s)
+         ;; The second Namespace is the Other Users' Namespace(s)
+         ;; The third Namespace is the Shared Namespace(s)
+
+   rename          = "RENAME" SP mailbox SP mailbox
+                     [rename-params]
+                     ;; Use of INBOX as a destination gives
+                     ;; a NO error, unless rename-params
+                     ;; is not empty.
+
+   rename-params     = SP "(" rename-param *( SP rename-param) ")"
+
+   rename-param      = rename-param-name [SP rename-param-value]
+
+   rename-param-name = tagged-ext-label
+
+   rename-param-value= tagged-ext-val
+                     ;; This non-terminal shows recommended syntax
+                     ;; for future extensions.
+
+
+   response-data   = "*" SP response-payload CRLF
+
+   response-payload= resp-cond-state / resp-cond-bye /
+                     mailbox-data / message-data / capability-data
+
+   search          = "SEARCH" [search-return-opts]
+                     SP search-program
+
+   search-correlator  = SP "(" "TAG" SP tag-string ")"
+
+
+
+Melnikov & Daboo            Standards Track                    [Page 11]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   search-program     = ["CHARSET" SP charset SP]
+                        search-key *(SP search-key)
+                        ;; CHARSET argument to SEARCH MUST be
+                        ;; registered with IANA.
+
+   search-return-data = search-modifier-name SP search-return-value
+                        ;; Note that not every SEARCH return option
+                        ;; is required to have the corresponding
+                        ;; ESEARCH return data.
+
+   search-return-opts = SP "RETURN" SP "(" [search-return-opt
+                        *(SP search-return-opt)] ")"
+
+   search-return-opt = search-modifier-name [SP search-mod-params]
+
+   search-return-value = tagged-ext-val
+                        ;; Data for the returned search option.
+                        ;; A single "nz-number"/"number" value
+                        ;; can be returned as an atom (i.e., without
+                        ;; quoting).  A sequence-set can be returned
+                        ;; as an atom as well.
+
+   search-modifier-name = tagged-ext-label
+
+   search-mod-params = tagged-ext-val
+                     ;; This non-terminal shows recommended syntax
+                     ;; for future extensions.
+
+
+   select          = "SELECT" SP mailbox [select-params]
+                     ;; modifies the original IMAP SELECT command to
+                     ;; accept optional parameters
+
+   select-params   = SP "(" select-param *(SP select-param) ")"
+
+   select-param    = select-param-name [SP select-param-value]
+                     ;; a parameter to SELECT may contain one or
+                     ;; more atoms and/or strings and/or lists.
+
+   select-param-name= tagged-ext-label
+
+   select-param-value= tagged-ext-val
+                     ;; This non-terminal shows recommended syntax
+                     ;; for future extensions.
+
+
+   status-att-list = status-att-val *(SP status-att-val)
+                     ;; Redefines status-att-list from RFC 3501.
+
+
+
+Melnikov & Daboo            Standards Track                    [Page 12]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+                     ;; status-att-val is defined in RFC 3501 errata
+
+   status-att-val  = ("MESSAGES" SP number) /
+                     ("RECENT" SP number) /
+                     ("UIDNEXT" SP nz-number) /
+                     ("UIDVALIDITY" SP nz-number) /
+                     ("UNSEEN" SP number)
+                     ;; Extensions to the STATUS responses
+                     ;; should extend this production.
+                     ;; Extensions should use the generic
+                     ;; syntax defined by tagged-ext.
+
+   store           = "STORE" SP sequence-set [store-modifiers]
+                     SP store-att-flags
+                     ;; extend [IMAP4] STORE command syntax
+                     ;; to allow for optional store-modifiers
+
+   store-modifiers =  SP "(" store-modifier *(SP store-modifier)
+                       ")"
+
+   store-modifier  = store-modifier-name [SP store-modif-params]
+
+   store-modif-params = tagged-ext-val
+                     ;; This non-terminal shows recommended syntax
+                     ;; for future extensions.
+
+   store-modifier-name = tagged-ext-label
+
+   tag-string         = string
+                        ;; tag of the command that caused
+                        ;; the ESEARCH response, sent as
+                        ;; a string.
+
+   tagged-ext          = tagged-ext-label SP tagged-ext-val
+                          ;; recommended overarching syntax for
+                          ;; extensions
+
+   tagged-ext-label    = tagged-label-fchar *tagged-label-char
+                         ;; Is a valid RFC 3501 "atom".
+
+   tagged-label-fchar  = ALPHA / "-" / "_" / "."
+
+   tagged-label-char   = tagged-label-fchar / DIGIT / ":"
+
+
+
+
+
+
+
+
+Melnikov & Daboo            Standards Track                    [Page 13]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+   tagged-ext-comp     = astring /
+                         tagged-ext-comp *(SP tagged-ext-comp) /
+                         "(" tagged-ext-comp ")"
+                          ;; Extensions that follow this general
+                          ;; syntax should use nstring instead of
+                          ;; astring when appropriate in the context
+                          ;; of the extension.
+                          ;; Note that a message set or a "number"
+                          ;; can always be represented as an "atom".
+                          ;; An URL should be represented as
+                          ;; a "quoted" string.
+
+   tagged-ext-simple   = sequence-set / number
+
+   tagged-ext-val      = tagged-ext-simple /
+                         "(" [tagged-ext-comp] ")"
+
+4.  Security Considerations
+
+   This document updates ABNF in RFCs 2088, 2342, 3501, 3502, and 3516.
+   The updated documents must be consulted for security considerations
+   for the extensions that they define.
+
+   As a protocol gets more complex, parser bugs become more common
+   including buffer overflow, denial of service, and other common
+   security coding errors.  To the extent that this document makes the
+   parser more complex, it makes this situation worse.  To the extent
+   that this document makes the parser more consistent and thus simpler,
+   the situation is improved.  The impact will depend on how many
+   deployed IMAP extensions are consistent with this document.
+   Implementers are encouraged to take care of these issues when
+   extending existing implementations.  Future IMAP extensions should
+   strive for consistency and simplicity to the greatest extent
+   possible.
+
+   Extensions to IMAP commands that are permitted in NOT AUTHENTICATED
+   state are more sensitive to these security issues due to the larger
+   possible attacker community prior to authentication, and the fact
+   that some IMAP servers run with elevated privileges in that state.
+   This document does not extend any commands permitted in NOT
+   AUTHENTICATED state.  Future IMAP extensions to commands permitted in
+   NOT AUTHENTICATED state should favor simplicity over consistency or
+   extensibility.
+
+
+
+
+
+
+
+
+Melnikov & Daboo            Standards Track                    [Page 14]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+5.  Normative References
+
+   [KEYWORDS]    Bradner, S., "Key words for use in RFCs to Indicate
+                 Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [IMAP4]       Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+                 VERSION 4rev1", RFC 3501, March 2003.
+
+   [ABNF]        Crocker, D., Ed., and P. Overell, "Augmented BNF for
+                 Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+   [CHARSET]     Freed, N. and J. Postel, "IANA Charset Registration
+                 Procedures", BCP 19, RFC 2978, October 2000.
+
+   [MULTIAPPEND] Crispin, M., "Internet Message Access Protocol (IMAP) -
+                 MULTIAPPEND Extension", RFC 3502, March 2003.
+
+   [NAMESPACE]   Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
+                 May 1998.
+
+   [LITERAL+]    Myers, J., "IMAP4 non-synchronizing literals", RFC
+                 2088, January 1997.
+
+   [BINARY]      Nerenberg, L., "IMAP4 Binary Content Extension", RFC
+                 3516, April 2003.
+
+6.  Acknowledgements
+
+   This documents is based on ideas proposed by Pete Resnick, Mark
+   Crispin, Ken Murchison, Philip Guenther, Randall Gellens, and Lyndon
+   Nerenberg.
+
+   However, all errors and omissions must be attributed to the authors
+   of the document.
+
+   Thanks to Philip Guenther, Dave Cridland, Mark Crispin, Chris Newman,
+   Elwyn Davies, and Barry Leiba for comments and corrections.
+
+   literal8 syntax was taken from RFC 3516.
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Daboo            Standards Track                    [Page 15]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+Authors' Addresses
+
+   Alexey Melnikov
+   Isode Limited
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex, TW12 2BX
+   UK
+
+   EMail: Alexey.Melnikov@isode.com
+
+
+   Cyrus Daboo
+
+   EMail: cyrus@daboo.name
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Daboo            Standards Track                    [Page 16]
+
+RFC 4466           Collected Extensions to IMAP4 ABNF         April 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Melnikov & Daboo            Standards Track                    [Page 17]
+
diff --git a/imap/docs/rfc/rfc4467.txt b/imap/docs/rfc/rfc4467.txt
new file mode 100644
index 00000000..83b6516a
--- /dev/null
+++ b/imap/docs/rfc/rfc4467.txt
@@ -0,0 +1,1011 @@
+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 4467                      University of Washington
+Updates: 3501                                                   May 2006
+Category: Standards Track
+
+
+      Internet Message Access Protocol (IMAP) - URLAUTH Extension
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   This document describes the URLAUTH extension to the Internet Message
+   Access Protocol (IMAP) (RFC 3501) and the IMAP URL Scheme (IMAPURL)
+   (RFC 2192).  This extension provides a means by which an IMAP client
+   can use URLs carrying authorization to access limited message data on
+   the IMAP server.
+
+   An IMAP server that supports this extension indicates this with a
+   capability name of "URLAUTH".
+
+1.  Introduction
+
+   In [IMAPURL], a URL of the form imap://fred@example.com/INBOX/;uid=20
+   requires authorization as userid "fred".  However, [IMAPURL] implies
+   that it only supports authentication and confuses the concepts of
+   authentication and authorization.
+
+   The URLAUTH extension defines an authorization mechanism for IMAP
+   URLs to replace [IMAPURL]'s authentication-only mechanism.  URLAUTH
+   conveys authorization in the URL string itself and reuses a portion
+   of the syntax of the [IMAPURL] authentication mechanism to convey the
+   authorization identity (which also defines the default namespace in
+   [IMAP]).
+
+   The URLAUTH extension provides a means by which an authorized user of
+   an IMAP server can create URLAUTH-authorized IMAP URLs.  A URLAUTH-
+   authorized URL conveys authorization (not authentication) to the data
+
+
+
+Crispin                     Standards Track                     [Page 1]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+   addressed by that URL.  This URL can be used in another IMAP session
+   to access specific content on the IMAP server, without otherwise
+   providing authorization to any other data (such as other data in the
+   mailbox specified in the URL) owned by the authorizing user.
+
+   Conceptually, a URLAUTH-authorized URL can be thought of as a "pawn
+   ticket" that carries no authentication information and can be
+   redeemed by whomever presents it.  However, unlike a pawn ticket,
+   URLAUTH has optional mechanisms to restrict the usage of a URLAUTH-
+   authorized URL.  Using these mechanisms, URLAUTH-authorized URLs can
+   be usable by:
+
+      . anonymous (the "pawn ticket" model)
+      . authenticated users only
+      . a specific authenticated user only
+      . message submission acting on behalf of a specific user only
+
+   There is also a mechanism for expiration.
+
+   A URLAUTH-authorized URL can be used in the argument to the BURL
+   command in message composition, as described in [BURL], for such
+   purposes as allowing a client (with limited memory or other
+   resources) to submit a message forward or to resend from an IMAP
+   mailbox without requiring the client to fetch that message data.
+
+   The URLAUTH is generated using an authorization mechanism name and an
+   authorization token, which is generated using a secret mailbox access
+   key.  An IMAP client can request that the server generate and assign
+   a new mailbox access key (thus effectively revoking all current URLs
+   using URLAUTH with the old mailbox access key) but cannot set the
+   mailbox access key to a key of its own choosing.
+
+1.1.  Conventions Used in this Document
+
+   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+   in this document are to be interpreted as defined in [KEYWORDS].
+
+   The formal syntax uses the Augmented Backus-Naur Form (ABNF) notation
+   including the core rules defined in Appendix A of [ABNF].
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.  If a single "C:" or "S:" label applies to
+   multiple lines, then the line breaks between those lines are for
+   editorial clarity only and are not part of the actual protocol
+   exchange.
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 2]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+2.  Concepts
+
+2.1.  URLAUTH
+
+   The URLAUTH is a component, appended at the end of a URL, that
+   conveys authorization to access the data addressed by that URL.  It
+   contains an authorized access identifier, an authorization mechanism
+   name, and an authorization token.  The authorization token is
+   generated from the URL, the authorized access identifier, the
+   authorization mechanism name, and a mailbox access key.
+
+2.2.  Mailbox Access Key
+
+   The mailbox access key is a random string with at least 128 bits of
+   entropy.  It is generated by software (not by the human user) and
+   MUST be unpredictable.
+
+   Each user has a table of mailboxes and an associated mailbox access
+   key for each mailbox.  Consequently, the mailbox access key is per-
+   user and per-mailbox.  In other words, two users sharing the same
+   mailbox each have a different mailbox access key for that mailbox,
+   and each mailbox accessed by a single user also has a different
+   mailbox access key.
+
+2.3.  Authorized Access Identifier
+
+   The authorized access identifier restricts use of the URLAUTH
+   authorized URL to certain users authorized on the server, as
+   described in section 3.
+
+2.4.  Authorization Mechanism
+
+   The authorization mechanism is the algorithm by which the URLAUTH is
+   generated and subsequently verified, using the mailbox access key.
+
+2.4.1.  INTERNAL Authorization Mechanism
+
+   This specification defines the INTERNAL mechanism, which uses a token
+   generation algorithm of the server's choosing and does not involve
+   disclosure of the mailbox access key to the client.
+
+      Note: The token generation algorithm chosen by the server
+      implementation should be modern and reasonably secure.  At the
+      time of the writing of this document, an [HMAC] such as HMAC-SHA1
+      is recommended.
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 3]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+      If it becomes necessary to change the token generation algorithm
+      of the INTERNAL mechanism (e.g., because an attack against the
+      current algorithm has been discovered), all currently existing
+      URLAUTH-authorized URLs are invalidated by the change in
+      algorithm.  Since this would be an unpleasant surprise to
+      applications that depend upon the validity of a URLAUTH-authorized
+      URL, and there is no good way to do a bulk update of existing
+      deployed URLs, it is best to avoid this situation by using a
+      secure algorithm as opposed to one that is "good enough".
+
+      Server implementations SHOULD consider the possibility of changing
+      the algorithm.  In some cases, it may be desirable to implement
+      the change of algorithm in a way that newly-generated tokens use
+      the new algorithm, but that for a limited period of time tokens
+      using either the new or old algorithm can be validated.
+      Consequently, the server SHOULD incorporate some means of
+      identifying the token generation algorithm within the token.
+
+   Although this specification is extensible for other mechanisms, none
+   are defined in this document.  In addition to the mechanism name
+   itself, other mechanisms may have mechanism-specific data, which is
+   to be interpreted according to the definition of that mechanism.
+
+2.5.  Authorization Token
+
+   The authorization token is a deterministic string of at least 128
+   bits that an entity with knowledge of the secret mailbox access key
+   and URL authorization mechanism can use to verify the URL.
+
+3.  IMAP URL Extensions
+
+   [IMAPURL] is extended by allowing the addition of
+   ";EXPIRE=<datetime>" and ";URLAUTH=<access>:<mech>:<token>" to IMAP
+   URLs that refer to a specific message or message parts.
+
+   The URLAUTH is comprised of ";URLAUTH=<access>:<mech>:<token>" and
+   MUST be at the end of the URL.
+
+   URLAUTH does not apply to, and MUST NOT be used with, any IMAP URL
+   that refers to an entire IMAP server, a list of mailboxes, an entire
+   IMAP mailbox, or IMAP search results.
+
+   When ";EXPIRE=<datetime>" is used, this indicates the latest date and
+   time that the URL is valid.  After that date and time, the URL has
+   expired, and server implementations MUST reject the URL.  If
+   ";EXPIRE=<datetime>" is not used, the URL has no expiration, but
+   still can be revoked as discussed below.
+
+
+
+
+Crispin                     Standards Track                     [Page 4]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+   The URLAUTH takes the form ";URLAUTH=<access>:<mech>:<token>".  It is
+   composed of three parts.  The <access> portion provides the
+   authorized access identifiers, which may constrain the operations and
+   users that are permitted to use this URL.  The <mech> portion
+   provides the authorization mechanism used by the IMAP server to
+   generate the authorization token that follows.  The <token> portion
+   provides the authorization token.
+
+   The "submit+" access identifier prefix, followed by a userid,
+   indicates that only a userid authorized as a message submission
+   entity on behalf of the specified userid is permitted to use this
+   URL.  The IMAP server does not validate the specified userid but does
+   validate that the IMAP session has an authorization identity that is
+   authorized as a message submission entity.  The authorized message
+   submission entity MUST validate the userid prior to contacting the
+   IMAP server.
+
+   The "user+" access identifier prefix, followed by a userid, indicates
+   that use of this URL is limited to IMAP sessions that are logged in
+   as the specified userid (that is, have authorization identity as that
+   userid).
+
+      Note: If a SASL mechanism that provides both authorization and
+      authentication identifiers is used to authenticate to the IMAP
+      server, the "user+" access identifier MUST match the authorization
+      identifier.
+
+   The "authuser" access identifier indicates that use of this URL is
+   limited to IMAP sessions that are logged in as an authorized user
+   (that is, have authorization identity as an authorized user) of that
+   IMAP server.  Use of this URL is prohibited to anonymous IMAP
+   sessions.
+
+   The "anonymous" access identifier indicates that use of this URL is
+   not restricted by session authorization identity; that is, any IMAP
+   session in authenticated or selected state (as defined in [IMAP]),
+   including anonymous sessions, may issue a URLFETCH using this URL.
+
+   The authorization token is represented as an ASCII-encoded
+   hexadecimal string, which is used to authorize the URL.  The length
+   and the calculation of the authorization token depends upon the
+   mechanism used; but, in all cases, the authorization token is at
+   least 128 bits (and therefore at least 32 hexadecimal digits).
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 5]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+4.  Discussion of URLAUTH Authorization Issues
+
+   In [IMAPURL], the userid before the "@" in the URL has two purposes:
+
+      1) It provides context for user-specific mailbox paths such as
+         "INBOX".
+
+      2) It specifies that resolution of the URL requires logging in as
+         that user and limits use of that URL to only that user.
+
+   An obvious limitation of using the same field for both purposes is
+   that the URL can only be resolved by the mailbox owner.
+
+   URLAUTH overrides the second purpose of the userid in the IMAP URL
+   and by default permits the URL to be resolved by any user permitted
+   by the access identifier.
+
+   The "user+<userid>" access identifier limits resolution of that URL
+   to a particular userid, whereas the "submit+<userid>" access
+   identifier is more general and simply requires that the session be
+   authorized by a user that has been granted a "submit" role within the
+   authentication system.  Use of either of these access identifiers
+   makes it impossible for an attacker, spying on the session, to use
+   the same URL, either directly or by submission to a message
+   submission entity.
+
+   The "authuser" and "anonymous" access identifiers do not have this
+   level of protection and should be used with caution.  These access
+   identifiers are primarily useful for public export of data from an
+   IMAP server, without requiring that it be copied to a web or
+   anonymous FTP server.  Refer to the Security Considerations for more
+   details.
+
+5.  Generation of URLAUTH-Authorized URLs
+
+   A URLAUTH-authorized URL is generated from an initial URL as follows:
+
+   An initial URL is built, ending with ";URLAUTH=<access>" but without
+   the ":<mech>:<token>" components.  An authorization mechanism is
+   selected and used to calculate the authorization token, with the
+   initial URL as the data and a secret known to the IMAP server as the
+   key.  The URLAUTH-authorized URL is generated by taking the initial
+   URL and appending ":", the URL authorization mechanism name, ":", and
+   the ASCII-encoded hexadecimal representation of the authorization
+   token.
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 6]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+      Note: ASCII-encoded hexadecimal is used instead of BASE64 because
+      a BASE64 representation may have "=" padding characters, which
+      would be problematic in a URL.
+
+   In the INTERNAL mechanism, the mailbox access key for that mailbox is
+   the secret known to the IMAP server, and a server-selected algorithm
+   is used as described in section 2.4.1.
+
+6.  Validation of URLAUTH-authorized URLs
+
+   A URLAUTH-authorized URL is validated as follows:
+
+   The URL is split at the ":" that separates "<access>" from
+   "<mech>:<token>" in the ";URLAUTH=<access>:<mech>:<token>" portion of
+   the URL.  The "<mech>:<token>" portion is first parsed and saved as
+   the authorization mechanism and the authorization token.  The URL is
+   truncated, discarding the ":" described above, to create a "rump URL"
+   (the URL minus the ":" and the "<mech>:<token>" portion).  The rump
+   URL is then analyzed to identify the mailbox.
+
+   If the mailbox cannot be identified, an authorization token is
+   calculated on the rump URL, using random "plausible" keys (selected
+   by the server) as needed, before returning a validation failure.
+   This prevents timing attacks aimed at identifying mailbox names.
+
+   If the mailbox can be identified, the authorization token is
+   calculated on the rump URL and a secret known to the IMAP server
+   using the given URL authorization mechanism.  Validation is
+   successful if, and only if, the calculated authorization token for
+   that mechanism matches the authorization token supplied in
+   ";URLAUTH=<access>:<mech>:<token>".
+
+   Removal of the ":<mech>:<token>" portion of the URL MUST be the only
+   operation applied to the URLAUTH-authorized URL to get the rump URL.
+   In particular, URL percent escape decoding and case-folding
+   (including to the domain part of the URL) MUST NOT occur.
+
+   In the INTERNAL mechanism, the mailbox access key for that mailbox is
+   used as the secret known to the IMAP server, and the same server-
+   selected algorithm used for generating URLs is used to calculate the
+   authorization token for verification.
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 7]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+7.  Additional Commands
+
+   These commands are extensions to the [IMAP] base protocol.
+
+   The section headings of these commands are intended to correspond
+   with where they would be located in the base protocol document if
+   they were part of that document.
+
+BASE.6.3.RESETKEY.  RESETKEY Command
+
+   Arguments:  optional mailbox name
+               optional mechanism name(s)
+
+   Responses:  none other than in result
+
+   Result:     OK - RESETKEY completed, URLMECH containing new data
+               NO - RESETKEY error: can't change key of that mailbox
+               BAD - command unknown or arguments invalid
+
+   The RESETKEY command has two forms.
+
+   The first form accepts a mailbox name as an argument and generates a
+   new mailbox access key for the given mailbox in the user's mailbox
+   access key table, replacing any previous mailbox access key (and
+   revoking any URLs that were authorized with a URLAUTH using that key)
+   in that table.  By default, the mailbox access key is generated for
+   the INTERNAL mechanism; other mechanisms can be specified with the
+   optional mechanism argument.
+
+   The second form, with no arguments, removes all mailbox access keys
+   in the user's mailbox access key table, revoking all URLs currently
+   authorized using URLAUTH by the user.
+
+   Any current IMAP session logged in as the user that has the mailbox
+   selected will receive an untagged OK response with the URLMECH status
+   response code (see section BASE.7.1.URLMECH for more details about
+   the URLMECH status response code).
+
+   Example:
+
+      C: a31 RESETKEY
+      S: a31 OK All keys removed
+      C: a32 RESETKEY INBOX
+      S: a32 OK [URLMECH INTERNAL] mechs
+      C: a33 RESETKEY INBOX XSAMPLE
+      S: a33 OK [URLMECH INTERNAL XSAMPLE=P34OKhO7VEkCbsiYY8rGEg==] done
+
+
+
+
+
+Crispin                     Standards Track                     [Page 8]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+BASE.6.3.GENURLAUTH.  GENURLAUTH Command
+
+      Argument:   one or more URL/mechanism pairs
+
+      Response:   untagged response: GENURLAUTH
+
+      Result:     OK - GENURLAUTH completed
+                  NO - GENURLAUTH error: can't generate a URLAUTH
+                  BAD - command unknown or arguments invalid
+
+   The GENURLAUTH command requests that the server generate a URLAUTH-
+   authorized URL for each of the given URLs using the given URL
+   authorization mechanism.
+
+   The server MUST validate each supplied URL as follows:
+
+      (1) The mailbox component of the URL MUST refer to an existing
+          mailbox.
+
+      (2) The server component of the URL MUST contain a valid userid
+          that identifies the owner of the mailbox access key table that
+          will be used to generate the URLAUTH-authorized URL.  As a
+          consequence, the iserver rule of [IMAPURL] is modified so that
+          iuserauth is mandatory.
+
+             Note: the server component of the URL is generally the
+             logged in userid and server.  If not, then the logged in
+             userid and server MUST have owner-type access to the
+             mailbox access key table owned by the userid and server
+             indicated by the server component of the URL.
+
+      (3) There is a valid access identifier that, in the case of
+          "submit+" and "user+", will contain a valid userid.  This
+          userid is not necessarily the same as the owner userid
+          described in (2).
+
+      (4) The server MAY also verify that the iuid and/or isection
+          components (if present) are valid.
+
+   If any of the above checks fail, the server MUST return a tagged BAD
+   response with the following exception.  If an invalid userid is
+   supplied as the mailbox access key owner and/or as part of the access
+   identifier, the server MAY issue a tagged OK response with a
+   generated mailbox key that always fails validation when used with a
+   URLFETCH command.  This exception prevents an attacker from
+   validating userids.
+
+
+
+
+
+Crispin                     Standards Track                     [Page 9]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+   If there is currently no mailbox access key for the given mailbox in
+   the owner's mailbox access key table, one is automatically generated.
+   That is, it is not necessary to use RESETKEY prior to first-time use
+   of GENURLAUTH.
+
+   If the command is successful, a GENURLAUTH response code is returned
+   listing the requested URLs as URLAUTH-authorized URLs.
+
+   Examples:
+
+      C: a775 GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/
+         ;section=1.2" INTERNAL
+      S: a775 BAD missing access identifier in supplied URL
+      C: a776 GENURLAUTH "imap://example.com/Shared/;uid=20/
+         ;section=1.2;urlauth=submit+fred" INTERNAL
+      S: a776 BAD missing owner username in supplied URL
+      C: a777 GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/
+         ;section=1.2;urlauth=submit+fred" INTERNAL
+      S: * GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/;section=1.2
+         ;urlauth=submit+fred:internal:91354a473744909de610943775f92038"
+      S: a777 OK GENURLAUTH completed
+
+BASE.6.3.URLFETCH.  URLFETCH Command
+
+      Argument:   one or more URLs
+
+      Response:   untagged response: URLFETCH
+
+      Result:     OK - urlfetch completed
+                  NO - urlfetch failed due to server internal error
+                  BAD - command unknown or arguments invalid
+
+   The URLFETCH command requests that the server return the text data
+   associated with the specified IMAP URLs, as described in [IMAPURL]
+   and extended by this document.  The data is returned for all
+   validated URLs, regardless of whether or not the session would
+   otherwise be able to access the mailbox containing that data via
+   SELECT or EXAMINE.
+
+      Note: This command does not require that the URL refer to the
+      selected mailbox; nor does it require that any mailbox be
+      selected.  It also does not in any way interfere with any selected
+      mailbox.
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 10]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+   The URLFETCH command effectively executes with the access of the
+   userid in the server component of the URL (which is generally the
+   userid that issued the GENURLAUTH).  By itself, the URLAUTH does NOT
+   grant access to the data; once validated, it grants whatever access
+   to the data is held by the userid in the server component of the URL.
+   That access may have changed since the GENURLAUTH was done.
+
+   The URLFETCH command MUST return an untagged URLFETCH response and a
+   tagged OK response to any URLFETCH command that is syntactically
+   valid.  A NO response indicates a server internal failure that may be
+   resolved on later retry.
+
+      Note: The possibility of a NO response is to accommodate
+      implementations that would otherwise have to issue an untagged BYE
+      with a fatal error due to an inability to respond to a valid
+      request.  In an ideal world, a server SHOULD NOT issue a NO
+      response.
+
+   The server MUST return NIL for any IMAP URL that references an entire
+   IMAP server, a list of mailboxes, an entire IMAP mailbox, or IMAP
+   search results.
+
+   Example:
+
+      Note: For clarity, this example uses the LOGIN command, which
+      SHOULD NOT be used over a non-encrypted communication path.
+
+      This example is of a submit server, obtaining a message segment
+      for a message that it has already validated was submitted by
+      "fred".
+
+      S: * OK [CAPABILITY IMAP4REV1 URLAUTH] example.com IMAP server
+      C: a001 LOGIN submitserver secret
+      S: a001 OK submitserver logged in
+      C: a002 URLFETCH "imap://joe@example.com/INBOX/;uid=20/
+         ;section=1.2;urlauth=submit+fred:internal
+         :91354a473744909de610943775f92038"
+      S: * URLFETCH "imap://joe@example.com/INBOX/;uid=20/;section=1.2
+         ;urlauth=submit+fred:internal
+         :91354a473744909de610943775f92038" {28}
+      S: Si vis pacem, para bellum.
+      S:
+      S: a002 OK URLFETCH completed
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 11]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+8.  Additional Responses
+
+   These responses are extensions to the [IMAP] base protocol.
+
+   The section headings of these responses are intended to correspond
+   with where they would be located in the base protocol document if
+   they were part of that document.
+
+BASE.7.1.URLMECH.  URLMECH Status Response Code
+
+   The URLMECH status response code is followed by a list of URL
+   authorization mechanism names.  Mechanism names other than INTERNAL
+   may be appended with an "=" and BASE64-encoded form of mechanism-
+   specific data.
+
+   This status response code is returned in an untagged OK response in
+   response to a RESETKEY, SELECT, or EXAMINE command.  In the case of
+   the RESETKEY command, this status response code can be sent in the
+   tagged OK response instead of requiring a separate untagged OK
+   response.
+
+   Example:
+
+      C: a33 RESETKEY INBOX XSAMPLE
+      S: a33 OK [URLMECH INTERNAL XSAMPLE=P34OKhO7VEkCbsiYY8rGEg==] done
+
+   In this example, the server supports the INTERNAL mechanism and an
+   experimental mechanism called XSAMPLE, which also holds some
+   mechanism-specific data (the name "XSAMPLE" is for illustrative
+   purposes only).
+
+BASE.7.4.GENURLAUTH.   GENURLAUTH Response
+
+   Contents:   One or more URLs
+
+   The GENURLAUTH response returns the URLAUTH-authorized URL(s)
+   requested by a GENURLAUTH command.
+
+   Example:
+
+      C: a777 GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/
+         ;section=1.2;urlauth=submit+fred" INTERNAL
+      S: * GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/;section=1.2
+         ;urlauth=submit+fred:internal:91354a473744909de610943775f92038"
+      S: a777 OK GENURLAUTH completed
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 12]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+BASE.7.4.URLFETCH.  URLFETCH Response
+
+   Contents:   One or more URL/nstring pairs
+
+   The URLFETCH response returns the message text data associated with
+   one or more IMAP URLs, as described in [IMAPURL] and extended by this
+   document.  This response occurs as the result of a URLFETCH command.
+
+   The returned data string is NIL if the URL is invalid for any reason
+   (including validation failure).  If the URL is valid, but the IMAP
+   fetch of the body part returned NIL (this should not happen), the
+   returned data string should be the empty string ("") and not NIL.
+
+      Note: This command does not require that the URL refer to the
+      selected mailbox; nor does it require that any mailbox be
+      selected.  It also does not in any way interfere with any selected
+      mailbox.
+
+   Example:
+
+      C: a002 URLFETCH "imap://joe@example.com/INBOX/;uid=20/
+         ;section=1.2;urlauth=submit+fred:internal
+         :91354a473744909de610943775f92038"
+      S: * URLFETCH "imap://joe@example.com/INBOX/;uid=20/;section=1.2
+         ;urlauth=submit+fred:internal
+         :91354a473744909de610943775f92038" {28}
+      S: Si vis pacem, para bellum.
+      S:
+      S: a002 OK URLFETCH completed
+
+9.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].
+
+   The following modifications are made to the Formal Syntax in [IMAP]:
+
+resetkey        = "RESETKEY" [SP mailbox *(SP mechanism)]
+
+capability      =/ "URLAUTH"
+
+command-auth    =/ resetkey / genurlauth / urlfetch
+
+resp-text-code  =/ "URLMECH" SP "INTERNAL" *(SP mechanism ["=" base64])
+
+genurlauth      = "GENURLAUTH" 1*(SP url-rump SP mechanism)
+
+genurlauth-data = "*" SP "GENURLAUTH" 1*(SP url-full)
+
+
+
+Crispin                     Standards Track                    [Page 13]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+url-full        = astring
+                     ; contains authimapurlfull as defined below
+
+url-rump        = astring
+                     ; contains authimapurlrump as defined below
+
+urlfetch        = "URLFETCH" 1*(SP url-full)
+
+urlfetch-data   = "*" SP "URLFETCH" 1*(SP url-full SP nstring)
+
+   The following extensions are made to the Formal Syntax in [IMAPURL]:
+
+authimapurl     = "imap://" enc-user [iauth] "@" hostport "/"
+                     imessagepart
+                     ; replaces "imapurl" and "iserver" rules for
+                     ; URLAUTH authorized URLs
+
+authimapurlfull = authimapurl iurlauth
+
+authimapurlrump = authimapurl iurlauth-rump
+
+enc-urlauth     = 32*HEXDIG
+
+enc-user        = 1*achar
+                     ; same as "enc_user" in RFC 2192
+
+iurlauth        = iurlauth-rump ":" mechanism ":" enc-urlauth
+
+iurlauth-rump   = [expire] ";URLAUTH=" access
+
+access          = ("submit+" enc-user) / ("user+" enc-user) /
+                    "authuser" / "anonymous"
+
+expire          = ";EXPIRE=" date-time
+                      ; date-time defined in [DATETIME]
+
+mechanism       = "INTERNAL" / 1*(ALPHA / DIGIT / "-" / ".")
+                     ; case-insensitive
+                     ; new mechanisms MUST be registered with IANA
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 14]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+10.  Security Considerations
+
+   Security considerations are discussed throughout this memo.
+
+   The mailbox access key SHOULD have at least 128 bits of entropy
+   (refer to [RANDOM] for more details) and MUST be unpredictable.
+
+   The server implementation of the INTERNAL mechanism SHOULD consider
+   the possibility of needing to change the token generation algorithm,
+   and SHOULD incorporate some means of identifying the token generation
+   algorithm within the token.
+
+   The URLMECH status response code may expose sensitive data in the
+   mechanism-specific data for mechanisms other than INTERNAL.  A server
+   implementation MUST implement a configuration that will not return a
+   URLMECH status response code unless some mechanism is provided that
+   protects the session from snooping, such as a TLS or SASL security
+   layer that provides confidentiality protection.
+
+   The calculation of an authorization token with a "plausible" key if
+   the mailbox can not be identified is necessary to avoid attacks in
+   which the server is probed to see if a particular mailbox exists on
+   the server by measuring the amount of time taken to reject a known
+   bad name versus some other name.
+
+   To protect against a computational denial-of-service attack, a server
+   MAY impose progressively longer delays on multiple URL requests that
+   fail validation.
+
+   The decision to use the "authuser" access identifier should be made
+   with caution.  An "authuser" access identifier can be used by any
+   authorized user of the IMAP server; therefore, use of this access
+   identifier should be limited to content that may be disclosed to any
+   authorized user of the IMAP server.
+
+   The decision to use the "anonymous" access identifier should be made
+   with extreme caution.  An "anonymous" access identifier can be used
+   by anyone; therefore, use of this access identifier should be limited
+   to content that may be disclosed to anyone.  Many IMAP servers do not
+   permit anonymous access; in this case, the "anonymous" access
+   identifier is equivalent to "authuser", but this MUST NOT be relied
+   upon.
+
+   Although this specification does not prohibit the theoretical
+   capability to generate a URL with a server component other than the
+   logged in userid and server, this capability should only be provided
+
+
+
+
+
+Crispin                     Standards Track                    [Page 15]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+   when the logged in userid/server has been authorized as equivalent to
+   the server component userid/server, or otherwise has access to that
+   userid/server mailbox access key table.
+
+11.  IANA Considerations
+
+   This document constitutes registration of the URLAUTH capability in
+   the imap4-capabilities registry.
+
+   URLAUTH authorization mechanisms are registered by publishing a
+   standards track or IESG-approved experimental RFC.  The registry is
+   currently located at:
+
+http://www.iana.org/assignments/urlauth-authorization-mechanism-registry
+
+   This registry is case-insensitive.
+
+   This document constitutes registration of the INTERNAL URLAUTH
+   authorization mechanism.
+
+   IMAP URLAUTH Authorization Mechanism Registry
+
+      Mechanism Name           Reference
+      --------------           ---------
+      INTERNAL                 [RFC4467]
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 16]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+12.  Normative References
+
+   [ABNF]     Crocker, D. and P. Overell, "Augmented BNF for Syntax
+              Specifications: ABNF", RFC 4234, October 2005.
+
+   [BURL]     Newman, C., "Message Submission BURL Extension", RFC 4468,
+              May 2006.
+
+   [DATETIME] Klyne, G. and C. Newman, "Date and Time on the Internet:
+              Timestamps", RFC 3339, July 2002.
+
+   [IMAP]     Crispin, M., "Internet Message Access Protocol - Version
+              4rev1", RFC 3501, March 2003.
+
+   [IMAPURL]  Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+13.  Informative References
+
+   [HMAC]     Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
+              Hashing for Message Authentication", RFC 2104, February
+              1997.
+
+   [RANDOM]   Eastlake, D., 3rd, Schiller, J., and S. Crocker,
+              "Randomness Requirements for Security", BCP 106, RFC 4086,
+              June 2005.
+
+Author's Address
+
+   Mark R. Crispin
+   Networks and Distributed Computing
+   University of Washington
+   4545 15th Avenue NE
+   Seattle, WA  98105-4527
+
+   Phone: (206) 543-5762
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 17]
+
+RFC 4467                IMAP - URLAUTH Extension                May 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Crispin                     Standards Track                    [Page 18]
+
diff --git a/imap/docs/rfc/rfc4468.txt b/imap/docs/rfc/rfc4468.txt
new file mode 100644
index 00000000..b16dcb4e
--- /dev/null
+++ b/imap/docs/rfc/rfc4468.txt
@@ -0,0 +1,787 @@
+
+
+
+
+
+
+Network Working Group                                          C. Newman
+Request for Comments: 4468                              Sun Microsystems
+Updates: 3463                                                   May 2006
+Category: Standards Track
+
+
+                   Message Submission BURL Extension
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   The submission profile of Simple Mail Transfer Protocol (SMTP)
+   provides a standard way for an email client to submit a complete
+   message for delivery.  This specification extends the submission
+   profile by adding a new BURL command that can be used to fetch
+   submission data from an Internet Message Access Protocol (IMAP)
+   server.  This permits a mail client to inject content from an IMAP
+   server into the SMTP infrastructure without downloading it to the
+   client and uploading it back to the server.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman                      Standards Track                     [Page 1]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+Table of Contents
+
+   1. Introduction ....................................................2
+   2. Conventions Used in This Document ...............................2
+   3. BURL Submission Extension .......................................3
+      3.1. SMTP Submission Extension Registration .....................3
+      3.2. BURL Transaction ...........................................3
+      3.3. The BURL IMAP Options ......................................4
+      3.4. Examples ...................................................5
+      3.5. Formal Syntax ..............................................6
+   4. 8-Bit and Binary ................................................7
+   5. Updates to RFC 3463 .............................................7
+   6. Response Codes ..................................................7
+   7. IANA Considerations .............................................9
+   8. Security Considerations .........................................9
+   9. References .....................................................11
+      9.1. Normative References ......................................11
+      9.2. Informative References ....................................12
+   Appendix A.  Acknowledgements .....................................13
+
+1.  Introduction
+
+   This specification defines an extension to the standard Message
+   Submission [RFC4409] protocol to permit data to be fetched from an
+   IMAP server at message submission time.  This MAY be used in
+   conjunction with the CHUNKING [RFC3030] mechanism so that chunks of
+   the message can come from an external IMAP server.  This provides the
+   ability to forward an email message without first downloading it to
+   the client.
+
+2.  Conventions Used in This Document
+
+   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+   in this document are to be interpreted as defined in "Key words for
+   use in RFCs to Indicate Requirement Levels" [RFC2119].
+
+   The formal syntax uses the Augmented Backus-Naur Form (ABNF)
+   [RFC4234] notation including the core rules defined in Appendix B of
+   RFC 4234.
+
+
+
+
+
+
+
+
+
+
+
+
+Newman                      Standards Track                     [Page 2]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+3.  BURL Submission Extension
+
+   This section defines the BURL submission extension.
+
+3.1.  SMTP Submission Extension Registration
+
+   1.  The name of this submission extension is "BURL".  This extends
+       the Message Submission protocol on port 587 and MUST NOT be
+       advertised by a regular SMTP [RFC2821] server on port 25 that
+       acts as a relay for incoming mail from other SMTP relays.
+
+   2.  The EHLO keyword value associated with the extension is "BURL".
+
+   3.  The BURL EHLO keyword will have zero or more arguments.  The only
+       argument defined at this time is the "imap" argument, which MUST
+       be present in order to use IMAP URLs with BURL.  Clients MUST
+       ignore other arguments after the BURL EHLO keyword unless they
+       are defined by a subsequent IETF standards track specification.
+       The arguments that appear after the BURL EHLO keyword may change
+       subsequent to the use of SMTP AUTH [RFC2554], so a server that
+       advertises BURL with no arguments prior to authentication
+       indicates that BURL is supported but authentication is required
+       to use it.
+
+   4.  This extension adds the BURL SMTP verb.  This verb is used as a
+       replacement for the DATA command and is only permitted during a
+       mail transaction after at least one successful RCPT TO.
+
+3.2.  BURL Transaction
+
+   A simple BURL transaction will consist of MAIL FROM, one or more RCPT
+   TO headers, and a BURL command with the "LAST" tag.  The BURL command
+   will include an IMAP URL pointing to a fully formed message ready for
+   injection into the SMTP infrastructure.  If PIPELINING [RFC2920] is
+   advertised, the client MAY send the entire transaction in one round
+   trip.  If no valid RCPT TO address is supplied, the BURL command will
+   simply fail, and no resolution of the BURL URL argument will be
+   performed.  If at least one valid RCPT TO address is supplied, then
+   the BURL URL argument will be resolved before the server responds to
+   the command.
+
+   A more sophisticated BURL transaction MAY occur when the server also
+   advertises CHUNKING [RFC3030].  In this case, the BURL and BDAT
+   commands may be interleaved until one of them terminates the
+   transaction with the "LAST" argument.  If PIPELINING [RFC2920] is
+   also advertised, then the client may pipeline the entire transaction
+   in one round-trip.  However, it MUST wait for the results of the
+   "LAST" BDAT or BURL command prior to initiating a new transaction.
+
+
+
+Newman                      Standards Track                     [Page 3]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+   The BURL command directs the server to fetch the data object to which
+   the URL refers and include it in the message.  If the URL fetch
+   fails, the server will fail the entire transaction.
+
+3.3.  The BURL IMAP Options
+
+   When "imap" is present in the space-separated list of arguments
+   following the BURL EHLO keyword, it indicates that the BURL command
+   supports the URLAUTH [RFC4467] extended form of IMAP URLs [RFC2192]
+   and that the submit server is configured with the necessary
+   credentials to resolve "urlauth=submit+" IMAP URLs for the submit
+   server's domain.
+
+   Subsequent to a successful SMTP AUTH command, the submission server
+   MAY indicate a prearranged trust relationship with a specific IMAP
+   server by including a BURL EHLO keyword argument of the form
+   "imap://imap.example.com".  In this case, the submission server will
+   permit a regular IMAP URL referring to messages or parts of messages
+   on imap.example.com that the user who authenticated to the submit
+   server can access.  Note that this form does not imply that the
+   submit server supports URLAUTH URLs; the submit server must advertise
+   both "imap" and "imap://imap.example.com" to indicate support for
+   both extended and non-extended URL forms.
+
+   When the submit server connects to the IMAP server, it acts as an
+   IMAP client and thus is subject to both the mandatory-to-implement
+   IMAP capabilities in Section 6.1.1 of RFC 3501, and the security
+   considerations in Section 11 of RFC 3501.  Specifically, this
+   requires that the submit server implement a configuration that uses
+   STARTTLS followed by SASL PLAIN [SASL-PLAIN] to authenticate to the
+   IMAP server.
+
+   When the submit server resolves a URLAUTH IMAP URL, it uses submit
+   server credentials when authenticating to the IMAP server.  The
+   authentication identity and password used for submit credentials MUST
+   be configurable.  The string "submit" is suggested as a default value
+   for the authentication identity, with no default for the password.
+   Typically, the authorization identity is empty in this case; thus the
+   IMAP server will derive the authorization identity from the
+   authentication identity.  If the IMAP URL uses the "submit+" access
+   identifier prefix, the submit server MUST refuse the BURL command
+   unless the userid in the URL's <access> token matches the submit
+   client's authorization identity.
+
+   When the submit server resolves a regular IMAP URL, it uses the
+   submit client's authorization identity when authenticating to the
+   IMAP server.  If both the submit client and the submit server's
+   embedded IMAP client use SASL PLAIN (or the equivalent), the submit
+
+
+
+Newman                      Standards Track                     [Page 4]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+   server SHOULD forward the client's credentials if and only if the
+   submit server knows that the IMAP server is in the same
+   administrative domain.  If the submit server supports SASL mechanisms
+   other than PLAIN, it MUST implement a configuration in which the
+   submit server's embedded IMAP client uses STARTTLS and SASL PLAIN
+   with the submit server's authentication identity and password (for
+   the respective IMAP server) and the submit client's authorization
+   identity.
+
+3.4.  Examples
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.  If a single "C:" or "S:" label applies to
+   multiple lines, then the line breaks between those lines are for
+   editorial clarity only and are not part of the actual protocol
+   exchange.
+
+   Two successful submissions (without and with pipelining) follow:
+
+   <SSL/TLS encryption layer negotiated>
+   C: EHLO potter.example.com
+   S: 250-owlry.example.com
+   S: 250-8BITMIME
+   S: 250-BURL imap
+   S: 250-AUTH PLAIN
+   S: 250-DSN
+   S: 250 ENHANCEDSTATUSCODES
+   C: AUTH PLAIN aGFycnkAaGFycnkAYWNjaW8=
+   S: 235 2.7.0 PLAIN authentication successful.
+   C: MAIL FROM:<harry@gryffindor.example.com>
+   S: 250 2.5.0 Address Ok.
+   C: RCPT TO:<ron@gryffindor.example.com>
+   S: 250 2.1.5 ron@gryffindor.example.com OK.
+   C: BURL imap://harry@gryffindor.example.com/outbox
+           ;uidvalidity=1078863300/;uid=25;urlauth=submit+harry
+           :internal:91354a473744909de610943775f92038 LAST
+   S: 250 2.5.0 Ok.
+
+   <SSL/TLS encryption layer negotiated>
+   C: EHLO potter.example.com
+   S: 250-owlry.example.com
+   S: 250-8BITMIME
+   S: 250-PIPELINING
+   S: 250-BURL imap
+   S: 250-AUTH PLAIN
+   S: 250-DSN
+   S: 250 ENHANCEDSTATUSCODES
+   C: AUTH PLAIN aGFycnkAaGFycnkAYWNjaW8=
+
+
+
+Newman                      Standards Track                     [Page 5]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+   C: MAIL FROM:<harry@gryffindor.example.com>
+   C: RCPT TO:<ron@gryffindor.example.com>
+   C: BURL imap://harry@gryffindor.example.com/outbox
+           ;uidvalidity=1078863300/;uid=25;urlauth=submit+harry
+           :internal:91354a473744909de610943775f92038 LAST
+   S: 235 2.7.0 PLAIN authentication successful.
+   S: 250 2.5.0 Address Ok.
+   S: 250 2.1.5 ron@gryffindor.example.com OK.
+   S: 250 2.5.0 Ok.
+
+   Note that PIPELINING of the AUTH command is only permitted if the
+   selected mechanism can be completed in one round trip, a client
+   initial response is provided, and no SASL security layer is
+   negotiated.  This is possible for PLAIN and EXTERNAL, but not for
+   most other SASL mechanisms.
+
+   Some examples of failure cases:
+
+   C: MAIL FROM:<harry@gryffindor.example.com>
+   C: RCPT TO:<malfoy@slitherin.example.com>
+   C: BURL imap://harry@gryffindor.example.com/outbox
+           ;uidvalidity=1078863300/;uid=25;urlauth=submit+harry
+           :internal:91354a473744909de610943775f92038 LAST
+   S: 250 2.5.0 Address Ok.
+   S: 550 5.7.1 Relaying not allowed: malfoy@slitherin.example.com
+   S: 554 5.5.0 No recipients have been specified.
+
+   C: MAIL FROM:<harry@gryffindor.example.com>
+   C: RCPT TO:<ron@gryffindor.example.com>
+   C: BURL imap://harry@gryffindor.example.com/outbox
+           ;uidvalidity=1078863300/;uid=25;urlauth=submit+harry
+           :internal:71354a473744909de610943775f92038 LAST
+   S: 250 2.5.0 Address Ok.
+   S: 250 2.1.5 ron@gryffindor.example.com OK.
+   S: 554 5.7.0 IMAP URL authorization failed
+
+3.5.  Formal Syntax
+
+   The following syntax specification inherits ABNF [RFC4234] and
+   Uniform Resource Identifiers [RFC3986].
+
+      burl-param  = "imap" / ("imap://" authority)
+                  ; parameter to BURL EHLO keyword
+
+      burl-cmd    = "BURL" SP absolute-URI [SP end-marker] CRLF
+
+      end-marker  = "LAST"
+
+
+
+
+Newman                      Standards Track                     [Page 6]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+4.  8-Bit and Binary
+
+   A submit server that advertises BURL MUST also advertise 8BITMIME
+   [RFC1652] and perform the down conversion described in that
+   specification on the resulting complete message if 8-bit data is
+   received with the BURL command and passed to a 7-bit server.  If the
+   URL argument to BURL refers to binary data, then the submit server
+   MAY refuse the command or down convert as described in Binary SMTP
+   [RFC3030].
+
+   The Submit server MAY refuse to accept a BURL command or combination
+   of BURL and BDAT commands that result in un-encoded 8-bit data in
+   mail or MIME [RFC2045] headers.  Alternatively, the server MAY accept
+   such data and down convert to MIME header encoding [RFC2047].
+
+5.  Updates to RFC 3463
+
+   SMTP or Submit servers that advertise ENHANCEDSTATUSCODES [RFC2034]
+   use enhanced status codes defined in RFC 3463 [RFC3463].  The BURL
+   extension introduces new error cases that that RFC did not consider.
+   The following additional enhanced status codes are defined by this
+   specification:
+
+   X.6.6 Message content not available
+
+      The message content could not be fetched from a remote system.
+      This may be useful as a permanent or persistent temporary
+      notification.
+
+   X.7.8 Trust relationship required
+
+      The submission server requires a configured trust relationship
+      with a third-party server in order to access the message content.
+
+6.  Response Codes
+
+   This section includes example response codes to the BURL command.
+   Other text may be used with the same response codes.  This list is
+   not exhaustive, and BURL clients MUST tolerate any valid SMTP
+   response code.  Most of these examples include the appropriate
+   enhanced status code [RFC3463].
+
+   554 5.5.0 No recipients have been specified
+
+      This response code occurs when BURL is used (for example, with
+      PIPELINING) and all RCPT TOs failed.
+
+
+
+
+
+Newman                      Standards Track                     [Page 7]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+   503 5.5.0 Valid RCPT TO required before BURL
+
+      This response code is an alternative to the previous one when BURL
+      is used (for example, with PIPELINING) and all RCPT TOs failed.
+
+   554 5.6.3 Conversion required but not supported
+
+      This response code occurs when the URL points to binary data and
+      the implementation does not support down conversion to base64.
+      This can also be used if the URL points to message data with 8-bit
+      content in headers and the server does not down convert such
+      content.
+
+   554 5.3.4 Message too big for system
+
+      The message (subsequent to URL resolution) is larger than the
+      per-message size limit for this server.
+
+   554 5.7.8 URL resolution requires trust relationship
+
+      The submit server does not have a trust relationship with the IMAP
+      server specified in the URL argument to BURL.
+
+   552 5.2.2 Mailbox full
+
+      The recipient is local, the submit server supports direct
+      delivery, and the recipient has exceeded his quota and any grace
+      period for delivery attempts.
+
+   554 5.6.6 IMAP URL resolution failed
+
+      The IMAP URLFETCH command returned an error or no data.
+
+   250 2.5.0 Waiting for additional BURL or BDAT commands
+
+      A BURL command without the "LAST" modifier was sent.  The URL for
+      this BURL command was successfully resolved, but the content will
+      not necessarily be committed to persistent storage until the rest
+      of the message content is collected.  For example, a Unix server
+      may have written the content to a queue file buffer, but may not
+      yet have performed an fsync() operation.  If the server loses
+      power, the content can still be lost.
+
+   451 4.4.1 IMAP server unavailable
+
+      The connection to the IMAP server to resolve the URL failed.
+
+
+
+
+
+Newman                      Standards Track                     [Page 8]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+   250 2.5.0 Ok.
+
+      The URL was successfully resolved, and the complete message data
+      has been committed to persistent storage.
+
+   250 2.6.4 MIME header conversion with loss performed
+
+      The URL pointed to message data that included mail or MIME headers
+      with 8-bit data.  This data was converted to MIME header encoding
+      [RFC2047], but the submit server may not have correctly guessed
+      the unlabeled character set.
+
+7.  IANA Considerations
+
+   The "BURL" SMTP extension as described in Section 3 has been
+   registered.  This registration has been marked for use by message
+   submission [RFC4409] only in the registry.
+
+8.  Security Considerations
+
+   Modern SMTP submission servers often include content-based security
+   and denial-of-service defense mechanisms such as virus filtering,
+   size limits, server-generated signatures, spam filtering, etc.
+   Implementations of BURL should fetch the URL content prior to
+   application of such content-based mechanisms in order to preserve
+   their function.
+
+   Clients that generate unsolicited bulk email or email with viruses
+   could use this mechanism to compensate for a slow link between the
+   client and submit server.  In particular, this mechanism would make
+   it feasible for a programmable cell phone or other device on a slow
+   link to become a significant source of unsolicited bulk email and/or
+   viruses.  This makes it more important for submit server vendors
+   implementing BURL to have auditing and/or defenses against such
+   denial-of-service attacks including mandatory authentication, logging
+   that associates unique client identifiers with mail transactions,
+   limits on reuse of the same IMAP URL, rate limits, recipient count
+   limits, and content filters.
+
+   Transfer of the URLAUTH [RFC4467] form of IMAP URLs in the clear can
+   expose the authorization token to network eavesdroppers.
+   Implementations that support such URLs can address this issue by
+   using a strong confidentiality protection mechanism.  For example,
+   the SMTP STARTTLS [RFC3207] and the IMAP STARTTLS [RFC3501]
+   extensions, in combination with a configuration setting that requires
+   their use with such IMAP URLs, would address this concern.
+
+
+
+
+
+Newman                      Standards Track                     [Page 9]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+   Use of a prearranged trust relationship between a submit server and a
+   specific IMAP server introduces security considerations.  A
+   compromise of the submit server should not automatically compromise
+   all accounts on the IMAP server, so trust relationships involving
+   super-user proxy credentials are strongly discouraged.  A system that
+   requires the submit server to authenticate to the IMAP server with
+   submit credentials and subsequently requires a URLAUTH URL to fetch
+   any content addresses this concern.  A trusted third party model for
+   proxy credentials (such as that provided by Kerberos 5 [RFC4120])
+   would also suffice.
+
+   When a client uses SMTP STARTTLS to send a BURL command that
+   references non-public information, there is a user expectation that
+   the entire message content will be treated confidentially.  To
+   address this expectation, the message submission server SHOULD use
+   STARTTLS or a mechanism providing equivalent data confidentiality
+   when fetching the content referenced by that URL.
+
+   A legitimate user of a submit server may try to compromise other
+   accounts on the server by providing an IMAP URLAUTH URL that points
+   to a server under that user's control that is designed to undermine
+   the security of the submit server.  For this reason, the IMAP client
+   code that the submit server uses must be robust with respect to
+   arbitrary input sizes (including large IMAP literals) and arbitrary
+   delays from the IMAP server.  Requiring a prearranged trust
+   relationship between a submit server and the IMAP server also
+   addresses this concern.
+
+   An authorized user of the submit server could set up a fraudulent
+   IMAP server and pass a URL for that server to the submit server.  The
+   submit server might then contact the fraudulent IMAP server to
+   authenticate with submit credentials and fetch content.  There are
+   several ways to mitigate this potential attack.  A submit server that
+   only uses submit credentials with a fixed set of trusted IMAP servers
+   will not be vulnerable to exposure of those credentials.  A submit
+   server can treat the IMAP server as untrusted and include defenses
+   for buffer overflows, denial-of-service slowdowns, and other
+   potential attacks.  Finally, because authentication is required to
+   use BURL, it is possible to keep a secure audit trail and use that to
+   detect and punish the offending party.
+
+
+
+
+
+
+
+
+
+
+
+Newman                      Standards Track                    [Page 10]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+9.  References
+
+9.1.  Normative References
+
+   [RFC1652]     Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
+                 Crocker, "SMTP Service Extension for
+                 8bit-MIMEtransport", RFC 1652, July 1994.
+
+   [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
+                 Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC2192]     Newman, C., "IMAP URL Scheme", RFC 2192,
+                 September 1997.
+
+   [RFC2554]     Myers, J., "SMTP Service Extension for Authentication",
+                 RFC 2554, March 1999.
+
+   [RFC2821]     Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
+                 April 2001.
+
+   [RFC3207]     Hoffman, P., "SMTP Service Extension for Secure SMTP
+                 over Transport Layer Security", RFC 3207,
+                 February 2002.
+
+   [RFC3501]     Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+                 VERSION 4rev1", RFC 3501, March 2003.
+
+   [RFC3986]     Berners-Lee, T., Fielding, R., and L. Masinter,
+                 "Uniform Resource Identifier (URI): Generic Syntax",
+                 STD 66, RFC 3986, January 2005.
+
+   [RFC4234]     Crocker, D. and P. Overell, "Augmented BNF for Syntax
+                 Specifications: ABNF", RFC 4234, October 2005.
+
+   [RFC4409]     Gellens, R. and J. Klensin, "Message Submission for
+                 Mail", RFC 4409, April 2006.
+
+   [RFC4467]     Crispin, M., "Internet Message Access Protocol (IMAP) -
+                 URLAUTH Extension", RFC 4467, May 2006.
+
+
+
+
+
+
+
+
+
+
+
+
+Newman                      Standards Track                    [Page 11]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+9.2.  Informative References
+
+   [RFC2034]     Freed, N., "SMTP Service Extension for Returning
+                 Enhanced Error Codes", RFC 2034, October 1996.
+
+   [RFC2045]     Freed, N. and N. Borenstein, "Multipurpose Internet
+                 Mail Extensions (MIME) Part One: Format of Internet
+                 Message Bodies", RFC 2045, November 1996.
+
+   [RFC2047]     Moore, K., "MIME (Multipurpose Internet Mail
+                 Extensions) Part Three: Message Header Extensions for
+                 Non-ASCII Text", RFC 2047, November 1996.
+
+   [RFC2920]     Freed, N., "SMTP Service Extension for Command
+                 Pipelining", STD 60, RFC 2920, September 2000.
+
+   [RFC3030]     Vaudreuil, G., "SMTP Service Extensions for
+                 Transmission of Large and Binary MIME Messages",
+                 RFC 3030, December 2000.
+
+   [RFC3463]     Vaudreuil, G., "Enhanced Mail System Status Codes",
+                 RFC 3463, January 2003.
+
+   [RFC4120]     Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
+                 Kerberos Network Authentication Service (V5)", RFC
+                 4120, July 2005.
+
+   [SASL-PLAIN]  Zeilenga, K., "The Plain SASL Mechanism", Work in
+                 Progress, March 2005.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman                      Standards Track                    [Page 12]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+Appendix A.  Acknowledgements
+
+   This document is a product of the lemonade WG.  Many thanks are due
+   to all the participants of that working group for their input.  Mark
+   Crispin was instrumental in the conception of this mechanism.  Thanks
+   to Randall Gellens, Alexey Melnikov, Sam Hartman, Ned Freed, Dave
+   Cridland, Peter Coates, and Mark Crispin for review comments on the
+   document.  Thanks to the RFC Editor for correcting the author's
+   grammar mistakes.  Thanks to Ted Hardie, Randall Gellens, Mark
+   Crispin, Pete Resnick, and Greg Vaudreuil for extremely interesting
+   debates comparing this proposal and alternatives.  Thanks to the
+   lemonade WG chairs Eric Burger and Glenn Parsons for concluding the
+   debate at the correct time and making sure this document got
+   completed.
+
+Author's Address
+
+   Chris Newman
+   Sun Microsystems
+   3401 Centrelake Dr., Suite 410
+   Ontario, CA  91761
+   US
+
+   EMail: chris.newman@sun.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman                      Standards Track                    [Page 13]
+
+RFC 4468           Message Submission BURL Extension            May 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Newman                      Standards Track                    [Page 14]
+
diff --git a/imap/docs/rfc/rfc4469.txt b/imap/docs/rfc/rfc4469.txt
new file mode 100644
index 00000000..da365514
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+++ b/imap/docs/rfc/rfc4469.txt
@@ -0,0 +1,731 @@
+
+
+
+
+
+
+Network Working Group                                         P. Resnick
+Request for Comments: 4469                         QUALCOMM Incorporated
+Updates: 3501, 3502                                           April 2006
+Category: Standards Track
+
+
+       Internet Message Access Protocol (IMAP) CATENATE Extension
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   The CATENATE extension to the Internet Message Access Protocol (IMAP)
+   extends the APPEND command to allow clients to create messages on the
+   IMAP server that may contain a combination of new data along with
+   parts of (or entire) messages already on the server.  Using this
+   extension, the client can catenate parts of an already existing
+   message onto a new message without having to first download the data
+   and then upload it back to the server.
+
+
+
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+
+Resnick                     Standards Track                     [Page 1]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+1.  Introduction
+
+   The CATENATE extension to the Internet Message Access Protocol (IMAP)
+   [1] allows the client to create a message on the server that can
+   include the text of messages (or parts of messages) that already
+   exist on the server without having to FETCH them and APPEND them back
+   to the server.  The CATENATE extension extends the APPEND command so
+   that, instead of a single message literal, the command can take as
+   arguments any combination of message literals (as described in IMAP
+   [1]) and message URLs (as described in the IMAP URL Scheme [2]
+   specification).  The server takes all the pieces and catenates them
+   into the output message.  The CATENATE extension can also coexist
+   with the MULTIAPPEND extension [3] to APPEND multiple messages in a
+   single command.
+
+   There are some obvious uses for the CATENATE extension.  The
+   motivating use case was to provide a way for a resource-constrained
+   client to compose a message for subsequent submission that contains
+   data that already exists in that client's IMAP store.  Because the
+   client does not have to download and re-upload potentially large
+   message parts, bandwidth and processing limitations do not have as
+   much impact.  In addition, since the client can create a message in
+   its own IMAP store, the command also addresses the desire of the
+   client to archive a copy of a sent message without having to upload
+   the message twice.  (Mechanisms for sending the message are outside
+   the scope of this document.)
+
+   The extended APPEND command can also be used to copy parts of a
+   message to another mailbox for archival purposes while getting rid of
+   undesired parts.  In environments where server storage is limited, a
+   client could get rid of large message parts by copying over only the
+   necessary parts and then deleting the original message.  The
+   mechanism could also be used to add data to a message (such as
+   prepending message header fields) or to include other data by making
+   a copy of the original and catenating the new data.
+
+2.  The CATENATE Capability
+
+   A server that supports this extension returns "CATENATE" as one of
+   the responses to the CAPABILITY command.
+
+
+
+
+
+
+
+
+
+
+
+Resnick                     Standards Track                     [Page 2]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+3.  The APPEND Command
+
+   Arguments:  mailbox name
+               (The following can be repeated in the presence of the
+               MULTIAPPEND extension [3])
+               OPTIONAL flag parenthesized list
+               OPTIONAL date/time string
+               a single message literal or one or more message parts to
+               catenate, specified as:
+                           message literal
+                           or
+                           message (or message part) URL
+
+   Responses:  OPTIONAL NO responses: BADURL, TOOBIG
+
+   Result:     OK -  append completed
+               NO -  append error: can't append to that mailbox, error
+                     in flags or date/time or message text, or can't
+                     fetch that data
+               BAD - command unknown or arguments invalid
+
+   The APPEND command concatenates all the message parts and appends
+   them as a new message to the end of the specified mailbox.  The
+   parenthesized flag list and date/time string set the flags and the
+   internal date, respectively, as described in IMAP [1].  The
+   subsequent command parameters specify the message parts that are
+   appended sequentially to the output message.
+
+   If the original form of APPEND is used, a message literal follows the
+   optional flag list and date/time string, which is appended as
+   described in IMAP [1].  If the extended form is used, "CATENATE" and
+   a parenthesized list of message literals and message URLs follows,
+   each of which is appended to the new message.  If a message literal
+   is specified (indicated by "TEXT"), the octets following the count
+   are appended.  If a message URL is specified (indicated by "URL"),
+   the octets of the body part pointed to by that URL are appended, as
+   if the literal returned in a FETCH BODY response were put in place of
+   the message part specifier.  The APPEND command does not cause the
+   \Seen flag to be set for any catenated body part.  The APPEND command
+   does not change the selected mailbox.
+
+   In the extended APPEND command, the string following "URL" is an IMAP
+   URL [2] and is interpreted according to the rules of [2].  The
+   present document only describes the behavior of the command using
+   IMAP URLs that refer to specific messages or message parts on the
+   current IMAP server from the current authenticated IMAP session.
+   Because of that, only relative IMAP message or message part URLs
+   (i.e., those having no scheme or <iserver>) are used.  The base URL
+
+
+
+Resnick                     Standards Track                     [Page 3]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+   for evaluating the relative URL is considered "imap://user@server/",
+   where "user" is the user name of the currently authenticated user and
+   "server" is the domain name of the current server.  When in the
+   selected state, the base URL is considered
+   "imap://user@server/mailbox", where "mailbox" is the encoded name of
+   the currently selected mailbox.  Additionally, since the APPEND
+   command is valid in the authenticated state of an IMAP session, no
+   further LOGIN or AUTHENTICATE command is performed for URLs specified
+   in the extended APPEND command.
+
+      Note: Use of an absolute IMAP URL or any URL that refers to
+      anything other than a message or message part from the current
+      authenticated IMAP session is outside the scope of this document
+      and would require an extension to this specification, and a server
+      implementing only this specification would return NO to such a
+      request.
+
+   The client is responsible for making sure that the catenated message
+   is in the format of an Internet Message Format (RFC 2822) [4] or
+   Multipurpose Internet Mail Extension (MIME) [5] message.  In
+   particular, when a URL is catenated, the server copies octets,
+   unchanged, from the indicated message or message part to the
+   catenated message.  It does no data conversion (e.g., MIME transfer
+   encodings) nor any verification that the data is appropriate for the
+   MIME part of the message into which it is inserted.  The client is
+   also responsible for inserting appropriate MIME boundaries between
+   body parts, and writing MIME Content-Type and Content-Transfer-
+   Encoding lines as needed in the appropriate places.
+
+   Responses behave just as the original APPEND command described in
+   IMAP [1].  If the server implements the IMAP UIDPLUS extension [6],
+   it will also return an APPENDUID response code in the tagged OK
+   response.  Two response codes are provided in Section 4 that can be
+   used in the tagged NO response if the APPEND command fails.
+
+4.  Response Codes
+
+   When a APPEND command fails, it may return a response code that
+   describes a reason for the failure.
+
+4.1.  BADURL Response
+
+   The BADURL response code is returned if the APPEND fails to process
+   one of the specified URLs.  Possible reasons for this are bad URL
+   syntax, unrecognized URL schema, invalid message UID, or invalid body
+   part.  The BADURL response code contains the first URL specified as a
+   parameter to the APPEND command that has caused the operation to
+   fail.
+
+
+
+Resnick                     Standards Track                     [Page 4]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+4.2.  TOOBIG Response
+
+   The TOOBIG response code is returned if the resulting message will
+   exceed the 4-GB IMAP message limit.  This might happen, for example,
+   if the client specifies 3 URLs for 2-GB messages.  Note that even if
+   the server doesn't return TOOBIG, it still has to be defensive
+   against misbehaving or malicious clients that try to construct a
+   message over the 4-GB limit.  The server may also wish to return the
+   TOOBIG response code if the resulting message exceeds a server-
+   specific message size limit.
+
+5.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) [7] notation.  Elements not defined here can be found in
+   the formal syntax of the ABNF [7], IMAP [1], and IMAP ABNF extensions
+   [8] specifications.  Note that capability and resp-text-code are
+   extended from the IMAP [1] specification and append-data is extended
+   from the IMAP ABNF extensions [8] specification.
+
+   append-data =/ "CATENATE" SP "(" cat-part *(SP cat-part) ")"
+
+   cat-part = text-literal / url
+
+   text-literal = "TEXT" SP literal
+
+   url = "URL" SP astring
+
+   resp-text-code =/ toobig-response-code / badurl-response-code
+
+   toobig-response-code = "TOOBIG"
+
+   badurl-response-code = "BADURL" SP url-resp-text
+
+   url-resp-text = 1*(%x01-09 /
+                      %x0B-0C /
+                      %x0E-5B /
+                      %x5D-FE) ; Any TEXT-CHAR except "]"
+
+   capability =/ "CATENATE"
+
+   The astring in the definition of url and the url-resp-text in the
+   definition of badurl-response-code each contain an imapurl as defined
+   by [2].
+
+
+
+
+
+
+
+Resnick                     Standards Track                     [Page 5]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+6.  Acknowledgements
+
+   Thanks to the members of the LEMONADE working group for their input.
+   Special thanks to Alexey Melnikov for the examples.
+
+7.  Security Considerations
+
+   The CATENATE extension does not raise any security considerations
+   that are not present for the base protocol or in the use of IMAP
+   URLs, and these issues are discussed in the IMAP [1] and IMAP URL [2]
+   documents.
+
+8.  IANA Considerations
+
+   IMAP4 capabilities are registered by publishing a standards track or
+   IESG approved experimental RFC.  The registry is currently located at
+   <http://www.iana.org/assignments/imap4-capabilities>.  This document
+   defines the CATENATE IMAP capability.  The IANA has added this
+   capability to the registry.
+
+
+
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+
+Resnick                     Standards Track                     [Page 6]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+Appendix A.  Examples
+
+   Lines not starting with "C: " or "S: " are continuations of the
+   previous lines.
+
+   The original message in examples 1 and 2 below (UID = 20) has the
+   following structure:
+
+
+      multipart/mixed MIME message with two body parts:
+
+      1.  text/plain
+
+      2.  application/x-zip-compressed
+
+   Example 1: The following example demonstrates how a CATENATE client
+   can replace an attachment in a draft message, without the need to
+   download it to the client and upload it back.
+
+   C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE
+    (URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;section=HEADER"
+    TEXT {42}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050907
+   C:  URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;section=1.MIME"
+    URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;section=1" TEXT {42}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050907
+   C:  URL "/Drafts;UIDVALIDITY=385759045/;UID=30" TEXT {44}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050907--
+   C: )
+   S: A003 OK catenate append completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick                     Standards Track                     [Page 7]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+   Example 2: The following example demonstrates how the CATENATE
+   extension can be used to replace edited text in a draft message, as
+   well as header fields for the top level message part (e.g., Subject
+   has changed).  The previous version of the draft is marked as
+   \Deleted.  Note that the server also supports the UIDPLUS extension,
+   so the APPENDUID response code is returned in the successful OK
+   response to the APPEND command.
+
+   C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE (TEXT {738}
+   S: + Ready for literal data
+   C: Return-Path: <bar@example.org>
+   C: Received: from [127.0.0.2]
+   C:           by rufus.example.org via TCP (internal) with ESMTPA;
+   C:           Thu, 11 Nov 2004 16:57:07 +0000
+   C: Message-ID: <419399E1.6000505@example.org>
+   C: Date: Thu, 12 Nov 2004 16:57:05 +0000
+   C: From: Bob Ar <bar@example.org>
+   C: X-Accept-Language: en-us, en
+   C: MIME-Version: 1.0
+   C: To: foo@example.net
+   C: Subject: About our holiday trip
+   C: Content-Type: multipart/mixed;
+   C:               boundary="------------030308070208000400050907"
+   C:
+   C: --------------030308070208000400050907
+   C: Content-Type: text/plain; charset=us-ascii; format=flowed
+   C: Content-Transfer-Encoding: 7bit
+   C:
+   C: Our travel agent has sent the updated schedule.
+   C:
+   C: Cheers,
+   C: Bob
+   C: --------------030308070208000400050907
+   C:  URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;Section=2.MIME"
+    URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;Section=2" TEXT {44}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050907--
+   C: )
+   S: A003 OK [APPENDUID 385759045 45] append Completed
+   C: A004 UID STORE 20 +FLAGS.SILENT (\Deleted)
+   S: A004 OK STORE completed
+
+
+
+
+
+
+
+
+
+Resnick                     Standards Track                     [Page 8]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+   Example 3: The following example demonstrates how the CATENATE
+   extension can be used to strip attachments.  Below, a PowerPoint
+   attachment was replaced by a small text part explaining that the
+   attachment was stripped.
+
+   C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE
+    (URL "/Drafts;UIDVALIDITY=385759045/;UID=21/;section=HEADER"
+    TEXT {42}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050903
+   C:  URL "/Drafts;UIDVALIDITY=385759045/;UID=21/;section=1.MIME"
+    URL "/Drafts;UIDVALIDITY=385759045/;UID=21/;section=1" TEXT {255}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050903
+   C: Content-type: text/plain; charset="us-ascii"
+   C: Content-transfer-encoding: 7bit
+   C:
+   C: This body part contained a Power Point presentation that was
+   C: deleted upon your request.
+   C: --------------030308070208000400050903--
+   C: )
+   S: A003 OK append Completed
+
+
+
+
+
+
+
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+
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+
+Resnick                     Standards Track                     [Page 9]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+   Example 4: The following example demonstrates a failed APPEND
+   command.  The server returns the BADURL response code to indicate
+   that one of the provided URLs is invalid.  This example also
+   demonstrates how the CATENATE extension can be used to construct a
+   digest of several messages.
+
+   C: A003 APPEND Sent (\Seen $MDNSent) CATENATE (TEXT {541}
+   S: + Ready for literal data
+   C: Return-Path: <foo@example.org>
+   C: Received: from [127.0.0.2]
+   C:           by rufus.example.org via TCP (internal) with ESMTPA;
+   C:           Thu, 11 Nov 2004 16:57:07 +0000
+   C: Message-ID: <419399E1.6000505@example.org>
+   C: Date: Thu, 21 Nov 2004 16:57:05 +0000
+   C: From: Farren Oo <foo@example.org>
+   C: X-Accept-Language: en-us, en
+   C: MIME-Version: 1.0
+   C: To: bar@example.org
+   C: Subject: Digest of the mailing list for today
+   C: Content-Type: multipart/digest;
+   C:               boundary="------------030308070208000400050904"
+   C:
+   C: --------------030308070208000400050904
+   C:  URL "/INBOX;UIDVALIDITY=785799047/;UID=11467" TEXT {42}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050904
+   C:  URL "/INBOX;UIDVALIDITY=785799047/;UID=113330/;section=1.5.9"
+    TEXT {42}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050904
+   C:  URL "/INBOX;UIDVALIDITY=785799047/;UID=11916" TEXT {44}
+   S: + Ready for literal data
+   C:
+   C: --------------030308070208000400050904--
+   C: )
+   S: A003 NO [BADURL "/INBOX;UIDVALIDITY=785799047/;UID=113330;
+   section=1.5.9"] CATENATE append has failed, one message expunged
+
+   Note that the server could have validated the URLs as they were
+   received and therefore could have returned the tagged NO response
+   with BADURL response-code in place of any continuation request after
+   the URL was received.
+
+
+
+
+
+
+
+Resnick                     Standards Track                    [Page 10]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+9.  Normative References
+
+   [1]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1",
+        RFC 3501, March 2003.
+
+   [2]  Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+   [3]  Crispin, M., "Internet Message Access Protocol (IMAP) -
+        MULTIAPPEND Extension", RFC 3502, March 2003.
+
+   [4]  Resnick, P., "Internet Message Format", RFC 2822, April 2001.
+
+   [5]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+        Extensions (MIME) Part One: Format of Internet Message Bodies",
+        RFC 2045, November 1996.
+
+   [6]  Crispin, M., "Internet Message Access Protocol (IMAP) - UIDPLUS
+        extension", RFC 4315, December 2005.
+
+   [7]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
+        Specifications: ABNF", RFC 4234, October 2005.
+
+   [8]  Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4 ABNF",
+        RFC 4466, April 2006.
+
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+Resnick                     Standards Track                    [Page 11]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+Author's Address
+
+   Peter W. Resnick
+   QUALCOMM Incorporated
+   5775 Morehouse Drive
+   San Diego, CA  92121-1714
+   US
+
+   Phone: +1 858 651 4478
+   EMail: presnick@qualcomm.com
+   URI:   http://www.qualcomm.com/~presnick/
+
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+Resnick                     Standards Track                    [Page 12]
+
+RFC 4469                IMAP CATENATE Extension               April 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Resnick                     Standards Track                    [Page 13]
+
diff --git a/imap/docs/rfc/rfc4505.txt b/imap/docs/rfc/rfc4505.txt
new file mode 100644
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+
+
+Network Working Group                                   K. Zeilenga, Ed.
+Request for Comments: 4505                           OpenLDAP Foundation
+Obsoletes: 2245                                                June 2006
+Category: Standards Track
+
+
+  Anonymous Simple Authentication and Security Layer (SASL) Mechanism
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   On the Internet, it is common practice to permit anonymous access to
+   various services.  Traditionally, this has been done with a plain-
+   text password mechanism using "anonymous" as the user name and using
+   optional trace information, such as an email address, as the
+   password.  As plain-text login commands are not permitted in new IETF
+   protocols, a new way to provide anonymous login is needed within the
+   context of the Simple Authentication and Security Layer (SASL)
+   framework.
+
+1.  Introduction
+
+   This document defines an anonymous mechanism for the Simple
+   Authentication and Security Layer ([SASL]) framework.  The name
+   associated with this mechanism is "ANONYMOUS".
+
+   Unlike many other SASL mechanisms, whose purpose is to authenticate
+   and identify the user to a server, the purpose of this SASL mechanism
+   is to allow the user to gain access to services or resources without
+   requiring the user to establish or otherwise disclose their identity
+   to the server.  That is, this mechanism provides an anonymous login
+   method.
+
+   This mechanism does not provide a security layer.
+
+   This document replaces RFC 2245.  Changes since RFC 2245 are detailed
+   in Appendix A.
+
+
+
+Zeilenga                    Standards Track                     [Page 1]
+
+RFC 4505                Anonymous SASL Mechanism               June 2006
+
+
+2.  The Anonymous Mechanism
+
+   The mechanism consists of a single message from the client to the
+   server.  The client may include in this message trace information in
+   the form of a string of [UTF-8]-encoded [Unicode] characters prepared
+   in accordance with [StringPrep] and the "trace" stringprep profile
+   defined in Section 3 of this document.  The trace information, which
+   has no semantical value, should take one of two forms: an Internet
+   email address, or an opaque string that does not contain the '@'
+   (U+0040) character and that can be interpreted by the system
+   administrator of the client's domain.  For privacy reasons, an
+   Internet email address or other information identifying the user
+   should only be used with permission from the user.
+
+   A server that permits anonymous access will announce support for the
+   ANONYMOUS mechanism and allow anyone to log in using that mechanism,
+   usually with restricted access.
+
+   A formal grammar for the client message using Augmented BNF [ABNF] is
+   provided below as a tool for understanding this technical
+   specification.
+
+      message     = [ email / token ]
+                    ;; to be prepared in accordance with Section 3
+
+      UTF1        = %x00-3F / %x41-7F ;; less '@' (U+0040)
+      UTF2        = %xC2-DF UTF0
+      UTF3        = %xE0 %xA0-BF UTF0 / %xE1-EC 2(UTF0) /
+                    %xED %x80-9F UTF0 / %xEE-EF 2(UTF0)
+      UTF4        = %xF0 %x90-BF 2(UTF0) / %xF1-F3 3(UTF0) /
+                    %xF4 %x80-8F 2(UTF0)
+      UTF0        = %x80-BF
+
+      TCHAR       = UTF1 / UTF2 / UTF3 / UTF4
+                    ;; any UTF-8 encoded Unicode character
+                    ;; except '@' (U+0040)
+
+      email       = addr-spec
+                    ;; as defined in [IMAIL]
+
+      token       = 1*255TCHAR
+
+   Note to implementors:
+      The <token> production is restricted to 255 UTF-8-encoded Unicode
+      characters.  As the encoding of a characters uses a sequence of 1
+      to 4 octets, a token may be as long as 1020 octets.
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 2]
+
+RFC 4505                Anonymous SASL Mechanism               June 2006
+
+
+3.  The "trace" Profile of "Stringprep"
+
+   This section defines the "trace" profile of [StringPrep].  This
+   profile is designed for use with the SASL ANONYMOUS Mechanism.
+   Specifically, the client is to prepare the <message> production in
+   accordance with this profile.
+
+   The character repertoire of this profile is Unicode 3.2 [Unicode].
+
+   No mapping is required by this profile.
+
+   No Unicode normalization is required by this profile.
+
+   The list of unassigned code points for this profile is that provided
+   in Appendix A of [StringPrep].  Unassigned code points are not
+   prohibited.
+
+   Characters from the following tables of [StringPrep] are prohibited:
+
+      - C.2.1 (ASCII control characters)
+      - C.2.2 (Non-ASCII control characters)
+      - C.3 (Private use characters)
+      - C.4 (Non-character code points)
+      - C.5 (Surrogate codes)
+      - C.6 (Inappropriate for plain text)
+      - C.8 (Change display properties are deprecated)
+      - C.9 (Tagging characters)
+
+   No additional characters are prohibited.
+
+   This profile requires bidirectional character checking per Section 6
+   of [StringPrep].
+
+4.  Example
+
+   Here is a sample ANONYMOUS login between an IMAP client and server.
+   In this example, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.  If such lines are wrapped without a new "C:"
+   or "S:" label, then the wrapping is for editorial clarity and is not
+   part of the command.
+
+   Note that this example uses the IMAP profile [IMAP4] of SASL.  The
+   base64 encoding of challenges and responses as well as the "+ "
+   preceding the responses are part of the IMAP4 profile, not part of
+   SASL itself.  Additionally, protocols with SASL profiles permitting
+   an initial client response will be able to avoid the extra round trip
+   below (the server response with an empty "+ ").
+
+
+
+
+Zeilenga                    Standards Track                     [Page 3]
+
+RFC 4505                Anonymous SASL Mechanism               June 2006
+
+
+   In this example, the trace information is "sirhc".
+
+      S: * OK IMAP4 server ready
+      C: A001 CAPABILITY
+      S: * CAPABILITY IMAP4 IMAP4rev1 AUTH=DIGEST-MD5 AUTH=ANONYMOUS
+      S: A001 OK done
+      C: A002 AUTHENTICATE ANONYMOUS
+      S: +
+      C: c2lyaGM=
+      S: A003 OK Welcome, trace information has been logged.
+
+5.  Security Considerations
+
+   The ANONYMOUS mechanism grants access to services and/or resources by
+   anyone.  For this reason, it should be disabled by default so that
+   the administrator can make an explicit decision to enable it.
+
+   If the anonymous user has any write privileges, a denial-of-service
+   attack is possible by filling up all available space.  This can be
+   prevented by disabling all write access by anonymous users.
+
+   If anonymous users have read and write access to the same area, the
+   server can be used as a communication mechanism to exchange
+   information anonymously.  Servers that accept anonymous submissions
+   should implement the common "drop box" model, which forbids anonymous
+   read access to the area where anonymous submissions are accepted.
+
+   If the anonymous user can run many expensive operations (e.g., an
+   IMAP SEARCH BODY command), this could enable a denial-of-service
+   attack.  Servers are encouraged to reduce the priority of anonymous
+   users or limit their resource usage.
+
+   While servers may impose a limit on the number of anonymous users,
+   note that such limits enable denial-of-service attacks and should be
+   used with caution.
+
+   The trace information is not authenticated, so it can be falsified.
+   This can be used as an attempt to get someone else in trouble for
+   access to questionable information.  Administrators investigating
+   abuse need to realize that this trace information may be falsified.
+
+   A client that uses the user's correct email address as trace
+   information without explicit permission may violate that user's
+   privacy.  Anyone who accesses an anonymous archive on a sensitive
+   subject (e.g., sexual abuse) likely has strong privacy needs.
+   Clients should not send the email address without the explicit
+   permission of the user and should offer the option of supplying no
+   trace information, thus only exposing the source IP address and time.
+
+
+
+Zeilenga                    Standards Track                     [Page 4]
+
+RFC 4505                Anonymous SASL Mechanism               June 2006
+
+
+   Anonymous proxy servers could enhance this privacy but would have to
+   consider the resulting potential denial-of-service attacks.
+
+   Anonymous connections are susceptible to man-in-the-middle attacks
+   that view or alter the data transferred.  Clients and servers are
+   encouraged to support external data security services.
+
+   Protocols that fail to require an explicit anonymous login are more
+   susceptible to break-ins given certain common implementation
+   techniques.  Specifically, Unix servers that offer user login may
+   initially start up as root and switch to the appropriate user id
+   after an explicit login command.  Normally, such servers refuse all
+   data access commands prior to explicit login and may enter a
+   restricted security environment (e.g., the Unix chroot(2) function)
+   for anonymous users.  If anonymous access is not explicitly
+   requested, the entire data access machinery is exposed to external
+   security attacks without the chance for explicit protective measures.
+   Protocols that offer restricted data access should not allow
+   anonymous data access without an explicit login step.
+
+   General [SASL] security considerations apply to this mechanism.
+
+   [StringPrep] security considerations and [Unicode] security
+   considerations discussed in [StringPrep] apply to this mechanism.
+   [UTF-8] security considerations also apply.
+
+6.  IANA Considerations
+
+   The SASL Mechanism registry [IANA-SASL] entry for the ANONYMOUS
+   mechanism has been updated by the IANA to reflect that this document
+   now provides its technical specification.
+
+      To: iana@iana.org
+      Subject: Updated Registration of SASL mechanism ANONYMOUS
+
+      SASL mechanism name: ANONYMOUS
+      Security considerations: See RFC 4505.
+      Published specification (optional, recommended): RFC 4505
+      Person & email address to contact for further information:
+           Kurt Zeilenga <Kurt@OpenLDAP.org>
+           Chris Newman <Chris.Newman@sun.com>
+      Intended usage: COMMON
+      Author/Change controller: IESG <iesg@ietf.org>
+      Note: Updates existing entry for ANONYMOUS
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 5]
+
+RFC 4505                Anonymous SASL Mechanism               June 2006
+
+
+   The [StringPrep] profile "trace", first defined in this RFC, has been
+   registered:
+
+      To: iana@iana.org
+      Subject: Initial Registration of Stringprep "trace" profile
+
+      Stringprep profile: trace
+      Published specification: RFC 4505
+      Person & email address to contact for further information:
+          Kurt Zeilenga <kurt@openldap.org>
+
+7.  Acknowledgement
+
+   This document is a revision of RFC 2245 by Chris Newman.  Portions of
+   the grammar defined in Section 1 were borrowed from RFC 3629 by
+   Francois Yergeau.
+
+   This document is a product of the IETF SASL WG.
+
+8.  Normative References
+
+   [ABNF]       Crocker, D. and P. Overell, "Augmented BNF for Syntax
+                Specifications: ABNF", RFC 4234, October 2005.
+
+   [IMAIL]      Resnick, P., "Internet Message Format", RFC 2822, April
+                2001.
+
+   [SASL]       Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
+                Authentication and Security Layer (SASL)", RFC 4422,
+                June 2006.
+
+   [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
+                Internationalized Strings ('stringprep')", RFC 3454,
+                December 2002.
+
+   [Unicode]    The Unicode Consortium, "The Unicode Standard, Version
+                3.2.0" is defined by "The Unicode Standard, Version 3.0"
+                (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5),
+                as amended by the "Unicode Standard Annex #27: Unicode
+                3.1" (http://www.unicode.org/reports/tr27/) and by the
+                "Unicode Standard Annex #28: Unicode 3.2"
+                (http://www.unicode.org/reports/tr28/).
+
+   [UTF-8]      Yergeau, F., "UTF-8, a transformation format of ISO
+                10646", RFC 3629 (also STD 63), November 2003.
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 6]
+
+RFC 4505                Anonymous SASL Mechanism               June 2006
+
+
+9.  Informative References
+
+   [IMAP4]      Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+                4rev1", RFC 3501, March 2003.
+
+   [IANA-SASL]  IANA, "SIMPLE AUTHENTICATION AND SECURITY LAYER (SASL)
+                MECHANISMS", <http://www.iana.org/assignments/sasl-
+                mechanisms>.
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
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+
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+
+
+
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+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 7]
+
+RFC 4505                Anonymous SASL Mechanism               June 2006
+
+
+Appendix A.  Changes since RFC 2245
+
+   This appendix is non-normative.
+
+   RFC 2245 allows the client to include optional trace information in
+   the form of a human readable string.  RFC 2245 restricted this string
+   to US-ASCII.  As the Internet is international, this document uses a
+   string restricted to UTF-8 encoded Unicode characters.  A
+   "stringprep" profile is defined to precisely define which Unicode
+   characters are allowed in this string.  While the string remains
+   restricted to 255 characters, the encoded length of each character
+   may now range from 1 to 4 octets.
+
+   Additionally, a number of editorial changes were made.
+
+Editor's Address
+
+   Kurt D. Zeilenga
+   OpenLDAP Foundation
+
+   EMail: Kurt@OpenLDAP.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 8]
+
+RFC 4505                Anonymous SASL Mechanism               June 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 9]
+
diff --git a/imap/docs/rfc/rfc4549.txt b/imap/docs/rfc/rfc4549.txt
new file mode 100644
index 00000000..8430ee10
--- /dev/null
+++ b/imap/docs/rfc/rfc4549.txt
@@ -0,0 +1,1963 @@
+
+
+
+
+
+
+Network Working Group                                   A. Melnikov, Ed.
+Request for Comments: 4549                                    Isode Ltd.
+Category: Informational                                        June 2006
+
+
+       Synchronization Operations for Disconnected IMAP4 Clients
+
+Status of This Memo
+
+   This memo provides information for the Internet community.  It does
+   not specify an Internet standard of any kind.  Distribution of this
+   memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   This document attempts to address some of the issues involved in
+   building a disconnected IMAP4 client.  In particular, it deals with
+   the issues of what might be called the "driver" portion of the
+   synchronization tool: the portion of the code responsible for issuing
+   the correct set of IMAP4 commands to synchronize the disconnected
+   client in the way that is most likely to make the human who uses the
+   disconnected client happy.
+
+   This note describes different strategies that can be used by
+   disconnected clients and shows how to use IMAP protocol in order to
+   minimize the time of the synchronization process.
+
+   This note also lists IMAP extensions that a server should implement
+   in order to provide better synchronization facilities to disconnected
+   clients.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                     Informational                      [Page 1]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+Table of Contents
+
+   1. Introduction ....................................................3
+      1.1. Conventions Used in This Document ..........................3
+   2. Design Principles ...............................................3
+   3. Overall Picture of Synchronization ..............................4
+   4. Mailbox Synchronization Steps and Strategies ....................7
+      4.1. Checking UID Validity ......................................7
+      4.2. Synchronizing Local Changes with the Server ................8
+           4.2.1. Uploading Messages to the Mailbox ...................8
+           4.2.2. Optimizing "move" and "copy" Operations .............9
+           4.2.3. Replaying Local Flag Changes .......................14
+           4.2.4. Processing Mailbox Compression (EXPUNGE) Requests ..15
+           4.2.5. Closing a Mailbox ..................................17
+      4.3. Details of "Normal" Synchronization of a Single Mailbox ...18
+           4.3.1. Discovering New Messages and Changes to Old
+                  Messages ...........................................18
+           4.3.2. Searching for "Interesting" Messages. ..............20
+           4.3.3. Populating Cache with "Interesting" Messages. ......21
+           4.3.4. User-Initiated Synchronization .....................22
+      4.4. Special Case: Descriptor-Only Synchronization .............22
+      4.5. Special Case: Fast New-Only Synchronization ...............23
+      4.6. Special Case: Blind FETCH .................................23
+   5. Implementation Considerations ..................................24
+      5.1. Error Recovery during Playback ............................26
+      5.2. Quality of Implementation Issues ..........................28
+      5.3. Optimizations .............................................28
+   6. IMAP Extensions That May Help ..................................30
+      6.1. CONDSTORE Extension .......................................30
+   7. Security Considerations ........................................33
+   8. References .....................................................33
+      8.1. Normative References ......................................33
+      8.2. Informative References ....................................34
+   9. Acknowledgements ...............................................34
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                     Informational                      [Page 2]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+1.  Introduction
+
+   Several recommendations presented in this document are generally
+   applicable to all types of IMAP clients.  However, this document
+   tries to concentrate on disconnected mail clients [IMAP-MODEL].  It
+   also suggests some IMAP extensions* that should be implemented by
+   IMAP servers in order to make the life of disconnected clients
+   easier.  In particular, the [UIDPLUS] extension was specifically
+   designed to streamline certain disconnected operations, like
+   expunging, uploading, and copying messages (see Sections 4.2.1,
+   4.2.2.1, and 4.2.4).
+
+   Readers of this document are also strongly advised to read RFC 2683
+   [RFC2683].
+
+   * Note that the functionality provided by the base IMAP protocol
+     [IMAP4] is sufficient to perform basic synchronization.
+
+1.1.  Conventions Used in This Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.  Long lines in examples are broken for
+   editorial clarity.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+   Let's call an IMAP command idempotent if the result of executing the
+   command twice sequentially is the same as the result of executing the
+   command just once.
+
+2.  Design Principles
+
+   All mailbox state or content information stored on the disconnected
+   client should be viewed strictly as a cache of the state of the
+   server.  The "master" state remains on the server, just as it would
+   with an interactive IMAP4 client.  The one exception to this rule is
+   that information about the state of the disconnected client's cache
+   (the state includes flag changes while offline and during scheduled
+   message uploads) remains on the disconnected client: that is, the
+   IMAP4 server is not responsible for remembering the state of the
+   disconnected IMAP4 client.
+
+   We assume that a disconnected client is a client that, for whatever
+   reason, wants to minimize the length of time that it is "on the
+   phone" to the IMAP4 server.  Often this will be because the client is
+   using a dialup connection, possibly with very low bandwidth, but
+
+
+
+Melnikov                     Informational                      [Page 3]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   sometimes it might just be that the human is in a hurry to catch an
+   airplane, or some other event beyond our control.  Whatever the
+   reason, we assume that we must make efficient use of the network
+   connection, both in the usual sense (not generating spurious traffic)
+   and in the sense that we would prefer not to have the connection
+   sitting idle while the client and/or the server is performing
+   strictly local computation or I/O.  Another, perhaps simpler way of
+   stating this is that we assume that network connections are
+   "expensive".
+
+   Practical experience with disconnected mail systems has shown that
+   there is no single synchronization strategy that is appropriate for
+   all cases.  Different humans have different preferences, and the same
+   human's preference will vary depending both on external circumstance
+   (how much of a hurry the human is in today) and on the value that the
+   human places on the messages being transferred.  The point here is
+   that there is no way that the synchronization program can guess
+   exactly what the human wants to do, so the human will have to provide
+   some guidance.
+
+   Taken together, the preceding two principles lead to the conclusion
+   that the synchronization program must make its decisions based on
+   some kind of guidance provided by the human, by selecting the
+   appropriate options in the user interface or through some sort of
+   configuration file.  Almost certainly, it should not pause for I/O
+   with the human in the middle of the synchronization process.  The
+   human will almost certainly have several different configurations for
+   the synchronization program, for different circumstances.
+
+   Since a disconnected client has no way of knowing what changes might
+   have occurred to the mailbox while it was disconnected, message
+   numbers are not useful to a disconnected client.  All disconnected
+   client operations should be performed using UIDs, so that the client
+   can be sure that it and the server are talking about the same
+   messages during the synchronization process.
+
+3.  Overall Picture of Synchronization
+
+   The basic strategy for synchronization is outlined below.  Note that
+   the real strategy may vary from one application to another or may
+   depend on a synchronization mode.
+
+   a) Process any "actions" that were pending on the client that were
+      not associated with any mailbox.  (In particular sending messages
+      composed offline with SMTP.  This is not part of IMAP
+      synchronization, but it is mentioned here for completeness.)
+
+
+
+
+
+Melnikov                     Informational                      [Page 4]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   b) Fetch the current list of "interesting" mailboxes.  (The
+      disconnected client should allow the user to skip this step
+      completely.)
+
+   c) "Client-to-server synchronization": for each IMAP "action" that
+      was pending on the client, do the following:
+
+      1) If the action implies opening a new mailbox (any operation that
+         operates on messages), open the mailbox.  Check its UID
+         validity value (see Section 4.1 for more details) returned in
+         the UIDVALIDITY response code.  If the UIDVALIDITY value
+         returned by the server differs, the client MUST empty the local
+         cache of the mailbox and remove any pending "actions" that
+         refer to UIDs in that mailbox (and consider them failed).  Note
+         that this doesn't affect actions performed on client-generated
+         fake UIDs (see Section 5).
+
+      2) Perform the action.  If the action is to delete a mailbox
+         (DELETE), make sure that the mailbox is closed first (see also
+         Section 3.4.12 of [RFC2683]).
+
+   d) "Server-to-client synchronization": for each mailbox that requires
+      synchronization, do the following:
+
+      1) Check the mailbox UIDVALIDITY (see Section 4.1 for more
+         details) with SELECT/EXAMINE/STATUS.
+
+         If UIDVALIDITY value returned by the server differs, the client
+         MUST
+
+         * empty the local cache of that mailbox;
+         * remove any pending "actions" that refer to UIDs in that
+           mailbox and consider them failed; and
+         * skip step 2-II.
+
+      2) Fetch the current "descriptors";
+
+         I)  Discover new messages.
+
+         II) Discover changes to old messages.
+
+      3) Fetch the bodies of any "interesting" messages that the client
+         doesn't already have.
+
+   e) Close all open mailboxes not required for further operations (if
+      staying online) or disconnect all open connections (if going
+      offline).
+
+
+
+
+Melnikov                     Informational                      [Page 5]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   Terms used:
+
+   "Actions" are queued requests that were made by the human to the
+   client's Mail User Agent (MUA) software while the client was
+   disconnected.
+
+   We define "descriptors" as a set of IMAP4 FETCH data items.
+   Conceptually, a message's descriptor is that set of information that
+   allows the synchronization program to decide what protocol actions
+   are necessary to bring the local cache to the desired state for this
+   message; since this decision is really up to the human, this
+   information probably includes at least a few header fields intended
+   for human consumption.  Exactly what will constitute a descriptor
+   depends on the client implementation.  At a minimum, the descriptor
+   contains the message's UID and FLAGS.  Other likely candidates are
+   the RFC822.SIZE, RFC822.HEADER, BODYSTRUCTURE, or ENVELOPE data
+   items.
+
+   Comments:
+
+   1) The list of actions should be ordered.  For example, if the human
+      deletes message A1 in mailbox A, then expunges mailbox A, and then
+      deletes message A2 in mailbox A, the human will expect that
+      message A1 is gone and that message A2 is still present but is now
+      deleted.
+
+      By processing all the actions before proceeding with
+      synchronization, we avoid having to compensate for the local MUA's
+      changes to the server's state.  That is, once we have processed
+      all the pending actions, the steps that the client must take to
+      synchronize itself will be the same no matter where the changes to
+      the server's state originated.
+
+   2) Steps a and b can be performed in parallel.  Alternatively, step a
+      can be performed after d.
+
+   3) On step b, the set of "interesting" mailboxes pretty much has to
+      be determined by the human.  What mailboxes belong to this set may
+      vary between different IMAP4 sessions with the same server,
+      client, and human.  An interesting mailbox can be a mailbox
+      returned by LSUB command (see Section 6.3.9 of [IMAP4]).  The
+      special mailbox "INBOX" SHOULD be in the default set of mailboxes
+      that the client considers interesting.  However, providing the
+      ability to ignore INBOX for a particular session or client may be
+      valuable for some mail filtering strategies.
+
+
+
+
+
+
+Melnikov                     Informational                      [Page 6]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   4) On step d-2-II, the client also finds out about changes to the
+      flags of messages that the client already has in its local cache,
+      and about messages in the local cache that no longer exist on the
+      server (i.e., messages that have been expunged).
+
+   5) "Interesting" messages are those messages that the synchronization
+      program thinks the human wants to have cached locally, based on
+      the configuration and the data retrieved in step b.
+
+   6) A disconnected IMAP client is a special case of an IMAP client, so
+      it MUST be able to handle any "unexpected" unsolicited responses,
+      like EXISTS and EXPUNGE, at any time.  The disconnected client MAY
+      ignore EXPUNGE response during "client-to-server" synchronization
+      phase (step c).
+
+   The rest of this discussion will focus primarily on the
+   synchronization issues for a single mailbox.
+
+4.  Mailbox Synchronization Steps and Strategies
+
+4.1.  Checking UID Validity
+
+   The "UID validity" of a mailbox is a number returned in an
+   UIDVALIDITY response code in an OK untagged response at mailbox
+   selection time.  The UID validity value changes between sessions when
+   UIDs fail to persist between sessions.
+
+   Whenever the client selects a mailbox, the client must compare the
+   returned UID validity value with the value stored in the local cache.
+   If the UID validity values differ, the UIDs in the client's cache are
+   no longer valid.  The client MUST then empty the local cache of that
+   mailbox and remove any pending "actions" that refer to UIDs in that
+   mailbox.  The client MAY also issue a warning to the human.  The
+   client MUST NOT cancel any scheduled uploads (i.e., APPENDs) for the
+   mailbox.
+
+   Note that UIDVALIDITY is not only returned on a mailbox selection.
+   The COPYUID and APPENDUID response codes defined in the [UIDPLUS]
+   extension (see also 4.2.2) and the UIDVALIDITY STATUS response data
+   item also contain a UIDVALIDITY value for some other mailbox.  The
+   client SHOULD behave as described in the previous paragraph (but it
+   should act on the other mailbox's cache), no matter how it obtained
+   the UIDVALIDITY value.
+
+
+
+
+
+
+
+
+Melnikov                     Informational                      [Page 7]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+4.2.  Synchronizing Local Changes with the Server
+
+4.2.1.  Uploading Messages to the Mailbox
+
+   Two of the most common examples of operations resulting in message
+   uploads are:
+
+   1) Saving a draft message
+
+   2) Copying a message between remote mailboxes on two different IMAP
+      servers or a local mailbox and a remote mailbox.
+
+   Message upload is performed with the APPEND command.  A message
+   scheduled to be uploaded has no UID associated with it, as all UIDs
+   are assigned by the server.  The APPEND command will effectively
+   associate a UID with the uploaded message that can be stored in the
+   local cache for future reference.  However, [IMAP4] doesn't describe
+   a simple mechanism to discover the message UID by just performing the
+   APPEND command.  In order to discover the UID, the client can do one
+   of the following:
+
+   1) Remove the uploaded message from cache.  Then, use the mechanism
+      described in 4.3 to fetch the information about the uploaded
+      message as if it had been uploaded by some other client.
+
+   2) Try to fetch header information as described in 4.2.2 in order to
+      find a message that corresponds to the uploaded message.  One
+      strategy for doing this is described in 4.2.2.
+
+   Case 1 describes a not particularly smart client.
+
+      C: A003 APPEND Drafts (\Seen $MDNSent) {310}
+      S: + Ready for literal data
+      C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+      C: From: Fred Foobar <foobar@blt.example.COM>
+      C: Subject: afternoon meeting
+      C: To: mooch@owatagu.siam.edu
+      C: Message-Id: <B27397-0100000@blt.example.COM>
+      C: MIME-Version: 1.0
+      C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+      C:
+      C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+      C:
+      S: A003 OK APPEND Completed
+
+   Fortunately, there is a simpler way to discover the message UID in
+   the presence of the [UIDPLUS] extension:
+
+
+
+
+Melnikov                     Informational                      [Page 8]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+      C: A003 APPEND Drafts (\Seen $MDNSent) {310}
+      S: + Ready for literal data
+      C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+      C: From: Fred Foobar <foobar@blt.example.COM>
+      C: Subject: afternoon meeting
+      C: To: mooch@owatagu.siam.edu
+      C: Message-Id: <B27397-0100000@blt.example.COM>
+      C: MIME-Version: 1.0
+      C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+      C:
+      C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+      C:
+      S: A003 OK [APPENDUID 1022843275 77712] APPEND completed
+
+   The UID of the appended message is the second parameter of APPENDUID
+   response code.
+
+4.2.2.  Optimizing "move" and "copy" Operations
+
+   Practical experience with IMAP and other mailbox access protocols
+   that support multiple mailboxes suggests that moving a message from
+   one mailbox to another is an extremely common operation.
+
+4.2.2.1.  Moving a Message between Two Mailboxes on the Same Server
+
+   In IMAP4, a "move" operation between two mailboxes on the same server
+   is really a combination of a COPY operation and a STORE +FLAGS
+   (\Deleted) operation.  This makes good protocol sense for IMAP, but
+   it leaves a simple-minded disconnected client in the silly position
+   of deleting and possibly expunging its cached copy of a message, then
+   fetching an identical copy via the network.
+
+   However, the presence of the UIDPLUS extension in the server can
+   help:
+
+      C: A001 UID COPY 567,414 "Interesting Messages"
+      S: A001 OK [COPYUID 1022843275 414,567 5:6] Completed
+
+   This tells the client that the message with UID 414 in the current
+   mailbox was successfully copied to the mailbox "Interesting Messages"
+   and was given the UID 5, and that the message with UID 567 was given
+   the UID 6.
+
+   In the absence of UIDPLUS extension support in the server, the
+   following trick can be used.  By including the Message-ID: header and
+   the INTERNALDATE data item as part of the descriptor, the client can
+   check the descriptor of a "new" message against messages that are
+   already in its cache and avoid fetching the extra copy.  Of course,
+
+
+
+Melnikov                     Informational                      [Page 9]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   it's possible that the cost of checking to see if the message is
+   already in the local cache may exceed the cost of just fetching it,
+   so this technique should not be used blindly.  If the MUA implements
+   a "move" command, it makes special provisions to use this technique
+   when it knows that a copy/delete sequence is the result of a "move"
+   command.
+
+   Note that servers are not required (although they are strongly
+   encouraged with "SHOULD language") to preserve INTERNALDATE when
+   copying messages.
+
+   Also note that since it's theoretically possible for this algorithm
+   to find the wrong message (given sufficiently malignant Message-ID
+   headers), implementers should provide a way to disable this
+   optimization, both permanently and on a message-by-message basis.
+
+   Example 1: Copying a message in the absence of UIDPLUS extension.
+
+   At some point in time the client has fetched the source message and
+   some information was cached:
+
+      C: C021 UID FETCH <uids> (BODY.PEEK[] INTERNALDATE FLAGS)
+      ...
+      S: * 27 FETCH (UID 123 INTERNALDATE "31-May-2002 05:26:59 -0600"
+          FLAGS (\Draft $MDNSent) BODY[] {1036}
+      S: ...
+      S: Message-Id: <20040903110856.22a127cd@chardonnay>
+      S: ...
+      S: ...message body...
+      S: )
+      ...
+      S: C021 OK fetch completed
+
+   Later on, the client decides to copy the message:
+
+      C: C035 UID COPY 123 "Interesting Messages"
+      S: C035 OK Completed
+
+   As the server hasn't provided the COPYUID response code, the client
+   tries the optimization described above:
+
+      C: C036 SELECT "Interesting Messages"
+      ...
+      C: C037 UID SEARCH ON 31-May-2002 HEADER
+          "Message-Id" "20040903110856.22a127cd@chardonnay"
+      S: SEARCH 12368
+      S: C037 OK completed
+
+
+
+
+Melnikov                     Informational                     [Page 10]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   Note that if the server has returned multiple UIDs in the SEARCH
+   response, the client MUST NOT use any of the returned UID.
+
+4.2.2.2.  Moving a Message from a Remote Mailbox to a Local
+
+   Moving a message from a remote mailbox to a local is done with FETCH
+   (that includes FLAGS and INTERNALDATE) followed by UID STORE <uid>
+   +FLAGS.SILENT (\Deleted):
+
+      C: A003 UID FETCH 123 (BODY.PEEK[] INTERNALDATE FLAGS)
+      S: * 27 FETCH (UID 123 INTERNALDATE "31-May-2002 05:26:59 -0600"
+          FLAGS (\Seen $MDNSent) BODY[]
+      S: ...message body...
+      S: )
+      S: A003 OK UID FETCH completed
+      C: A004 UID STORE <uid> +FLAGS.SILENT (\Deleted)
+      S: A004 STORE completed
+
+   Note that there is no reason to fetch the message during
+   synchronization if it's already in the client's cache.  Also, the
+   client SHOULD preserve delivery date in the local cache.
+
+4.2.2.3.  Moving a Message from a Local Mailbox to a Remote
+
+   Moving a message from a local mailbox to a remote is done with
+   APPEND:
+
+   C: A003 APPEND Drafts (\Seen $MDNSent) "31-May-2002 05:26:59 -0600"
+       {310}
+   S: + Ready for literal data
+   C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+   C: From: Fred Foobar <foobar@blt.example.COM>
+   C: Subject: afternoon meeting
+   C: To: mooch@owatagu.siam.edu
+   C: Message-Id: <B27397-0100000@blt.example.COM>
+   C: MIME-Version: 1.0
+   C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+   C:
+   C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+   C:
+   S: A003 OK [APPENDUID 1022843275 77712] completed
+
+   The client SHOULD specify the delivery date from the local cache in
+   the APPEND.
+
+   If the [LITERAL+] extension is available, the client can save a
+   round-trip*:
+
+
+
+
+Melnikov                     Informational                     [Page 11]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   C: A003 APPEND Drafts (\Seen $MDNSent) "31-May-2002 05:26:59 -0600"
+       {310+}
+   C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+   C: From: Fred Foobar <foobar@blt.example.COM>
+   C: Subject: afternoon meeting
+   C: To: mooch@owatagu.siam.edu
+   C: Message-Id: <B27397-0100000@blt.example.COM>
+   C: MIME-Version: 1.0
+   C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+   C:
+   C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+   C:
+   S: A003 OK [APPENDUID 1022843275 77712] completed
+
+   * Note that there is a risk that the server will reject the message
+     due to its size.  If this happens, the client will waste bandwidth
+     transferring the whole message.  If the client wouldn't have used
+     the LITERAL+, this could have been avoided:
+
+   C: A003 APPEND Drafts (\Seen $MDNSent) "31-May-2004 05:26:59 -0600"
+       {16777215}
+   S: A003 NO Sorry, message is too big
+
+4.2.2.4.  Moving a Message between Two Mailboxes on Different Servers
+
+   Moving a message between two mailbox on two different servers is a
+   combination of the operations described in 4.2.2.2 followed by the
+   operations described in 4.2.2.3.
+
+4.2.2.5.  Uploading Multiple Messages to a Remote Mailbox with
+          MULTIAPPEND
+
+   When there is a need to upload multiple messages to a remote mailbox
+   (e.g., as per 4.2.2.3), the presence of certain IMAP extensions may
+   significantly improve performance.  One of them is [MULTIAPPEND].
+
+   For some mail stores, opening a mailbox for appending might be
+   expensive.  [MULTIAPPEND] tells the server to open the mailbox once
+   (instead of opening and closing it "n" times per "n" messages to be
+   uploaded) and to keep it open while a group of messages is being
+   uploaded to the server.
+
+   Also, if the server supports both [MULTIAPPEND] and [LITERAL+]
+   extensions, the entire upload is accomplished in a single
+   command/response round-trip.
+
+
+
+
+
+
+Melnikov                     Informational                     [Page 12]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   Note: Client implementers should be aware that [MULTIAPPEND] performs
+   append of multiple messages atomically.  This means, for example, if
+   there is not enough space to save "n"-th message (or the message has
+   invalid structure and is rejected by the server) after successful
+   upload of "n-1" messages, the whole upload operation fails, and no
+   message will be saved in the mailbox.  Although this behavior might
+   be desirable in certain situations, it might not be what you want.
+   Otherwise, the client should use the regular APPEND command (Section
+   4.2.2.3), possibly utilizing the [LITERAL+] extension.  See also
+   Section 5.1 for discussions about error recovery.
+
+   Note: MULTIAPPEND can be used together with the UIDPLUS extension in
+   a way similar to what was described in Section 4.2.1.  [MULTIAPPEND]
+   extends the syntax of the APPENDUID response code to allow for
+   multiple message UIDs in the second parameter.
+
+   Example 2:
+
+   This example demonstrates the use of MULTIAPPEND together with
+   UIDPLUS (synchronization points where the client waits for
+   confirmations from the server are marked with "<--->"):
+
+   C: A003 APPEND Jan-2002 (\Seen $MDNSent) "31-May-2002 05:26:59 -0600"
+       {310}
+   <--->
+   S: + Ready for literal data
+   C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+   C: From: Fred Foobar <foobar@blt.example.COM>
+   C: Subject: afternoon meeting
+   C: To: mooch@owatagu.siam.edu
+   C: Message-Id: <B27397-0100000@blt.example.COM>
+   C: MIME-Version: 1.0
+   C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+   C:
+   C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+   C:  (\Seen) " 1-Jun-2002 22:43:04 -0800" {286}
+   <--->
+   S: + Ready for literal data
+   C: Date: Mon, 7 Feb 1994 22:43:04 -0800 (PST)
+   C: From: Joe Mooch <mooch@OWaTaGu.siam.EDU>
+   C: Subject: Re: afternoon meeting
+   C: To: foobar@blt.example.com
+   C: Message-Id: <a0434793874930@OWaTaGu.siam.EDU>
+   C: MIME-Version: 1.0
+   C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+   C:
+   C: 3:30 is fine with me.
+   C:
+
+
+
+Melnikov                     Informational                     [Page 13]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   S: A003 OK [APPENDUID 1022843275 77712,77713] completed
+
+   The upload takes 3 round-trips.
+
+   Example 3:
+
+   In this example, Example 2 was modified for the case when the server
+   supports MULTIAPPEND, LITERAL+, and UIDPLUS.  The upload takes only 1
+   round-trip.
+
+   C: A003 APPEND Jan-2002 (\Seen $MDNSent) "31-May-2002 05:26:59 -0600"
+       {310+}
+   C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+   C: From: Fred Foobar <foobar@blt.example.COM>
+   C: Subject: afternoon meeting
+   C: To: mooch@owatagu.siam.edu
+   C: Message-Id: <B27397-0100000@blt.example.COM>
+   C: MIME-Version: 1.0
+   C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+   C:
+   C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+   C:  (\Seen) " 1-Jun-2002 22:43:04 -0800" {286+}
+   C: Date: Mon, 7 Feb 1994 22:43:04 -0800 (PST)
+   C: From: Joe Mooch <mooch@OWaTaGu.siam.EDU>
+   C: Subject: Re: afternoon meeting
+   C: To: foobar@blt.example.com
+   C: Message-Id: <a0434793874930@OWaTaGu.siam.EDU>
+   C: MIME-Version: 1.0
+   C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+   C:
+   C: 3:30 is fine with me.
+   C:
+   S: A003 OK [APPENDUID 1022843275 77712,77713] completed
+
+4.2.3.  Replaying Local Flag Changes
+
+   The disconnected client uses the STORE command to synchronize local
+   flag state with the server.  The disconnected client SHOULD use
+   +FLAGS.SILENT or -FLAGS.SILENT in order to set or unset flags
+   modified by the user while offline.  The FLAGS form MUST NOT be used,
+   as there is a risk that this will overwrite flags on the server that
+   have been changed by some other client.
+
+   Example 4:
+
+   For the message with UID 15, the disconnected client stores the
+   following flags \Seen and $Highest.  The flags were modified on the
+   server by some other client: \Seen, \Answered, and $Highest.  While
+
+
+
+Melnikov                     Informational                     [Page 14]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   offline, the user requested that the $Highest flags be removed and
+   that the \Deleted flag be added.  The flag synchronization sequence
+   for the message should look like:
+
+      C: A001 UID STORE 15 +FLAGS.SILENT (\Deleted)
+      S: A001 STORE completed
+      C: A002 UID STORE 15 -FLAGS.SILENT ($Highest)
+      S: A002 STORE completed
+
+   If the disconnected client is able to store an additional binary
+   state information (or a piece of information that can take a value
+   from a predefined set of values) in the local cache of an IMAP
+   mailbox or in a local mailbox (e.g., message priority), and if the
+   server supports storing of arbitrary keywords, the client MUST use
+   keywords to store this state on the server.
+
+   Example 5:
+
+   Imagine a speculative mail client that can mark a message as one of
+   work-related ($Work), personal ($Personal), or spam ($Spam).  In
+   order to mark a message as personal, the client issues:
+
+      C: A001 UID STORE 15 +FLAGS.SILENT ($Personal)
+      S: A001 STORE completed
+      C: A002 UID STORE 15 -FLAGS.SILENT ($Work $Spam)
+      S: A002 STORE completed
+
+   In order to mark the message as not work, not personal and not spam,
+   the client issues:
+
+      C: A003 UID STORE 15 -FLAGS.SILENT ($Personal $Work $Spam)
+      S: A003 STORE completed
+
+4.2.4.  Processing Mailbox Compression (EXPUNGE) Requests
+
+   A naive disconnected client implementation that supports compressing
+   a mailbox while offline may decide to issue an EXPUNGE command to the
+   server in order to expunge messages marked \Deleted.  The problem
+   with this command during synchronization is that it permanently
+   erases all messages with the \Deleted flag set, i.e., even those
+   messages that were marked as \Deleted on the server while the user
+   was offline.  Doing this might result in an unpleasant surprise for
+   the user.
+
+   Fortunately the [UIDPLUS] extension can help in this case as well.
+   The extension introduces UID EXPUNGE command, that, unlike EXPUNGE,
+   takes a UID set parameter, that lists UIDs of all messages that can
+   be expunged.  When processing this command the server erases only
+
+
+
+Melnikov                     Informational                     [Page 15]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   messages with \Deleted flag listed in the UID list.  Thus, messages
+   not listed in the UID set will not be expunged even if they have the
+   \Deleted flag set.
+
+   Example 6:
+
+   While the user was offline, 3 messages with UIDs 7, 27, and 65 were
+   marked \Deleted when the user requested to compress the open mailbox.
+   Another client marked a message \Deleted on the server (UID 34).
+   During synchronization, the disconnected client issues:
+
+      C: A001 UID EXPUNGE 7,27,65
+      S: * ... EXPUNGE
+      S: * ... EXPUNGE
+      S: * ... EXPUNGE
+      S: A001 UID EXPUNGE completed
+
+   If another client issues UID SEARCH DELETED command (to find all
+   messages with the \Deleted flag) before and after the UID EXPUNGE, it
+   will get:
+
+   Before:
+
+      C: B001 UID SEARCH DELETED
+      S: * SEARCH 65 34 27 7
+      S: B001 UID SEARCH completed
+
+   After:
+
+      C: B002 UID SEARCH DELETED
+      S: * SEARCH 34
+      S: B002 UID SEARCH completed
+
+   In the absence of the [UIDPLUS] extension, the following sequence of
+   commands can be used as an approximation.  Note: It's possible for
+   another client to mark additional messages as deleted while this
+   sequence is being performed.  In this case, these additional messages
+   will be expunged as well.
+
+   1) Find all messages marked \Deleted on the server.
+
+      C: A001 UID SEARCH DELETED
+      S: * SEARCH 65 34 27 7
+      S: A001 UID SEARCH completed
+
+   2) Find all messages that must not be erased (for the previous
+      example the list will consist of the message with UID 34).
+
+
+
+
+Melnikov                     Informational                     [Page 16]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   3) Temporarily remove \Deleted flag on all messages found in step 2.
+
+      C: A002 UID STORE 34 -FLAGS.SILENT (\Deleted)
+      S: A002 UID STORE completed
+
+   4) Expunge the mailbox.
+
+      C: A003 EXPUNGE
+      S: * 20 EXPUNGE
+      S: * 7 EXPUNGE
+      S: * 1 EXPUNGE
+      S: A003 EXPUNGE completed
+
+      Here, the message with UID 7 has message number 1, with UID 27 has
+      message number 7, and with UID 65 has message number 20.
+
+   5) Restore \Deleted flag on all messages found when performing step
+      2.
+
+      C: A004 UID STORE 34 +FLAGS.SILENT (\Deleted)
+      S: A004 UID STORE completed
+
+4.2.5.  Closing a Mailbox
+
+   When the disconnected client has to close a mailbox, it should not
+   use the CLOSE command, because CLOSE does a silent EXPUNGE.  (Section
+   4.2.4 explains why EXPUNGE should not be used by a disconnected
+   client.)  It is safe to use CLOSE only if the mailbox was opened with
+   EXAMINE.
+
+   If the mailbox was opened with SELECT, the client can use one of the
+   following commands to implicitly close the mailbox and prevent the
+   silent expunge:
+
+   1) UNSELECT - This is a command described in [UNSELECT] that works as
+      CLOSE, but doesn't cause the silent EXPUNGE.  This command is
+      supported by the server if it reports UNSELECT in its CAPABILITY
+      list.
+
+   2) SELECT <another_mailbox> - SELECT causes implicit CLOSE without
+      EXPUNGE.
+
+   3) If the client intends to issue LOGOUT after closing the mailbox,
+      it may just issue LOGOUT, because LOGOUT causes implicit CLOSE
+      without EXPUNGE as well.
+
+   4) SELECT <non_existing_mailbox> - If the client knows a mailbox that
+      doesn't exist or can't be selected, it MAY SELECT it.
+
+
+
+Melnikov                     Informational                     [Page 17]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   If the client opened the mailbox with SELECT and just wants to avoid
+   implicit EXPUNGE without closing the mailbox, it may also use the
+   following:
+
+   5) EXAMINE <mailbox> - Reselect the same mailbox in read-only mode.
+
+4.3.  Details of "Normal" Synchronization of a Single Mailbox
+
+   The most common form of synchronization is where the human trusts the
+   integrity of the client's copy of the state of a particular mailbox
+   and simply wants to bring the client's cache up to date so that it
+   accurately reflects the mailbox's current state on the server.
+
+4.3.1.  Discovering New Messages and Changes to Old Messages
+
+   Let <lastseenuid> represent the highest UID that the client knows
+   about in this mailbox.  Since UIDs are allocated in strictly
+   ascending order, this is simply the UID of the last message in the
+   mailbox that the client knows about.  Let <lastseenuid+1> represent
+   <lastseenuid>'s UID plus one.  Let <descriptors> represent a list
+   consisting of all the FETCH data item items that the implementation
+   considers part of the descriptor; at a minimum this is just the FLAGS
+   data item, but it usually also includes BODYSTRUCTURE and
+   RFC822.SIZE.  At this step, <descriptors> SHOULD NOT include RFC822.
+
+   With no further information, the client can issue the following two
+   commands:
+
+      tag1 UID FETCH <lastseenuid+1>:* <descriptors>
+      tag2 UID FETCH 1:<lastseenuid> FLAGS
+
+   The first command will request some information about "new" messages
+   (i.e., messages received by the server since the last
+   synchronization).  It will also allow the client to build a message
+   number to UID map (only for new messages).  The second command allows
+   the client to
+
+      1) update cached flags for old messages;
+
+      2) find out which old messages got expunged; and
+
+      3) build a mapping between message numbers and UIDs (for old
+         messages).
+
+   The order here is significant.  We want the server to start returning
+   the list of new message descriptors as fast as it can, so that the
+   client can start issuing more FETCH commands, so we start out by
+   asking for the descriptors of all the messages we know the client
+
+
+
+Melnikov                     Informational                     [Page 18]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   cannot possibly have cached yet.  The second command fetches the
+   information we need to determine what changes may have occurred to
+   messages that the client already has cached.  Note that the former
+   command should only be issued if the UIDNEXT value cached by the
+   client differs from the one returned by the server.  Once the client
+   has issued these two commands, there's nothing more the client can do
+   with this mailbox until the responses to the first command start
+   arriving.  A clever synchronization program might use this time to
+   fetch its local cache state from disk or to start the process of
+   synchronizing another mailbox.
+
+   The following is an example of the first FETCH:
+
+   C: A011 UID fetch 131:* (FLAGS BODYSTRUCTURE INTERNALDATE
+       RFC822.SIZE)
+
+   Note 1: The first FETCH may result in the server's sending a huge
+   volume of data.  A smart disconnected client should use message
+   ranges (see also Section 3.2.1.2 of [RFC2683]), so that the user is
+   able to execute a different operation between fetching information
+   for a group of new messages.
+
+   Example 7:
+
+   Knowing the new UIDNEXT returned by the server on SELECT or EXAMINE
+   (<uidnext>), the client can split the UID range
+   <lastseenuid+1>:<uidnext> into groups, e.g., 100 messages.  After
+   that, the client can issue:
+
+      C: A011 UID fetch <lastseenuid+1>:<lastseenuid+100>
+          (FLAGS BODYSTRUCTURE INTERNALDATE RFC822.SIZE)
+      ...
+      C: A012 UID fetch <lastseenuid+101>:<lastseenuid+200>
+          (FLAGS BODYSTRUCTURE INTERNALDATE RFC822.SIZE)
+      ...
+      ...
+      C: A0FF UID fetch <lastseenuid+901>:<uidnext>
+          (FLAGS BODYSTRUCTURE INTERNALDATE RFC822.SIZE)
+
+   Note that unless a SEARCH command is issued, it is impossible to
+   determine how many messages will fall into a subrange, as UIDs are
+   not necessarily contiguous.
+
+   Note 2: The client SHOULD ignore any unsolicited EXPUNGE responses
+   received during the first FETCH command.  EXPUNGE responses contain
+   message numbers that are useless to a client that doesn't have the
+   message-number-to-UID translation table.
+
+
+
+
+Melnikov                     Informational                     [Page 19]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   The second FETCH command will result in zero or more untagged fetch
+   responses.  Each response will have a corresponding UID FETCH data
+   item.  All messages that didn't have a matching untagged FETCH
+   response MUST be removed from the local cache.
+
+   For example, if the <lastseenuid> had a value 15000 and the local
+   cache contained 3 messages with the UIDs 12, 777, and 14999,
+   respectively, then after receiving the following responses from the
+   server, the client must remove the message with UID 14999 from its
+   local cache.
+
+      S: * 1 FETCH (UID 12 FLAGS (\Seen))
+      S: * 2 FETCH (UID 777 FLAGS (\Answered \Deleted))
+
+   Note 3: If the client is not interested in flag changes (i.e., the
+   client only wants to know which old messages are still on the
+   server), the second FETCH command can be substituted with:
+
+      tag2 UID SEARCH UID 1:<lastseenuid>
+
+   This command will generate less traffic.  However, an implementor
+   should be aware that in order to build the mapping table from message
+   numbers to UIDs, the output of the SEARCH command MUST be sorted
+   first, because there is no requirement for a server to return UIDs in
+   SEARCH response in any particular order.
+
+4.3.2.  Searching for "Interesting" Messages.
+
+   This step is performed entirely on the client (from the information
+   received in the step described in 4.3.1), entirely on the server, or
+   on some combination of both.  The decision on what is an
+   "interesting" message is up to the client software and the human.
+   One easy criterion that should probably be implemented in any client
+   is whether the message is "too big" for automatic retrieval, where
+   "too big" is a parameter defined in the client's configuration.
+
+   Another commonly used criterion is the age of a message.  For
+   example, the client may choose to download only messages received in
+   the last week (in this case, <date> would be today's date minus 7
+   days):
+
+      tag3 UID SEARCH UID <uidset> SINCE <date>
+
+   Keep in mind that a date search disregards time and time zone.  The
+   client can avoid doing this search if it specified INTERNALDATE in
+   <descriptors> on the step described in 4.3.1.  If the client did, it
+   can perform the local search on its message cache.
+
+
+
+
+Melnikov                     Informational                     [Page 20]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   At this step, the client also decides what kind of information about
+   a particular message to fetch from the server.  In particular, even
+   for a message that is considered "too big", the client MAY choose to
+   fetch some part(s) of it.  For example, if the message is a
+   multipart/mixed containing a text part and a MPEG attachment, there
+   is no reason for the client not to fetch the text part.  The decision
+   of which part should or should not be fetched can be based on the
+   information received in the BODYSTRUCTURE FETCH response data item
+   (i.e., if BODYSTRUCTURE was included in <descriptors> on the step
+   described in 4.3.1).
+
+4.3.3.  Populating Cache with "Interesting" Messages.
+
+   Once the client has found out which messages are "interesting", it
+   can start issuing appropriate FETCH commands for "interesting"
+   messages or parts thereof.
+
+   Note that fetching a message into the disconnected client's local
+   cache does NOT imply that the human has (or even will) read the
+   message.  Thus, the synchronization program for a disconnected client
+   should always be careful to use the .PEEK variants of the FETCH data
+   items that implicitly set the \Seen flag.
+
+   Once the last descriptor has arrived and the last FETCH command has
+   been issued, the client simply needs to process the incoming fetch
+   items and use them to update the local message cache.
+
+   In order to avoid deadlock problems, the client must give processing
+   of received messages priority over issuing new FETCH commands during
+   this synchronization process.  This may necessitate temporary local
+   queuing of FETCH requests that cannot be issued without causing a
+   deadlock.  In order to achieve the best use of the "expensive"
+   network connection, the client will almost certainly need to pay
+   careful attention to any flow-control information that it can obtain
+   from the underlying transport connection (usually a TCP connection).
+
+   Note: The requirement stated in the previous paragraph might result
+   in an unpleasant user experience, if followed blindly.  For example,
+   the user might be unwilling to wait for the client to finish
+   synchronization before starting to process the user's requests.  A
+   smart disconnected client should allow the user to perform requested
+   operations in between IMAP commands that are part of the
+   synchronization process.  See also Note 1 in Section 4.3.1.
+
+
+
+
+
+
+
+
+Melnikov                     Informational                     [Page 21]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   Example 8:
+
+   After fetching a message BODYSTRUCTURE, the client discovers a
+   complex MIME message.  Then, it decides to fetch MIME headers of the
+   nested MIME messages and some body parts.
+
+   C: A011 UID fetch 11 (BODYSTRUCTURE)
+   S: ...
+   C: A012 UID fetch 11 (BODY[HEADER] BODY[1.MIME] BODY[1.1.MIME]
+       BODY[1.2.MIME] BODY[2.MIME] BODY[3.MIME] BODY[4.MIME]
+       BODY[5.MIME] BODY[6.MIME] BODY[7.MIME] BODY[8.MIME] BODY[9.MIME]
+       BODY[10.MIME] BODY[11.MIME] BODY[12.MIME] BODY[13.MIME]
+       BODY[14.MIME] BODY[15.MIME] BODY[16.MIME] BODY[17.MIME]
+       BODY[18.MIME] BODY[19.MIME] BODY[20.MIME] BODY[21.MIME])
+   S: ...
+   C: A013 UID fetch 11 (BODY[1.1] BODY[1.2])
+   S: ...
+   C: A014 UID fetch 11 (BODY[3] BODY[4] BODY[5] BODY[6] BODY[7] BODY[8]
+       BODY[9] BODY[10] BODY[11] BODY[13] BODY[14] BODY[15] BODY[16]
+       BODY[21])
+   S: ...
+
+4.3.4.  User-Initiated Synchronization
+
+   After the client has finished the main synchronization process as
+   described in Sections 4.3.1-4.3.3, the user may optionally request
+   additional synchronization steps while the client is still online.
+   This is not any different from the process described in Sections
+   4.3.2 and 4.3.3.
+
+   Typical examples are:
+
+    1) fetch all messages selected in UI.
+    2) fetch all messages marked as \Flagged on the server.
+
+4.4.  Special Case: Descriptor-Only Synchronization
+
+   For some mailboxes, fetching the descriptors might be the entire
+   synchronization step.  Practical experience with IMAP has shown that
+   a certain class of mailboxes (e.g., "archival" mailboxes) are used
+   primarily for long-term storage of important messages that the human
+   wants to have instantly available on demand but does not want
+   cluttering up the disconnected client's cache at any other time.
+   Messages in this kind of mailbox would be fetched exclusively by
+   explicit actions queued by the local MUA.  Thus, the only
+   synchronization desirable on this kind of mailbox is fetching enough
+   descriptor information for the user to be able to identify messages
+   for subsequent download.
+
+
+
+Melnikov                     Informational                     [Page 22]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   Special mailboxes that receive messages from a high volume, low
+   priority mailing list might also be in this category, at least when
+   the human is in a hurry.
+
+4.5.  Special Case: Fast New-Only Synchronization
+
+   In some cases, the human might be in such a hurry that he or she
+   doesn't care about changes to old messages, just about new messages.
+   In this case, the client can skip the UID FETCH command that obtains
+   the flags and UIDs for old messages (1:<lastseenuid>).
+
+4.6.  Special Case: Blind FETCH
+
+   In some cases, the human may know (for whatever reason) that he or
+   she always wants to fetch any new messages in a particular mailbox,
+   unconditionally.  In this case, the client can just fetch the
+   messages themselves, rather than just the descriptors, by using a
+   command like:
+
+      tag1 UID FETCH <lastseenuid+1>:* (FLAGS BODY.PEEK[])
+
+   Note that this example ignores the fact that the messages can be
+   arbitrary long.  The disconnected client MUST always check for
+   message size before downloading, unless explicitly told otherwise.  A
+   well-behaved client should instead use something like the following:
+
+   1) Issue "tag1 UID FETCH <lastseenuid+1>:* (FLAGS RFC822.SIZE)".
+
+   2) From the message sizes returned in step 1, construct UID set
+      <required_messages>.
+
+   3) Issue "tag2 UID FETCH <required_messages> (BODY.PEEK[])".
+
+   or
+
+   1) Issue "tag1 UID FETCH <lastseenuid+1>:* (FLAGS)".
+
+   2) Construct UID set <old_uids> from the responses of step 1.
+
+   3) Issue "tag2 SEARCH UID <old_uids> SMALLER <message_limit>".
+      Construct UID set <required_messages> from the result of the
+      SEARCH command.
+
+   4) Issue "tag3 UID FETCH <required_messages> (BODY.PEEK[])".
+
+
+
+
+
+
+
+Melnikov                     Informational                     [Page 23]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   or
+
+   1) Issue "tag1 UID FETCH <lastseenuid+1>:* (FLAGS
+      BODY.PEEK[]<0.<length>>)", where <length> should be replaced with
+      the maximal message size the client is willing to download.
+
+      Note: In response to such a command, the server will only return
+      partial data if the message is longer than <length>.  It will
+      return the full message data for any message whose size is smaller
+      than or equal to <length>.  In the former case, the client will
+      not be able to extract the full MIME structure of the message from
+      the truncated data, so the client should include BODYSTRUCTURE in
+      the UID FETCH command as well.
+
+5.  Implementation Considerations
+
+   Below are listed some common implementation pitfalls that should be
+   considered when implementing a disconnected client.
+
+   1) Implementing fake UIDs on the client.
+
+      A message scheduled to be uploaded has no UID, as UIDs are
+      selected by the server.  The client may implement fake UIDs
+      internally in order to reference not-yet-uploaded messages in
+      further operations.  (For example, a message could be scheduled to
+      be uploaded, but subsequently marked as deleted or copied to
+      another mailbox).  Here, the client MUST NOT under any
+      circumstances send these fake UIDs to the server.  Also, client
+      implementers should be reminded that according to [IMAP4] a UID is
+      a 32-bit unsigned integer excluding 0.  So, both 4294967295 and
+      2147483648 are valid UIDs, and 0 and -1 are both invalid.  Some
+      disconnected mail clients have been known to send negative numbers
+      (e.g., "-1") as message UIDs to servers during synchronization.
+
+      Situation 1: The user starts composing a new message, edits it,
+      saves it, continues to edit it, and saves it again.
+
+      A disconnected client may record in its replay log (log of
+      operations to be replayed on the server during synchronization)
+      the sequence of operations as shown below.  For the purpose of
+      this situation, we assume that all draft messages are stored in
+      the mailbox called Drafts on an IMAP server.  We will also use the
+      following conventions:  <old_uid> is the UID of the intermediate
+      version of the draft when it was saved for the first time.  This
+      is a fake UID generated on the client.  <new_uid> is the UID of
+      the final version of the draft.  This is another fake UID
+      generated on the client.
+
+
+
+
+Melnikov                     Informational                     [Page 24]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+      1) APPEND Drafts (\Seen $MDNSent \Drafts) {<nnn>}
+         ...first version of the message follows...
+
+      2) APPEND Drafts (\Seen $MDNSent \Drafts) {<mmm>}
+         ...final version of the message follows...
+
+      3) STORE <old_uid> +FLAGS (\Deleted)
+
+      Step 1 corresponds to the first attempt to save the draft message,
+      step 2 corresponds to the second attempt to save the draft
+      message, and step 3 deletes the first version of the draft message
+      saved in step 1.
+
+      A naive disconnected client may send the command in step 3 without
+      replacing the fake client generated <old_uid> with the value
+      returned by the server in step 1.  A server will probably reject
+      this command, which will make the client believe that the
+      synchronization sequence has failed.
+
+   2) Section 5.1 discusses common implementation errors related to
+      error recovery during playback.
+
+   3) Don't assume that the disconnected client is the only client used
+      by the user.
+
+      Situation 2: Some clients may use the \Deleted flag as an
+      indicator that the message should not appear in the user's view.
+      Usage of the \Deleted flag for this purpose is not safe, as other
+      clients (e.g., online clients) might EXPUNGE the mailbox at any
+      time.
+
+   4) Beware of data dependencies between synchronization operations.
+
+      It might be very tempting for a client writer to perform some
+      optimizations on the playback log.  Such optimizations might
+      include removing redundant operations (for example, see
+      optimization 2 in Section 5.3), or their reordering.
+
+      It is not always safe to reorder or remove redundant operations
+      during synchronization because some operations may have
+      dependencies (as Situation 3 demonstrates).  So, if in doubt,
+      don't do this.
+
+      Situation 3: The user copies a message out of a mailbox and then
+      deletes the mailbox.
+
+
+
+
+
+
+Melnikov                     Informational                     [Page 25]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+         C: A001 SELECT Old-Mail
+         S: ...
+         C: A002 UID COPY 111 ToDo
+         S: A002 OK [COPYUID 1022843345 111 94] Copy completed
+         ...
+         C: A015 CLOSE
+         S: A015 OK Completed
+         C: A016 DELETE Old-Mail
+         S: A016 OK Mailbox deletion completed successfully
+
+      If the client performs DELETE (tag A016) first and COPY (tag A002)
+      second, then the COPY fails.  Also, the message that the user so
+      carefully copied into another mailbox has been lost.
+
+5.1.  Error Recovery during Playback
+
+   Error recovery during synchronization is one of the trickiest parts
+   to get right.  Below, we will discuss certain error conditions and
+   suggest possible choices for handling them.
+
+   1) Lost connection to the server.
+
+      The client MUST remember the current position in the playback
+      (replay) log and replay it starting from the interrupted operation
+      (the last command issued by the client, but not acknowledged by
+      the server) the next time it successfully connects to the same
+      server.  If the connection was lost while executing a non-
+      idempotent IMAP command (see the definition in Section 1), then
+      when the client is reconnected, it MUST make sure that the
+      interrupted command was indeed not executed.  If it wasn't
+      executed, the client must restart playback from the interrupted
+      command, otherwise from the following command.
+
+      Upon reconnect, care must be taken in order to properly reapply
+      logical operations that are represented by multiple IMAP commands,
+      e.g., UID EXPUNGE emulation when UID EXPUNGE is not supported by
+      the server (see Section 4.2.4).
+
+      Once the client detects that the connection to the server was
+      lost, it MUST stop replaying its log.  There are existing
+      disconnected clients that, to the great annoyance of users, pop up
+      an error dialog for each and every playback operation that fails.
+
+   2) Copying/appending messages to a mailbox that doesn't exist.  (The
+      server advertises this condition by sending the TRYCREATE response
+      code in the tagged NO response to the APPEND or COPY command.)
+
+
+
+
+
+Melnikov                     Informational                     [Page 26]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+      The user should be advised about the situation and be given one of
+      the following choices:
+
+      a) Try to recreate a mailbox.
+      b) Copy/upload messages to another mailbox.
+      c) Skip copy/upload.
+      d) Abort replay.
+
+   3) Copying messages from a mailbox that doesn't exist, or renaming or
+      getting/changing ACLs [ACL] on a mailbox that doesn't exist:
+
+      a) Skip operation.
+      b) Abort replay.
+
+   4) Deleting mailboxes or deleting/expunging messages that no longer
+      exist.
+
+      This is actually is not an error and should be ignored by the
+      client.
+
+   5) Performing operations on messages that no longer exist.
+
+      a) Skip operation.
+      b) Abort replay.
+
+      In the case of changing flags on an expunged message, the client
+      should silently ignore the error.
+
+   Note 1: Several synchronization operations map to multiple IMAP
+   commands (for example, "move" described in 4.2.2).  The client must
+   guarantee atomicity of each such multistep operation.  For example,
+   when performing a "move" between two mailboxes on the same server, if
+   the server is unable to copy messages, the client MUST NOT attempt to
+   set the \Deleted flag on the messages being copied, let alone expunge
+   them.  However, the client MAY consider that move operation to have
+   succeeded even if the server was unable to set the \Deleted flag on
+   copied messages.
+
+   Note 2: Many synchronization operations have data dependencies.  A
+   failed operation must cause all dependent operations to fail as well.
+   The client should check this and MUST NOT try to perform all
+   dependent operations blindly (unless the user corrected the original
+   problem).  For example, a message may be scheduled to be appended to
+   a mailbox on the server and later on the appended message may be
+   copied to another mailbox.  If the APPEND operation fails, the client
+   must not attempt to COPY the failed message later on.  (See also
+   Section 5, Situation 3).
+
+
+
+
+Melnikov                     Informational                     [Page 27]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+5.2.  Quality of Implementation Issues
+
+   Below, some quality of implementation issues are listed for
+   disconnected clients.  They will help to write a disconnected client
+   that works correctly, performs synchronization as quickly as possible
+   (and thus can make the user happier as well as save her some money),
+   and minimizes the server load:
+
+   1) Don't lose information.
+
+      No matter how smart your client is in other areas, if it loses
+      information, users will get very upset.
+
+   2) Don't do work unless explicitly asked.  Be flexible.  Ask all
+      questions BEFORE starting synchronization, if possible.
+
+   3) Minimize traffic.
+
+      The client MUST NOT issue a command if the client already received
+      the required information from the server.
+
+      The client MUST make use of UIDPLUS extension if it is supported
+      by the server.
+
+      See also optimization 1 in Section 5.3.
+
+   4) Minimize the number of round-trips.
+
+      Round-trips kill performance, especially on links with high
+      latency.  Sections 4.2.2.5 and 5.2 give some advice on how to
+      minimize the number of round-trips.
+
+      See also optimization 1 in Section 5.3.
+
+5.3.  Optimizations
+
+   Some useful optimizations are described in this section.  A
+   disconnected client that supports the recommendations listed below
+   will give the user a more pleasant experience.
+
+   1) The initial OK or PREAUTH responses may contain the CAPABILITY
+      response code as described in Section 7.1 of [IMAP4].  This
+      response code gives the same information as returned by the
+      CAPABILITY command*.  A disconnected client that pays attention to
+      this response code can avoid sending CAPABILITY command and will
+      save a round-trip.
+
+
+
+
+
+Melnikov                     Informational                     [Page 28]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+      * Note: Some servers report in the CAPABILITY response code
+        extensions that are only relevant in unauthenticated state or in
+        all states.  Such servers usually send another CAPABILITY
+        response code upon successful authentication using LOGIN or
+        AUTHENTICATE command (that negotiates no security layer; see
+        Section 6.2.2 of [IMAP4]).  The CAPABILITY response code sent
+        upon successful LOGIN/AUTHENTICATE might be different from the
+        CAPABILITY response code in the initial OK response, as
+        extensions only relevant for unauthenticated state will not be
+        advertised, and some additional extensions available only in
+        authenticated and/or selected state will be.
+
+   Example 9:
+
+   S: * OK [CAPABILITY IMAP4REV1 LOGIN-REFERRALS STARTTLS
+       AUTH=DIGEST-MD5 AUTH=SRP] imap.example.com ready
+   C: 2 authenticate DIGEST-MD5
+   S: 2 OK [CAPABILITY IMAP4REV1 IDLE NAMESPACE MAILBOX-REFERRALS SCAN
+       SORT THREAD=REFERENCES THREAD=ORDEREDSUBJECT MULTIAPPEND]
+       User authenticated (no layer)
+
+   2) An advanced disconnected client may choose to optimize its replay
+      log.  For example, there might be some operations that are
+      redundant (the list is not complete):
+
+      a) an EXPUNGE followed by another EXPUNGE or CLOSE;
+      b) changing flags (other than the \Deleted flag) on a message that
+         gets immediately expunged;
+      c) opening and closing the same mailbox.
+
+   When optimizing, be careful about data dependencies between commands.
+   For example, if the client is wishing to optimize (see case b, above)
+
+      tag1 UID STORE <uid1> +FLAGS (\Deleted)
+      ...
+      tag2 UID STORE <uid1> +FLAGS (\Flagged)
+      ...
+      tag3 UID COPY <uid1> "Backup"
+      ...
+      tag4 UID EXPUNGE <uid1>
+
+   it can't remove the second UID STORE command because the message is
+   being copied before it gets expunged.
+
+   In general, it might be a good idea to keep mailboxes open during
+   synchronization (see case c above), if possible.  This can be more
+   easily achieved in conjunction with optimization 3 described below.
+
+
+
+
+Melnikov                     Informational                     [Page 29]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   3) Perform some synchronization steps in parallel, if possible.
+
+      Several synchronization steps don't depend on each other and thus
+      can be performed in parallel.  Because the server machine is
+      usually more powerful than the client machine and can perform some
+      operations in parallel, this may speed up the total time of
+      synchronization.
+
+      In order to achieve such parallelization, the client will have to
+      open more than one connection to the same server.  Client writers
+      should not forget about non-trivial cost associated with
+      establishing a TCP connection and performing an authentication.
+      The disconnected client MUST NOT use one connection per mailbox.
+      In most cases, it is sufficient to have two connections.  The
+      disconnected client SHOULD avoid selecting the same mailbox in
+      more than one connection; see Section 3.1.1 of [RFC2683] for more
+      details.
+
+      Any mailbox synchronization MUST start with checking the
+      UIDVALIDITY as described in Section 4.1 of this document.  The
+      client MAY use STATUS command to check UID Validity of a non-
+      selected mailbox.  This is preferable to opening many connections
+      to the same server to perform synchronization of multiple
+      mailboxes simultaneously.  As described in Section 5.3.10 of
+      [IMAP4], this SHOULD NOT be used on the selected mailbox.
+
+6.  IMAP Extensions That May Help
+
+   The following extensions can save traffic and/or the number of
+   round-trips:
+
+   1) The use of [UIDPLUS] is discussed in Sections 4.1, 4.2.1, 4.2.2.1
+      and 4.2.4.
+
+   2) The use of the MULTIAPPEND and LITERAL+ extensions for uploading
+      messages is discussed in Section 4.2.2.5.
+
+   3) Use the CONDSTORE extension (see Section 6.1) for quick flag
+      resynchronization.
+
+6.1.  CONDSTORE Extension
+
+   An advanced disconnected mail client should use the [CONDSTORE]
+   extension when it is supported by the server.  The client must cache
+   the value from HIGHESTMODSEQ OK response code received on mailbox
+   opening and update it whenever the server sends MODSEQ FETCH data
+   items.
+
+
+
+
+Melnikov                     Informational                     [Page 30]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+   If the client receives NOMODSEQ OK untagged response instead of
+   HIGHESTMODSEQ, it MUST remove the last known HIGHESTMODSEQ value from
+   its cache and follow the more general instructions in Section 3.
+
+   When the client opens the mailbox for synchronization, it first
+   compares UIDVALIDITY as described in step d-1 in Section 3.  If the
+   cached UIDVALIDITY value matches the one returned by the server, the
+   client MUST compare the cached value of HIGHESTMODSEQ with the one
+   returned by the server.  If the cached HIGHESTMODSEQ value also
+   matches the one returned by the server, then the client MUST NOT
+   fetch flags for cached messages, as they hasn't changed.  If the
+   value on the server is higher than the cached one, the client MAY use
+   "SEARCH MODSEQ <cached-value>" to find all messages with flags
+   changed since the last time the client was online and had the mailbox
+   opened.  Alternatively, the client MAY use "FETCH 1:* (FLAGS)
+   (CHANGEDSINCE <cached-value>)".  The latter operation combines
+   searching for changed messages and fetching new information.
+
+   In all cases, the client still needs to fetch information about new
+   messages (if requested by the user) as well as discover which
+   messages have been expunged.
+
+   Step d ("Server-to-client synchronization") in Section 4 in the
+   presence of the CONDSTORE extension is amended as follows:
+
+   d) "Server-to-client synchronization" - For each mailbox that
+      requires synchronization, do the following:
+
+      1a) Check the mailbox UIDVALIDITY (see section 4.1 for more
+          details) with SELECT/EXAMINE/STATUS.
+
+          If the UIDVALIDITY value returned by the server differs, the
+          client MUST
+
+          * empty the local cache of that mailbox;
+          * "forget" the cached HIGHESTMODSEQ value for the mailbox;
+          * remove any pending "actions" that refer to UIDs in that
+            mailbox (note that this doesn't affect actions performed on
+            client-generated fake UIDs; see Section 5); and
+          * skip steps 1b and 2-II;
+
+      1b) Check the mailbox HIGHESTMODSEQ.  If the cached value is the
+          same as the one returned by the server, skip fetching message
+          flags on step 2-II, i.e., the client only has to find out
+          which messages got expunged.
+
+
+
+
+
+
+Melnikov                     Informational                     [Page 31]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+      2) Fetch the current "descriptors".
+
+         I)  Discover new messages.
+
+         II) Discover changes to old messages and flags for new messages
+             using
+             "FETCH 1:* (FLAGS) (CHANGEDSINCE <cached-value>)" or
+             "SEARCH MODSEQ <cached-value>".
+
+             Discover expunged messages; for example, using
+             "UID SEARCH 1:<lastseenuid>".  (All messages not returned
+             in this command are expunged.)
+
+      3) Fetch the bodies of any "interesting" messages that the client
+         doesn't already have.
+
+         Example 10:
+
+         The UIDVALIDITY value is the same, but the HIGHESTMODSEQ value
+         has changed on the server while the client was offline.
+
+      C: A142 SELECT INBOX
+      S: * 172 EXISTS
+      S: * 1 RECENT
+      S: * OK [UNSEEN 12] Message 12 is first unseen
+      S: * OK [UIDVALIDITY 3857529045] UIDs valid
+      S: * OK [UIDNEXT 201] Predicted next UID
+      S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+      S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+      S: * OK [HIGHESTMODSEQ 20010715194045007]
+      S: A142 OK [READ-WRITE] SELECT completed
+
+   After that, either:
+
+      C: A143 UID FETCH 1:* (FLAGS) (CHANGEDSINCE 20010715194032001)
+      S: * 2 FETCH (UID 6 MODSEQ (20010715205008000) FLAGS (\Deleted))
+      S: * 5 FETCH (UID 9 MODSEQ (20010715195517000) FLAGS ($NoJunk
+          $AutoJunk $MDNSent))
+         ...
+      S: A143 OK FETCH completed
+
+   or:
+
+
+
+
+
+
+
+
+
+Melnikov                     Informational                     [Page 32]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+      C: A143 UID SEARCH MODSEQ 20010715194032001 UID 1:20
+      S: * SEARCH 6 9 11 12 18 19 20 23 (MODSEQ 20010917162500)
+      S: A143 OK Search complete
+      C: A144 UID SEARCH 1:20
+      S: * SEARCH 6 9 ...
+      S: A144 OK FETCH completed
+
+7.  Security Considerations
+
+   It is believed that this document does not raise any new security
+   concerns that are not already present in the base [IMAP4] protocol,
+   and these issues are discussed in [IMAP4].  Additional security
+   considerations may be found in different extensions mentioned in this
+   document; in particular, in [UIDPLUS], [LITERAL+], [CONDSTORE],
+   [MULTIAPPEND], and [UNSELECT].
+
+   Implementers are also reminded about the importance of thorough
+   testing.
+
+8.  References
+
+8.1.  Normative References
+
+   [KEYWORDS]    Bradner, S., "Key words for use in RFCs to Indicate
+                 Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [IMAP4]       Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+                 VERSION 4rev1", RFC 3501, March 2003.
+
+   [UIDPLUS]     Crispin, M., "Internet Message Access Protocol (IMAP) -
+                 UIDPLUS extension", RFC 4315, December 2005.
+
+   [LITERAL+]    Myers, J., "IMAP4 non-synchronizing literals", RFC
+                 2088, January 1997.
+
+   [CONDSTORE]   Melnikov, A. and S. Hole, "IMAP Extension for
+                 Conditional STORE Operation or Quick Flag Changes
+                 Resynchronization", RFC 4551, June 2006.
+
+   [MULTIAPPEND] Crispin, M., "Internet Message Access Protocol (IMAP) -
+                 MULTIAPPEND Extension", RFC 3502, March 2003.
+
+   [UNSELECT]    Melnikov, A., "Internet Message Access Protocol (IMAP)
+                 UNSELECT command", RFC 3691, February 2004.
+
+   [RFC2683]     Leiba, B., "IMAP4 Implementation Recommendations", RFC
+                 2683, September 1999.
+
+
+
+
+Melnikov                     Informational                     [Page 33]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+8.2.  Informative References
+
+   [ACL]         Melnikov, A., "IMAP4 Access Control List (ACL)
+                 Extension", RFC 4314, December 2005.
+
+   [IMAP-MODEL]  Crispin, M., "Distributed Electronic Mail Models in
+                 IMAP4", RFC 1733, December 1994.
+
+9.  Acknowledgements
+
+   This document is based on version 01 of the text written by Rob
+   Austein in November 1994.
+
+   The editor appreciates comments posted by Mark Crispin to the IMAP
+   mailing list and the comments/corrections/ideas received from Grant
+   Baillie, Cyrus Daboo, John G. Myers, Chris Newman, and Timo Sirainen.
+
+   The editor would also like to thank the developers of Netscape
+   Messenger and Mozilla mail clients for providing examples of
+   disconnected mail clients that served as a base for many
+   recommendations in this document.
+
+Editor's Address
+
+   Alexey Melnikov
+   Isode Limited
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex
+   TW12 2BX
+   United Kingdom
+
+   Phone: +44 77 53759732
+   EMail: alexey.melnikov@isode.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                     Informational                     [Page 34]
+
+RFC 4549        Synch Ops for Disconnected IMAP4 Clients       June 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Melnikov                     Informational                     [Page 35]
+
diff --git a/imap/docs/rfc/rfc4551.txt b/imap/docs/rfc/rfc4551.txt
new file mode 100644
index 00000000..894b5109
--- /dev/null
+++ b/imap/docs/rfc/rfc4551.txt
@@ -0,0 +1,1403 @@
+
+
+
+
+
+
+Network Working Group                                        A. Melnikov
+Request for Comments: 4551                                    Isode Ltd.
+Updates: 3501                                                    S. Hole
+Category: Standards Track                  ACI WorldWide/MessagingDirect
+                                                               June 2006
+
+
+             IMAP Extension for Conditional STORE Operation
+                or Quick Flag Changes Resynchronization
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   Often, multiple IMAP (RFC 3501) clients need to coordinate changes to
+   a common IMAP mailbox.  Examples include different clients working on
+   behalf of the same user, and multiple users accessing shared
+   mailboxes.  These clients need a mechanism to synchronize state
+   changes for messages within the mailbox.  They must be able to
+   guarantee that only one client can change message state (e.g.,
+   message flags) at any time.  An example of such an application is use
+   of an IMAP mailbox as a message queue with multiple dequeueing
+   clients.
+
+   The Conditional Store facility provides a protected update mechanism
+   for message state information that can detect and resolve conflicts
+   between multiple writing mail clients.
+
+   The Conditional Store facility also allows a client to quickly
+   resynchronize mailbox flag changes.
+
+   This document defines an extension to IMAP (RFC 3501).
+
+
+
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                     [Page 1]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+Table of Contents
+
+   1.  Introduction and Overview ................................. 3
+   2.  Conventions Used in This Document ......................... 5
+   3.  IMAP Protocol Changes ..................................... 6
+   3.1. New OK untagged responses for SELECT and EXAMINE ......... 6
+   3.1.1. HIGHESTMODSEQ response code ............................ 6
+   3.1.2. NOMODSEQ response code ................................. 7
+   3.2. STORE and UID STORE Commands ............................. 7
+   3.3 FETCH and UID FETCH Commands ..............................13
+   3.3.1. CHANGEDSINCE FETCH modifier ............................13
+   3.3.2. MODSEQ message data item in FETCH Command ..............14
+   3.4. MODSEQ search criterion in SEARCH ........................16
+   3.5. Modified SEARCH untagged response ........................17
+   3.6. HIGHESTMODSEQ status data items ..........................17
+   3.7. CONDSTORE parameter to SELECT and EXAMINE ................18
+   3.8. Additional quality of implementation issues ..............18
+   4.  Formal Syntax .............................................19
+   5.  Server implementation considerations ......................21
+   6.  Security Considerations ...................................22
+   7.  IANA Considerations .......................................22
+   8.  References ................................................23
+   8.1. Normative References .....................................23
+   8.2. Informative References ...................................23
+   9.  Acknowledgements ..........................................23
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                     [Page 2]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+1. Introduction and Overview
+
+   The Conditional STORE extension is present in any IMAP4
+   implementation that returns "CONDSTORE" as one of the supported
+   capabilities in the CAPABILITY command response.
+
+   An IMAP server that supports this extension MUST associate a positive
+   unsigned 64-bit value called a modification sequence (mod-sequence)
+   with every IMAP message.  This is an opaque value updated by the
+   server whenever a metadata item is modified.  The server MUST
+   guarantee that each STORE command performed on the same mailbox
+   (including simultaneous stores to different metadata items from
+   different connections) will get a different mod-sequence value.
+   Also, for any two successful STORE operations performed in the same
+   session on the same mailbox, the mod-sequence of the second completed
+   operation MUST be greater than the mod-sequence of the first
+   completed.  Note that the latter rule disallows the use of the system
+   clock as a mod-sequence, because if system time changes (e.g., an NTP
+   [NTP] client adjusting the time), the next generated value might be
+   less than the previous one.
+
+   Mod-sequences allow a client that supports the CONDSTORE extension to
+   determine if a message metadata has changed since some known moment.
+   Whenever the state of a flag changes (i.e., the flag is added where
+   previously it wasn't set, or the flag is removed and before it was
+   set) the value of the modification sequence for the message MUST be
+   updated.  Adding the flag when it is already present or removing when
+   it is not present SHOULD NOT change the mod-sequence.
+
+   When a message is appended to a mailbox (via the IMAP APPEND command,
+   COPY to the mailbox, or using an external mechanism) the server
+   generates a new modification sequence that is higher than the highest
+   modification sequence of all messages in the mailbox and assigns it
+   to the appended message.
+
+   The server MAY store separate (per-message) modification sequence
+   values for different metadata items.  If the server does so, per-
+   message mod-sequence is the highest mod-sequence of all metadata
+   items for the specified message.
+
+   The server that supports this extension is not required to be able to
+   store mod-sequences for every available mailbox.  Section 3.1.2
+   describes how the server may act if a particular mailbox doesn't
+   support the persistent storage of mod-sequences.
+
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                     [Page 3]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   This extension makes the following changes to the IMAP4 protocol:
+
+      a) adds UNCHANGEDSINCE STORE modifier.
+
+      b) adds the MODIFIED response code which should be used with an OK
+         response to the STORE command.  (It can also be used in a NO
+         response.)
+
+      c) adds a new MODSEQ message data item for use with the FETCH
+         command.
+
+      d) adds CHANGEDSINCE FETCH modifier.
+
+      e) adds a new MODSEQ search criterion.
+
+      f) extends the syntax of untagged SEARCH responses to include
+         mod-sequence.
+
+      g) adds new OK untagged responses for the SELECT and EXAMINE
+         commands.
+
+      h) defines an additional parameter to SELECT/EXAMINE commands.
+
+      i) adds the HIGHESTMODSEQ status data item to the STATUS command.
+
+   A client supporting CONDSTORE extension indicates its willingness to
+   receive mod-sequence updates in all untagged FETCH responses by
+   issuing:
+
+      -  a SELECT or EXAMINE command with the CONDSTORE parameter,
+      -  a STATUS (HIGHESTMODSEQ) command,
+      -  a FETCH or SEARCH command that includes the MODSEQ message data
+         item,
+      -  a FETCH command with the CHANGEDSINCE modifier, or
+      -  a STORE command with the UNCHANGEDSINCE modifier.
+
+   The server MUST include mod-sequence data in all subsequent untagged
+   FETCH responses (until the connection is closed), whether they were
+   caused by a regular STORE, a STORE with UNCHANGEDSINCE modifier, or
+   an external agent.
+
+   This document uses the term "CONDSTORE-aware client" to refer to a
+   client that announces its willingness to receive mod-sequence updates
+   as described above.  The term "CONDSTORE enabling command" will refer
+   any of the commands listed above.  A future extension to this
+   document may extend the list of CONDSTORE enabling commands.  A first
+   CONDSTORE enabling command executed in the session MUST cause the
+
+
+
+
+Melnikov & Hole             Standards Track                     [Page 4]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   server to return HIGHESTMODSEQ (Section 3.1.1) unless the server has
+   sent NOMODSEQ (Section 3.1.2) response code when the currently
+   selected mailbox was selected.
+
+   The rest of this document describes the protocol changes more
+   rigorously.
+
+2.  Conventions Used in This Document
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+   In examples, lines beginning with "S:" are sent by the IMAP server,
+   and lines beginning with "C:" are sent by the client.  Line breaks
+   may appear in example commands solely for editorial clarity; when
+   present in the actual message, they are represented by "CRLF".
+
+   Formal syntax is defined using ABNF [ABNF].
+
+   The term "metadata" or "metadata item" is used throughout this
+   document.  It refers to any system or user-defined keyword.  Future
+   documents may extend "metadata" to include other dynamic message
+   data.
+
+   Some IMAP mailboxes are private, accessible only to the owning user.
+   Other mailboxes are not, either because the owner has set an Access
+   Control List [ACL] that permits access by other users, or because it
+   is a shared mailbox.  Let's call a metadata item "shared" for the
+   mailbox if any changes to the metadata items are persistent and
+   visible to all other users accessing the mailbox.  Otherwise, the
+   metadata item is called "private".  Note that private metadata items
+   are still visible to all sessions accessing the mailbox as the same
+   user.  Also note that different mailboxes may have different metadata
+   items as shared.
+
+   See Section 1 for the definition of a "CONDSTORE-aware client" and a
+   "CONDSTORE enabling command".
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                     [Page 5]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+3.  IMAP Protocol Changes
+
+3.1.  New OK Untagged Responses for SELECT and EXAMINE
+
+   This document adds two new response codes, HIGHESTMODSEQ and
+   NOMODSEQ.  One of those response codes MUST be returned in the OK
+   untagged response for a successful SELECT/EXAMINE command.
+
+   When opening a mailbox, the server must check if the mailbox supports
+   the persistent storage of mod-sequences.  If the mailbox supports the
+   persistent storage of mod-sequences and the mailbox open operation
+   succeeds, the server MUST send the OK untagged response including
+   HIGHESTMODSEQ response code.  If the persistent storage for the
+   mailbox is not supported, the server MUST send the OK untagged
+   response including NOMODSEQ response code instead.
+
+3.1.1.  HIGHESTMODSEQ Response Code
+
+   This document adds a new response code that is returned in the OK
+   untagged response for the SELECT and EXAMINE commands.  A server
+   supporting the persistent storage of mod-sequences for the mailbox
+   MUST send the OK untagged response including HIGHESTMODSEQ response
+   code with every successful SELECT or EXAMINE command:
+
+      OK [HIGHESTMODSEQ <mod-sequence-value>]
+
+      where <mod-sequence-value> is the highest mod-sequence value of
+      all messages in the mailbox.  When the server changes UIDVALIDITY
+      for a mailbox, it doesn't have to keep the same HIGHESTMODSEQ for
+      the mailbox.
+
+   A disconnected client can use the value of HIGHESTMODSEQ to check if
+   it has to refetch metadata from the server.  If the UIDVALIDITY value
+   has changed for the selected mailbox, the client MUST delete the
+   cached value of HIGHESTMODSEQ.  If UIDVALIDITY for the mailbox is the
+   same, and if the HIGHESTMODSEQ value stored in the client's cache is
+   less than the value returned by the server, then some metadata items
+   on the server have changed since the last synchronization, and the
+   client needs to update its cache.  The client MAY use SEARCH MODSEQ
+   (Section 3.4) to find out exactly which metadata items have changed.
+   Alternatively, the client MAY issue FETCH with the CHANGEDSINCE
+   modifier (Section 3.3.1) in order to fetch data for all messages that
+   have metadata items changed since some known modification sequence.
+
+   Example 1:
+
+      C: A142 SELECT INBOX
+      S: * 172 EXISTS
+
+
+
+Melnikov & Hole             Standards Track                     [Page 6]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+      S: * 1 RECENT
+      S: * OK [UNSEEN 12] Message 12 is first unseen
+      S: * OK [UIDVALIDITY 3857529045] UIDs valid
+      S: * OK [UIDNEXT 4392] Predicted next UID
+      S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+      S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+      S: * OK [HIGHESTMODSEQ 715194045007]
+      S: A142 OK [READ-WRITE] SELECT completed
+
+3.1.2.  NOMODSEQ Response Code
+
+   A server that doesn't support the persistent storage of mod-sequences
+   for the mailbox MUST send the OK untagged response including NOMODSEQ
+   response code with every successful SELECT or EXAMINE command.  A
+   server that returned NOMODSEQ response code for a mailbox, which
+   subsequently receives one of the following commands while the mailbox
+   is selected:
+
+      -  a FETCH command with the CHANGEDSINCE modifier,
+      -  a FETCH or SEARCH command that includes the MODSEQ message data
+         item, or
+      -  a STORE command with the UNCHANGEDSINCE modifier
+
+   MUST reject any such command with the tagged BAD response.
+
+   Example 2:
+
+      C: A142 SELECT INBOX
+      S: * 172 EXISTS
+      S: * 1 RECENT
+      S: * OK [UNSEEN 12] Message 12 is first unseen
+      S: * OK [UIDVALIDITY 3857529045] UIDs valid
+      S: * OK [UIDNEXT 4392] Predicted next UID
+      S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+      S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+      S: * OK [NOMODSEQ] Sorry, this mailbox format doesn't support
+           modsequences
+      S: A142 OK [READ-WRITE] SELECT completed
+
+3.2.  STORE and UID STORE Commands
+
+   This document defines the following STORE modifier (see Section 2.5
+   of [IMAPABNF]):
+
+   UNCHANGEDSINCE <mod-sequence>
+
+      For each message specified in the message set, the server performs
+      the following.  If the mod-sequence of any metadata item of the
+
+
+
+Melnikov & Hole             Standards Track                     [Page 7]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+      message is equal or less than the specified UNCHANGEDSINCE value,
+      then the requested operation (as described by the message data
+      item) is performed.  If the operation is successful, the server
+      MUST update the mod-sequence attribute of the message.  An
+      untagged FETCH response MUST be sent, even if the .SILENT suffix
+      is specified, and the response MUST include the MODSEQ message
+      data item.  This is required to update the client's cache with the
+      correct mod-sequence values.  See Section 3.3.2 for more details.
+
+      However, if the mod-sequence of any metadata item of the message
+      is greater than the specified UNCHANGEDSINCE value, then the
+      requested operation MUST NOT be performed.  In this case, the
+      mod-sequence attribute of the message is not updated, and the
+      message number (or unique identifier in the case of the UID STORE
+      command) is added to the list of messages that failed the
+      UNCHANGESINCE test.
+
+      When the server finished performing the operation on all the
+      messages in the message set, it checks for a non-empty list of
+      messages that failed the UNCHANGESINCE test.  If this list is
+      non-empty, the server MUST return in the tagged response a
+      MODIFIED response code.  The MODIFIED response code includes the
+      message set (for STORE) or set of UIDs (for UID STORE) of all
+      messages that failed the UNCHANGESINCE test.
+
+   Example 3:
+
+      All messages pass the UNCHANGESINCE test.
+
+      C: a103 UID STORE 6,4,8 (UNCHANGEDSINCE 12121230045)
+          +FLAGS.SILENT (\Deleted)
+      S: * 1 FETCH (UID 4 MODSEQ (12121231000))
+      S: * 2 FETCH (UID 6 MODSEQ (12121230852))
+      S: * 4 FETCH (UID 8 MODSEQ (12121130956))
+      S: a103 OK Conditional Store completed
+
+   Example 4:
+
+      C: a104 STORE * (UNCHANGEDSINCE 12121230045) +FLAGS.SILENT
+         (\Deleted $Processed)
+      S: * 50 FETCH (MODSEQ (12111230047))
+      S: a104 OK Store (conditional) completed
+
+   Example 5:
+
+      C: c101 STORE 1 (UNCHANGEDSINCE 12121230045) -FLAGS.SILENT
+         (\Deleted)
+      S: * OK [HIGHESTMODSEQ 12111230047]
+
+
+
+Melnikov & Hole             Standards Track                     [Page 8]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+      S: * 50 FETCH (MODSEQ (12111230048))
+      S: c101 OK Store (conditional) completed
+
+      HIGHESTMODSEQ response code was sent by the server presumably
+      because this was the first CONDSTORE enabling command.
+
+   Example 6:
+
+      In spite of the failure of the conditional STORE operation for
+      message 7, the server continues to process the conditional STORE
+      in order to find all messages that fail the test.
+
+      C: d105 STORE 7,5,9 (UNCHANGEDSINCE 320162338)
+          +FLAGS.SILENT (\Deleted)
+      S: * 5 FETCH (MODSEQ (320162350))
+      S: d105 OK [MODIFIED 7,9] Conditional STORE failed
+
+   Example 7:
+
+      Same as above, but the server follows the SHOULD recommendation in
+      Section 6.4.6 of [IMAP4].
+
+      C: d105 STORE 7,5,9 (UNCHANGEDSINCE 320162338)
+          +FLAGS.SILENT (\Deleted)
+      S: * 7 FETCH (MODSEQ (320162342) FLAGS (\Seen \Deleted))
+      S: * 5 FETCH (MODSEQ (320162350))
+      S: * 9 FETCH (MODSEQ (320162349) FLAGS (\Answered))
+      S: d105 OK [MODIFIED 7,9] Conditional STORE failed
+
+      Use of UNCHANGEDSINCE with a modification sequence of 0 always
+      fails if the metadata item exists.  A system flag MUST always be
+      considered existent, whether it was set or not.
+
+   Example 8:
+
+      C: a102 STORE 12 (UNCHANGEDSINCE 0)
+          +FLAGS.SILENT ($MDNSent)
+      S: a102 OK [MODIFIED 12] Conditional STORE failed
+
+      The client has tested the presence of the $MDNSent user-defined
+      keyword.
+
+   Note: A client trying to make an atomic change to the state of a
+   particular metadata item (or a set of metadata items) should be
+   prepared to deal with the case when the server returns the MODIFIED
+   response code if the state of the metadata item being watched hasn't
+   changed (but the state of some other metadata item has).  This is
+   necessary, because some servers don't store separate mod-sequences
+
+
+
+Melnikov & Hole             Standards Track                     [Page 9]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   for different metadata items.  However, a server implementation
+   SHOULD avoid generating spurious MODIFIED responses for +FLAGS/-FLAGS
+   STORE operations, even when the server stores a single mod-sequence
+   per message.  Section 5 describes how this can be achieved.
+
+   Unless the server has included an unsolicited FETCH to update
+   client's knowledge about messages that have failed the UNCHANGEDSINCE
+   test, upon receipt of the MODIFIED response code, the client SHOULD
+   try to figure out if the required metadata items have indeed changed
+   by issuing FETCH or NOOP command.  It is RECOMMENDED that the server
+   avoids the need for the client to do that by sending an unsolicited
+   FETCH response (Examples 9 and 10).
+
+   If the required metadata items haven't changed, the client SHOULD
+   retry the command with the new mod-sequence.  The client SHOULD allow
+   for a configurable but reasonable number of retries (at least 2).
+
+   Example 9:
+
+      In the example below, the server returns the MODIFIED response
+      code without sending information describing why the STORE
+      UNCHANGEDSINCE operation has failed.
+
+      C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+          +FLAGS.SILENT ($Processed)
+      S: * 100 FETCH (MODSEQ (303181230852))
+      S: * 102 FETCH (MODSEQ (303181230852))
+      ...
+      S: * 150 FETCH (MODSEQ (303181230852))
+      S: a106 OK [MODIFIED 101] Conditional STORE failed
+
+      The flag $Processed was set on the message 101...
+
+      C: a107 NOOP
+      S: * 101 FETCH (MODSEQ (303011130956) FLAGS ($Processed))
+      S: a107 OK
+
+      Or the flag hasn't changed, but another has (note that this server
+      behaviour is discouraged.  Server implementers should also see
+      Section 5)...
+
+      C: b107 NOOP
+      S: * 101 FETCH (MODSEQ (303011130956) FLAGS (\Deleted \Answered))
+      S: b107 OK
+
+      ...and the client retries the operation for the message 101 with
+      the updated UNCHANGEDSINCE value
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 10]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+      C: b108 STORE 101 (UNCHANGEDSINCE 303011130956)
+          +FLAGS.SILENT ($Processed)
+      S: * 101 FETCH (MODSEQ (303181230852))
+      S: b108 OK Conditional Store completed
+
+   Example 10:
+
+      Same as above, but the server avoids the need for the client to
+      poll for changes.
+
+      The flag $Processed was set on the message 101 by another
+      client...
+
+      C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+          +FLAGS.SILENT ($Processed)
+      S: * 100 FETCH (MODSEQ (303181230852))
+      S: * 101 FETCH (MODSEQ (303011130956) FLAGS ($Processed))
+      S: * 102 FETCH (MODSEQ (303181230852))
+      ...
+      S: * 150 FETCH (MODSEQ (303181230852))
+      S: a106 OK [MODIFIED 101] Conditional STORE failed
+
+      Or the flag hasn't changed, but another has (note that this server
+      behaviour is discouraged.  Server implementers should also see
+      Section 5)...
+
+      C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+          +FLAGS.SILENT ($Processed)
+      S: * 100 FETCH (MODSEQ (303181230852))
+      S: * 101 FETCH (MODSEQ (303011130956) FLAGS (\Deleted \Answered))
+      S: * 102 FETCH (MODSEQ (303181230852))
+      ...
+      S: * 150 FETCH (MODSEQ (303181230852))
+      S: a106 OK [MODIFIED 101] Conditional STORE failed
+
+      ...and the client retries the operation for the message 101 with
+      the updated UNCHANGEDSINCE value
+
+      C: b108 STORE 101 (UNCHANGEDSINCE 303011130956)
+          +FLAGS.SILENT ($Processed)
+      S: * 101 FETCH (MODSEQ (303181230852))
+      S: b108 OK Conditional Store completed
+
+      Or the flag hasn't changed, but another has (nice server
+      behaviour.  Server implementers should also see Section 5)...
+
+      C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+          +FLAGS.SILENT ($Processed)
+
+
+
+Melnikov & Hole             Standards Track                    [Page 11]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+      S: * 100 FETCH (MODSEQ (303181230852))
+      S: * 101 FETCH (MODSEQ (303011130956) FLAGS ($Processed \Deleted
+           \Answered))
+      S: * 102 FETCH (MODSEQ (303181230852))
+      ...
+      S: * 150 FETCH (MODSEQ (303181230852))
+      S: a106 OK Conditional STORE completed
+
+   Example 11:
+
+      The following example is based on the example from the Section
+      4.2.3 of [RFC-2180] and demonstrates that the MODIFIED response
+      code may be also returned in the tagged NO response.
+
+      Client tries to conditionally STORE flags on a mixture of expunged
+      and non-expunged messages; one message fails the UNCHANGEDSINCE
+      test.
+
+      C: B001 STORE 1:7 (UNCHANGEDSINCE 320172338) +FLAGS (\SEEN)
+      S: * 1 FETCH (MODSEQ (320172342) FLAGS (\SEEN))
+      S: * 3 FETCH (MODSEQ (320172342) FLAGS (\SEEN))
+      S: B001 NO [MODIFIED 2] Some of the messages no longer exist.
+
+      C: B002 NOOP
+      S: * 4 EXPUNGE
+      S: * 4 EXPUNGE
+      S: * 4 EXPUNGE
+      S: * 4 EXPUNGE
+      S: * 2 FETCH (MODSEQ (320172340) FLAGS (\Deleted \Answered))
+      S: B002 OK NOOP Completed.
+
+      By receiving FETCH responses for messages 1 and 3, and EXPUNGE
+      responses that indicate that messages 4 through 7 have been
+      expunged, the client retries the operation only for the message 2.
+      The updated UNCHANGEDSINCE value is used.
+
+      C: b003 STORE 2 (UNCHANGEDSINCE 320172340) +FLAGS (\Seen)
+      S: * 2 FETCH (MODSEQ (320180050))
+      S: b003 OK Conditional Store completed
+
+   Note: If a message is specified multiple times in the message set,
+   and the server doesn't internally eliminate duplicates from the
+   message set, it MUST NOT fail the conditional STORE operation for the
+   second (or subsequent) occurrence of the message if the operation
+   completed successfully for the first occurrence.  For example, if the
+   client specifies:
+
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 12]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+         e105 STORE 7,3:9 (UNCHANGEDSINCE 12121230045)
+          +FLAGS.SILENT (\Deleted)
+
+   the server must not fail the operation for message 7 as part of
+   processing "3:9" if it succeeded when message 7 was processed the
+   first time.
+
+   Once the client specified the UNCHANGEDSINCE modifier in a STORE
+   command, the server MUST include the MODSEQ fetch response data items
+   in all subsequent unsolicited FETCH responses.
+
+   This document also changes the behaviour of the server when it has
+   performed a STORE or UID STORE command and the UNCHANGEDSINCE
+   modifier is not specified.  If the operation is successful for a
+   message, the server MUST update the mod-sequence attribute of the
+   message.  The server is REQUIRED to include the mod-sequence value
+   whenever it decides to send the unsolicited FETCH response to all
+   CONDSTORE-aware clients that have opened the mailbox containing the
+   message.
+
+   Server implementers should also see Section 3.8 for additional
+   quality of implementation issues related to the STORE command.
+
+3.3.  FETCH and UID FETCH Commands
+
+3.3.1.  CHANGEDSINCE FETCH Modifier
+
+   This document defines the following FETCH modifier (see Section 2.4
+   of [IMAPABNF]):
+
+   CHANGEDSINCE <mod-sequence>
+
+      CHANGEDSINCE FETCH modifier allows to create a further subset of
+      the list of messages described by sequence set.  The information
+      described by message data items is only returned for messages that
+      have mod-sequence bigger than <mod-sequence>.
+
+      When CHANGEDSINCE FETCH modifier is specified, it implicitly adds
+      MODSEQ FETCH message data item (Section 3.3.2).
+
+   Example 12:
+
+      C: s100 UID FETCH 1:* (FLAGS) (CHANGEDSINCE 12345)
+      S: * 1 FETCH (UID 4 MODSEQ (65402) FLAGS (\Seen))
+      S: * 2 FETCH (UID 6 MODSEQ (75403) FLAGS (\Deleted))
+      S: * 4 FETCH (UID 8 MODSEQ (29738) FLAGS ($NoJunk $AutoJunk
+           $MDNSent))
+      S: s100 OK FETCH completed
+
+
+
+Melnikov & Hole             Standards Track                    [Page 13]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+3.3.2.  MODSEQ Message Data Item in FETCH Command
+
+   This extension adds a MODSEQ message data item to the FETCH command.
+   The MODSEQ message data item allows clients to retrieve mod-sequence
+   values for a range of messages in the currently selected mailbox.
+
+   Once the client specified the MODSEQ message data item in a FETCH
+   request, the server MUST include the MODSEQ fetch response data items
+   in all subsequent unsolicited FETCH responses.
+
+   Syntax:  MODSEQ
+
+      The MODSEQ message data item causes the server to return MODSEQ
+      fetch response data items.
+
+   Syntax:  MODSEQ ( <permsg-modsequence> )
+
+      MODSEQ response data items contain per-message mod-sequences.
+
+      The MODSEQ response data item is returned if the client issued
+      FETCH with MODSEQ message data item.  It also allows the server to
+      notify the client about mod-sequence changes caused by conditional
+      STOREs (Section 3.2) and/or changes caused by external sources.
+
+   Example 13:
+
+      C: a FETCH 1:3 (MODSEQ)
+      S: * 1 FETCH (MODSEQ (624140003))
+      S: * 2 FETCH (MODSEQ (624140007))
+      S: * 3 FETCH (MODSEQ (624140005))
+      S: a OK Fetch complete
+
+      In this example, the client requests per-message mod-sequences for
+      a set of messages.
+
+   When a flag for a message is modified in a different session, the
+   server sends an unsolicited FETCH response containing the mod-
+   sequence for the message.
+
+   Example 14:
+
+      (Session 1, authenticated as a user "alex").  The user adds a
+      shared flag \Deleted:
+
+         C: A142 SELECT INBOX
+         ...
+         S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+         S: * OK [PERMANENTFLAGS (\Answered \Deleted \Seen \*)] Limited
+
+
+
+Melnikov & Hole             Standards Track                    [Page 14]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+         ...
+
+         C: A160 STORE 7 +FLAGS.SILENT (\Deleted)
+         S: * 7 FETCH (MODSEQ (2121231000))
+         S: A160 OK Store completed
+
+      (Session 2, also authenticated as the user "alex").  Any changes
+      to flags are always reported to all sessions authenticated as the
+      same user as in the session 1.
+
+         C: C180 NOOP
+         S: * 7 FETCH (FLAGS (\Deleted \Answered) MODSEQ (12121231000))
+         S: C180 OK Noop completed
+
+      (Session 3, authenticated as a user "andrew").  As \Deleted is a
+      shared flag, changes in session 1 are also reported in session 3:
+
+         C: D210 NOOP
+         S: * 7 FETCH (FLAGS (\Deleted \Answered) MODSEQ (12121231000))
+         S: D210 OK Noop completed
+
+      The user modifies a private flag \Seen in session 1...
+
+         C: A240 STORE 7 +FLAGS.SILENT (\Seen)
+         S: * 7 FETCH (MODSEQ (12121231777))
+         S: A240 OK Store completed
+
+      ...which is only reported in session 2...
+
+         C: C270 NOOP
+         S: * 7 FETCH (FLAGS (\Deleted \Answered \Seen) MODSEQ
+              (12121231777))
+         S: C270 OK Noop completed
+
+      ...but not in session 3.
+
+         C: D300 NOOP
+         S: D300 OK Noop completed
+
+      And finally, the user removes flags \Answered (shared) and \Seen
+      (private) in session 1.
+
+         C: A330 STORE 7 -FLAGS.SILENT (\Answered \Seen)
+         S: * 7 FETCH (MODSEQ (12121245160))
+         S: A330 OK Store completed
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 15]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+      Both changes are reported in the session 2...
+
+         C: C360 NOOP
+         S: * 7 FETCH (FLAGS (\Deleted) MODSEQ (12121245160))
+         S: C360 OK Noop completed
+
+      ...and only changes to shared flags are reported in session 3.
+
+         C: D390 NOOP
+         S: * 7 FETCH (FLAGS (\Deleted) MODSEQ (12121245160))
+         S: D390 OK Noop completed
+
+   Server implementers should also see Section 3.8 for additional
+   quality of implementation issues related to the FETCH command.
+
+3.4.  MODSEQ Search Criterion in SEARCH
+
+   The MODSEQ criterion for the SEARCH command allows a client to search
+   for the metadata items that were modified since a specified moment.
+
+   Syntax:  MODSEQ [<entry-name> <entry-type-req>] <mod-sequence-valzer>
+
+      Messages that have modification values that are equal to or
+      greater than <mod-sequence-valzer>.  This allows a client, for
+      example, to find out which messages contain metadata items that
+      have changed since the last time it updated its disconnected
+      cache.  The client may also specify <entry-name> (name of metadata
+      item) and <entry-type-req> (type of metadata item) before
+      <mod-sequence-valzer>.  <entry-type-req> can be one of "shared",
+      "priv" (private), or "all".  The latter means that the server
+      should use the biggest value among "priv" and "shared" mod-
+      sequences for the metadata item.  If the server doesn't store
+      internally separate mod-sequences for different metadata items, it
+      MUST ignore <entry-name> and <entry-type-req>.  Otherwise, the
+      server should use them to narrow down the search.
+
+      For a flag <flagname>, the corresponding <entry-name> has a form
+      "/flags/<flagname>" as defined in [IMAPABNF].  Note that the
+      leading "\" character that denotes a system flag has to be escaped
+      as per Section 4.3 of [IMAP4], as the <entry-name> uses syntax for
+      quoted strings.
+
+   If client specifies a MODSEQ criterion in a SEARCH command and the
+   server returns a non-empty SEARCH result, the server MUST also append
+   (to the end of the untagged SEARCH response) the highest mod-sequence
+   for all messages being returned.  See also Section 3.5.
+
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 16]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   Example 15:
+
+      C: a SEARCH MODSEQ "/flags/\\draft" all 620162338
+      S: * SEARCH 2 5 6 7 11 12 18 19 20 23 (MODSEQ 917162500)
+      S: a OK Search complete
+
+      In the above example, the message numbers of any messages
+      containing the string "IMAP4" in the "value" attribute of the
+      "/comment" entry and having a mod-sequence equal to or greater
+      than 620162338 for the "\Draft" flag are returned in the search
+      results.
+
+   Example 16:
+
+      C: t SEARCH OR NOT MODSEQ 720162338 LARGER 50000
+      S: * SEARCH
+      S: t OK Search complete, nothing found
+
+3.5.  Modified SEARCH Untagged Response
+
+   Data:       zero or more numbers
+               mod-sequence value (omitted if no match)
+
+   This document extends syntax of the untagged SEARCH response to
+   include the highest mod-sequence for all messages being returned.
+
+   If a client specifies a MODSEQ criterion in a SEARCH (or UID SEARCH)
+   command and the server returns a non-empty SEARCH result, the server
+   MUST also append (to the end of the untagged SEARCH response) the
+   highest mod-sequence for all messages being returned.  See Section
+   3.4 for examples.
+
+3.6.  HIGHESTMODSEQ Status Data Items
+
+   This document defines a new status data item:
+
+   HIGHESTMODSEQ
+
+      The highest mod-sequence value of all messages in the mailbox.
+      This is the same value that is returned by the server in the
+      HIGHESTMODSEQ response code in an OK untagged response (see
+      Section 3.1.1).  If the server doesn't support the persistent
+      storage of mod-sequences for the mailbox (see Section 3.1.2), the
+      server MUST return 0 as the value of HIGHESTMODSEQ status data
+      item.
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 17]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   Example 17:
+
+      C: A042 STATUS blurdybloop (UIDNEXT MESSAGES HIGHESTMODSEQ)
+      S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292
+           HIGHESTMODSEQ 7011231777)
+      S: A042 OK STATUS completed
+
+3.7.  CONDSTORE Parameter to SELECT and EXAMINE
+
+   The CONDSTORE extension defines a single optional select parameter,
+   "CONDSTORE", which tells the server that it MUST include the MODSEQ
+   fetch response data items in all subsequent unsolicited FETCH
+   responses.
+
+   The CONDSTORE parameter to SELECT/EXAMINE helps avoid a race
+   condition that might arise when one or more metadata items are
+   modified in another session after the server has sent the
+   HIGHESTMODSEQ response code and before the client was able to issue a
+   CONDSTORE enabling command.
+
+   Example 18:
+
+      C: A142 SELECT INBOX (CONDSTORE)
+      S: * 172 EXISTS
+      S: * 1 RECENT
+      S: * OK [UNSEEN 12] Message 12 is first unseen
+      S: * OK [UIDVALIDITY 3857529045] UIDs valid
+      S: * OK [UIDNEXT 4392] Predicted next UID
+      S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+      S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+      S: * OK [HIGHESTMODSEQ 715194045007]
+      S: A142 OK [READ-WRITE] SELECT completed, CONDSTORE is now enabled
+
+3.8.  Additional Quality-of-Implementation Issues
+
+   Server implementations should follow the following rule, which
+   applies to any successfully completed STORE/UID STORE (with and
+   without UNCHANGEDSINCE modifier), as well as to a FETCH command that
+   implicitly sets \Seen flag:
+
+      Adding the flag when it is already present or removing when it is
+      not present SHOULD NOT change the mod-sequence.
+
+   This will prevent spurious client synchronization requests.
+
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 18]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   However, note that client implementers MUST NOT rely on this server
+   behavior.  A client can't distinguish between the case when a server
+   has violated the SHOULD mentioned above, and that when one or more
+   clients set and unset (or unset and set) the flag in another session.
+
+4.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) [ABNF] notation.  Elements not defined here can be found
+   in the formal syntax of the ABNF [ABNF], IMAP [IMAP4], and IMAP ABNF
+   extensions [IMAPABNF] specifications.
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper- or lowercase characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+   capability          =/ "CONDSTORE"
+
+   status-att          =/ "HIGHESTMODSEQ"
+                          ;; extends non-terminal defined in RFC 3501.
+
+   status-att-val      =/ "HIGHESTMODSEQ" SP mod-sequence-valzer
+                          ;; extends non-terminal defined in [IMAPABNF].
+                          ;; Value 0 denotes that the mailbox doesn't
+                          ;; support persistent mod-sequences
+                          ;; as described in Section 3.1.2
+
+   store-modifier      =/ "UNCHANGEDSINCE" SP mod-sequence-valzer
+                          ;; Only a single "UNCHANGEDSINCE" may be
+                          ;; specified in a STORE operation
+
+   fetch-modifier      =/ chgsince-fetch-mod
+                          ;; conforms to the generic "fetch-modifier"
+                          ;; syntax defined in [IMAPABNF].
+
+   chgsince-fetch-mod  = "CHANGEDSINCE" SP mod-sequence-value
+                          ;; CHANGEDSINCE FETCH modifier conforms to
+                          ;; the fetch-modifier syntax
+
+   fetch-att           =/ fetch-mod-sequence
+                          ;; modifies original IMAP4 fetch-att
+
+   fetch-mod-sequence  = "MODSEQ"
+
+   fetch-mod-resp      = "MODSEQ" SP "(" permsg-modsequence ")"
+
+   msg-att-dynamic     =/ fetch-mod-resp
+
+
+
+Melnikov & Hole             Standards Track                    [Page 19]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   search-key          =/ search-modsequence
+                          ;; modifies original IMAP4 search-key
+                          ;;
+                          ;; This change applies to all commands
+                          ;; referencing this non-terminal, in
+                          ;; particular SEARCH.
+
+   search-modsequence  = "MODSEQ" [search-modseq-ext] SP
+                         mod-sequence-valzer
+
+   search-modseq-ext   = SP entry-name SP entry-type-req
+
+   resp-text-code      =/ "HIGHESTMODSEQ" SP mod-sequence-value /
+                          "NOMODSEQ" /
+                          "MODIFIED" SP set
+
+   entry-name          = entry-flag-name
+
+   entry-flag-name     = DQUOTE "/flags/" attr-flag DQUOTE
+                          ;; each system or user defined flag <flag>
+                          ;; is mapped to "/flags/<flag>".
+                          ;;
+                          ;; <entry-flag-name> follows the escape rules
+                          ;; used by "quoted" string as described in
+                          ;; Section 4.3 of [IMAP4], e.g., for the flag
+                          ;; \Seen the corresponding <entry-name> is
+                          ;; "/flags/\\seen", and for the flag
+                          ;; $MDNSent, the corresponding <entry-name>
+                          ;; is "/flags/$mdnsent".
+
+   entry-type-resp     = "priv" / "shared"
+                          ;; metadata item type
+
+   entry-type-req      = entry-type-resp / "all"
+                          ;; perform SEARCH operation on private
+                          ;; metadata item, shared metadata item or both
+
+   permsg-modsequence  = mod-sequence-value
+                          ;; per message mod-sequence
+
+   mod-sequence-value  = 1*DIGIT
+                          ;; Positive unsigned 64-bit integer
+                          ;; (mod-sequence)
+                          ;; (1 <= n < 18,446,744,073,709,551,615)
+
+   mod-sequence-valzer = "0" / mod-sequence-value
+
+   search-sort-mod-seq = "(" "MODSEQ" SP mod-sequence-value ")"
+
+
+
+Melnikov & Hole             Standards Track                    [Page 20]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   select-param        =/ condstore-param
+                          ;; conforms to the generic "select-param"
+                          ;; non-terminal syntax defined in [IMAPABNF].
+
+   condstore-param     = "CONDSTORE"
+
+   mailbox-data        =/ "SEARCH" [1*(SP nz-number) SP
+                          search-sort-mod-seq]
+
+   attr-flag           = "\\Answered" / "\\Flagged" / "\\Deleted" /
+                         "\\Seen" / "\\Draft" / attr-flag-keyword /
+                         attr-flag-extension
+                          ;; Does not include "\\Recent"
+
+   attr-flag-extension = "\\" atom
+                          ;; Future expansion.  Client implementations
+                          ;; MUST accept flag-extension flags.  Server
+                          ;; implementations MUST NOT generate
+                          ;; flag-extension flags except as defined by
+                          ;; future standard or standards-track
+                          ;; revisions of [IMAP4].
+
+   attr-flag-keyword   = atom
+
+5.  Server Implementation Considerations
+
+   This section describes how a server implementation that doesn't store
+   separate per-metadata mod-sequences for different metadata items can
+   avoid sending the MODIFIED response to any of the following
+   conditional STORE operations:
+
+      +FLAGS
+      -FLAGS
+      +FLAGS.SILENT
+      -FLAGS.SILENT
+
+   Note that the optimization described in this section can't be
+   performed in case of a conditional STORE FLAGS operation.
+
+   Let's use the following example.  The client has issued
+
+      C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+         +FLAGS.SILENT ($Processed)
+
+   When the server receives the command and parses it successfully, it
+   iterates through the message set and tries to execute the conditional
+   STORE command for each message.
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 21]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+   Each server internally works as a client, i.e., it has to cache the
+   current state of all IMAP flags as it is known to the client.  In
+   order to report flag changes to the client, the server compares the
+   cached values with the values in its database for IMAP flags.
+
+   Imagine that another client has changed the state of a flag \Deleted
+   on the message 101 and that the change updated the mod-sequence for
+   the message.  The server knows that the mod-sequence for the mailbox
+   has changed; however, it also knows that:
+
+   a) the client is not interested in \Deleted flag, as it hasn't
+      included it in +FLAGS.SILENT operation; and
+
+   b) the state of the flag $Processed hasn't changed (the server can
+      determine this by comparing cached flag state with the state of
+      the flag in the database).
+
+   Therefore, the server doesn't have to report MODIFIED to the client.
+   Instead, the server may set $Processed flag, update the mod-sequence
+   for the message 101 once again and send an untagged FETCH response
+   with new mod-sequence and flags:
+
+      S: * 101 FETCH (MODSEQ (303011130956)
+         FLAGS ($Processed \Deleted \Answered))
+
+   See also Section 3.8 for additional quality-of-implementation issues.
+
+6.  Security Considerations
+
+   It is believed that the Conditional STORE extension doesn't raise any
+   new security concerns that are not already discussed in [IMAP4].
+   However, the availability of this extension may make it possible for
+   IMAP4 to be used in critical applications it could not be used for
+   previously, making correct IMAP server implementation and operation
+   even more important.
+
+7.  IANA Considerations
+
+   IMAP4 capabilities are registered by publishing a standards track or
+   IESG approved experimental RFC.  The registry is currently located
+   at:
+
+         http://www.iana.org/assignments/imap4-capabilities
+
+   This document defines the CONDSTORE IMAP capability.  IANA has added
+   it to the registry accordingly.
+
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 22]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+8.  References
+
+8.1.  Normative References
+
+   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [ABNF]     Crocker, D. and P. Overell, "Augmented BNF for Syntax
+              Specifications: ABNF", RFC 4234, October 2005.
+
+   [IMAP4]    Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+              4rev1", RFC 3501, March 2003.
+
+   [IMAPABNF] Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
+              ABNF", RFC 4466, April 2006.
+
+8.2.  Informative References
+
+   [ACAP]     Newman, C. and J. Myers, "ACAP -- Application
+              Configuration Access Protocol", RFC 2244, November 1997.
+
+   [ACL]      Melnikov, A., "IMAP4 Access Control List (ACL) Extension",
+              RFC 4314, December 2005.
+
+   [ANN]      Daboo, C. and R. Gellens, "IMAP ANNOTATE Extension", Work
+              in Progress, March 2006.
+
+   [NTP]      Mills, D., "Network Time Protocol (Version 3)
+              Specification, Implementation and Analysis", RFC 1305,
+              March 1992.
+
+   [RFC-2180] Gahrns, M., "IMAP4 Multi-Accessed Mailbox Practice", RFC
+              2180, July 1997.
+
+9.  Acknowledgements
+
+   Some text was borrowed from "IMAP ANNOTATE Extension" [ANN] by
+   Randall Gellens and Cyrus Daboo and from "ACAP -- Application
+   Configuration Access Protocol" [ACAP] by Chris Newman and John Myers.
+
+   Many thanks to Randall Gellens for his thorough review of the
+   document.
+
+   The authors also acknowledge the feedback provided by Cyrus Daboo,
+   Larry Greenfield, Chris Newman, Harrie Hazewinkel, Arnt Gulbrandsen,
+   Timo Sirainen, Mark Crispin, Ned Freed, Ken Murchison, and Dave
+   Cridland.
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 23]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+Authors' Addresses
+
+   Alexey Melnikov
+   Isode Limited
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex
+   TW12 2BX,
+   United Kingdom
+
+   EMail: Alexey.Melnikov@isode.com
+
+
+   Steve Hole
+   ACI WorldWide/MessagingDirect
+   #1807, 10088 102 Ave
+   Edmonton, AB
+   T5J 2Z1
+   Canada
+
+   EMail: Steve.Hole@messagingdirect.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 24]
+
+RFC 4551          IMAP Extension for Conditional STORE         June 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Melnikov & Hole             Standards Track                    [Page 25]
+
diff --git a/imap/docs/rfc/rfc4616.txt b/imap/docs/rfc/rfc4616.txt
new file mode 100644
index 00000000..991189d5
--- /dev/null
+++ b/imap/docs/rfc/rfc4616.txt
@@ -0,0 +1,619 @@
+
+
+
+
+
+
+Network Working Group                                   K. Zeilenga, Ed.
+Request for Comments: 4616                           OpenLDAP Foundation
+Updates: 2595                                                August 2006
+Category: Standards Track
+
+
+  The PLAIN Simple Authentication and Security Layer (SASL) Mechanism
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2006).
+
+Abstract
+
+   This document defines a simple clear-text user/password Simple
+   Authentication and Security Layer (SASL) mechanism called the PLAIN
+   mechanism.  The PLAIN mechanism is intended to be used, in
+   combination with data confidentiality services provided by a lower
+   layer, in protocols that lack a simple password authentication
+   command.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 1]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+1.  Introduction
+
+   Clear-text, multiple-use passwords are simple, interoperate with
+   almost all existing operating system authentication databases, and
+   are useful for a smooth transition to a more secure password-based
+   authentication mechanism.  The drawback is that they are unacceptable
+   for use over network connections where data confidentiality is not
+   ensured.
+
+   This document defines the PLAIN Simple Authentication and Security
+   Layer ([SASL]) mechanism for use in protocols with no clear-text
+   login command (e.g., [ACAP] or [SMTP-AUTH]).  This document updates
+   RFC 2595, replacing Section 6.  Changes since RFC 2595 are detailed
+   in Appendix A.
+
+   The name associated with this mechanism is "PLAIN".
+
+   The PLAIN SASL mechanism does not provide a security layer.
+
+   The PLAIN mechanism should not be used without adequate data security
+   protection as this mechanism affords no integrity or confidentiality
+   protections itself.  The mechanism is intended to be used with data
+   security protections provided by application-layer protocol,
+   generally through its use of Transport Layer Security ([TLS])
+   services.
+
+   By default, implementations SHOULD advertise and make use of the
+   PLAIN mechanism only when adequate data security services are in
+   place.  Specifications for IETF protocols that indicate that this
+   mechanism is an applicable authentication mechanism MUST mandate that
+   implementations support an strong data security service, such as TLS.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [Keywords].
+
+2.  PLAIN SASL Mechanism
+
+   The mechanism consists of a single message, a string of [UTF-8]
+   encoded [Unicode] characters, from the client to the server.  The
+   client presents the authorization identity (identity to act as),
+   followed by a NUL (U+0000) character, followed by the authentication
+   identity (identity whose password will be used), followed by a NUL
+   (U+0000) character, followed by the clear-text password.  As with
+   other SASL mechanisms, the client does not provide an authorization
+   identity when it wishes the server to derive an identity from the
+   credentials and use that as the authorization identity.
+
+
+
+
+Zeilenga                    Standards Track                     [Page 2]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+   The formal grammar for the client message using Augmented BNF [ABNF]
+   follows.
+
+   message   = [authzid] UTF8NUL authcid UTF8NUL passwd
+   authcid   = 1*SAFE ; MUST accept up to 255 octets
+   authzid   = 1*SAFE ; MUST accept up to 255 octets
+   passwd    = 1*SAFE ; MUST accept up to 255 octets
+   UTF8NUL   = %x00 ; UTF-8 encoded NUL character
+
+   SAFE      = UTF1 / UTF2 / UTF3 / UTF4
+               ;; any UTF-8 encoded Unicode character except NUL
+
+   UTF1      = %x01-7F ;; except NUL
+   UTF2      = %xC2-DF UTF0
+   UTF3      = %xE0 %xA0-BF UTF0 / %xE1-EC 2(UTF0) /
+               %xED %x80-9F UTF0 / %xEE-EF 2(UTF0)
+   UTF4      = %xF0 %x90-BF 2(UTF0) / %xF1-F3 3(UTF0) /
+               %xF4 %x80-8F 2(UTF0)
+   UTF0      = %x80-BF
+
+   The authorization identity (authzid), authentication identity
+   (authcid), password (passwd), and NUL character deliminators SHALL be
+   transferred as [UTF-8] encoded strings of [Unicode] characters.  As
+   the NUL (U+0000) character is used as a deliminator, the NUL (U+0000)
+   character MUST NOT appear in authzid, authcid, or passwd productions.
+
+   The form of the authzid production is specific to the application-
+   level protocol's SASL profile [SASL].  The authcid and passwd
+   productions are form-free.  Use of non-visible characters or
+   characters that a user may be unable to enter on some keyboards is
+   discouraged.
+
+   Servers MUST be capable of accepting authzid, authcid, and passwd
+   productions up to and including 255 octets.  It is noted that the
+   UTF-8 encoding of a Unicode character may be as long as 4 octets.
+
+   Upon receipt of the message, the server will verify the presented (in
+   the message) authentication identity (authcid) and password (passwd)
+   with the system authentication database, and it will verify that the
+   authentication credentials permit the client to act as the (presented
+   or derived) authorization identity (authzid).  If both steps succeed,
+   the user is authenticated.
+
+   The presented authentication identity and password strings, as well
+   as the database authentication identity and password strings, are to
+   be prepared before being used in the verification process.  The
+   [SASLPrep] profile of the [StringPrep] algorithm is the RECOMMENDED
+   preparation algorithm.  The SASLprep preparation algorithm is
+
+
+
+Zeilenga                    Standards Track                     [Page 3]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+   recommended to improve the likelihood that comparisons behave in an
+   expected manner.  The SASLprep preparation algorithm is not mandatory
+   so as to allow the server to employ other preparation algorithms
+   (including none) when appropriate.  For instance, use of a different
+   preparation algorithm may be necessary for the server to interoperate
+   with an external system.
+
+   When preparing the presented strings using [SASLPrep], the presented
+   strings are to be treated as "query" strings (Section 7 of
+   [StringPrep]) and hence unassigned code points are allowed to appear
+   in their prepared output.  When preparing the database strings using
+   [SASLPrep], the database strings are to be treated as "stored"
+   strings (Section 7 of [StringPrep]) and hence unassigned code points
+   are prohibited from appearing in their prepared output.
+
+   Regardless of the preparation algorithm used, if the output of a
+   non-invertible function (e.g., hash) of the expected string is
+   stored, the string MUST be prepared before input to that function.
+
+   Regardless of the preparation algorithm used, if preparation fails or
+   results in an empty string, verification SHALL fail.
+
+   When no authorization identity is provided, the server derives an
+   authorization identity from the prepared representation of the
+   provided authentication identity string.  This ensures that the
+   derivation of different representations of the authentication
+   identity produces the same authorization identity.
+
+   The server MAY use the credentials to initialize any new
+   authentication database, such as one suitable for [CRAM-MD5] or
+   [DIGEST-MD5].
+
+3.  Pseudo-Code
+
+   This section provides pseudo-code illustrating the verification
+   process (using hashed passwords and the SASLprep preparation
+   function) discussed above.  This section is not definitive.
+
+   boolean Verify(string authzid, string authcid, string passwd) {
+     string pAuthcid = SASLprep(authcid, true); # prepare authcid
+     string pPasswd = SASLprep(passwd, true);   # prepare passwd
+     if (pAuthcid == NULL || pPasswd == NULL) {
+       return false;     # preparation failed
+     }
+     if (pAuthcid == "" || pPasswd == "") {
+       return false;     # empty prepared string
+     }
+
+
+
+
+Zeilenga                    Standards Track                     [Page 4]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+     storedHash = FetchPasswordHash(pAuthcid);
+     if (storedHash == NULL || storedHash == "") {
+       return false;     # error or unknown authcid
+     }
+
+     if (!Compare(storedHash, Hash(pPasswd))) {
+       return false;     # incorrect password
+     }
+
+     if (authzid == NULL ) {
+       authzid = DeriveAuthzid(pAuthcid);
+       if (authzid == NULL || authzid == "") {
+           return false; # could not derive authzid
+       }
+     }
+
+     if (!Authorize(pAuthcid, authzid)) {
+       return false;     # not authorized
+     }
+
+     return true;
+   }
+
+   The second parameter of the SASLprep function, when true, indicates
+   that unassigned code points are allowed in the input.  When the
+   SASLprep function is called to prepare the password prior to
+   computing the stored hash, the second parameter would be false.
+
+   The second parameter provided to the Authorize function is not
+   prepared by this code.  The application-level SASL profile should be
+   consulted to determine what, if any, preparation is necessary.
+
+   Note that the DeriveAuthzid and Authorize functions (whether
+   implemented as one function or two, whether designed in a manner in
+   which these functions or whether the mechanism implementation can be
+   reused elsewhere) require knowledge and understanding of mechanism
+   and the application-level protocol specification and/or
+   implementation details to implement.
+
+   Note that the Authorize function outcome is clearly dependent on
+   details of the local authorization model and policy.  Both functions
+   may be dependent on other factors as well.
+
+
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 5]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+4.  Examples
+
+   This section provides examples of PLAIN authentication exchanges.
+   The examples are intended to help the readers understand the above
+   text.  The examples are not definitive.
+
+   "C:" and "S:" indicate lines sent by the client and server,
+   respectively.  "<NUL>" represents a single NUL (U+0000) character.
+   The Application Configuration Access Protocol ([ACAP]) is used in the
+   examples.
+
+   The first example shows how the PLAIN mechanism might be used for
+   user authentication.
+
+   S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
+   C: a001 STARTTLS
+   S: a001 OK "Begin TLS negotiation now"
+   <TLS negotiation, further commands are under TLS layer>
+   S: * ACAP (SASL "CRAM-MD5" "PLAIN")
+   C: a002 AUTHENTICATE "PLAIN"
+   S: + ""
+   C: {21}
+   C: <NUL>tim<NUL>tanstaaftanstaaf
+   S: a002 OK "Authenticated"
+
+   The second example shows how the PLAIN mechanism might be used to
+   attempt to assume the identity of another user.  In this example, the
+   server rejects the request.  Also, this example makes use of the
+   protocol optional initial response capability to eliminate a round-
+   trip.
+
+   S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
+   C: a001 STARTTLS
+   S: a001 OK "Begin TLS negotiation now"
+   <TLS negotiation, further commands are under TLS layer>
+   S: * ACAP (SASL "CRAM-MD5" "PLAIN")
+   C: a002 AUTHENTICATE "PLAIN" {20+}
+   C: Ursel<NUL>Kurt<NUL>xipj3plmq
+   S: a002 NO "Not authorized to requested authorization identity"
+
+5.  Security Considerations
+
+   As the PLAIN mechanism itself provided no integrity or
+   confidentiality protections, it should not be used without adequate
+   external data security protection, such as TLS services provided by
+   many application-layer protocols.  By default, implementations SHOULD
+   NOT advertise and SHOULD NOT make use of the PLAIN mechanism unless
+   adequate data security services are in place.
+
+
+
+Zeilenga                    Standards Track                     [Page 6]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+   When the PLAIN mechanism is used, the server gains the ability to
+   impersonate the user to all services with the same password
+   regardless of any encryption provided by TLS or other confidentiality
+   protection mechanisms.  Whereas many other authentication mechanisms
+   have similar weaknesses, stronger SASL mechanisms address this issue.
+   Clients are encouraged to have an operational mode where all
+   mechanisms that are likely to reveal the user's password to the
+   server are disabled.
+
+   General [SASL] security considerations apply to this mechanism.
+
+   Unicode, [UTF-8], and [StringPrep] security considerations also
+   apply.
+
+6.  IANA Considerations
+
+   The SASL Mechanism registry [IANA-SASL] entry for the PLAIN mechanism
+   has been updated by the IANA to reflect that this document now
+   provides its technical specification.
+
+   To: iana@iana.org
+   Subject: Updated Registration of SASL mechanism PLAIN
+
+   SASL mechanism name: PLAIN
+   Security considerations: See RFC 4616.
+   Published specification (optional, recommended): RFC 4616
+   Person & email address to contact for further information:
+        Kurt Zeilenga <kurt@openldap.org>
+        IETF SASL WG <ietf-sasl@imc.org>
+   Intended usage: COMMON
+   Author/Change controller: IESG <iesg@ietf.org>
+   Note: Updates existing entry for PLAIN
+
+7.  Acknowledgements
+
+   This document is a revision of RFC 2595 by Chris Newman.  Portions of
+   the grammar defined in Section 2 were borrowed from [UTF-8] by
+   Francois Yergeau.
+
+   This document is a product of the IETF Simple Authentication and
+   Security Layer (SASL) Working Group.
+
+
+
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 7]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+8.  Normative References
+
+   [ABNF]        Crocker, D., Ed. and P. Overell, "Augmented BNF for
+                 Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+   [Keywords]    Bradner, S., "Key words for use in RFCs to Indicate
+                 Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [SASL]        Melnikov, A., Ed., and K. Zeilenga, Ed., "Simple
+                 Authentication and Security Layer (SASL)", RFC 4422,
+                 June 2006.
+
+   [SASLPrep]    Zeilenga, K., "SASLprep: Stringprep Profile for User
+                 Names and Passwords", RFC 4013, February 2005.
+
+   [StringPrep]  Hoffman, P. and M. Blanchet, "Preparation of
+                 Internationalized Strings ("stringprep")", RFC 3454,
+                 December 2002.
+
+   [Unicode]     The Unicode Consortium, "The Unicode Standard, Version
+                 3.2.0" is defined by "The Unicode Standard, Version
+                 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
+                 61633-5), as amended by the "Unicode Standard Annex
+                 #27: Unicode 3.1"
+                 (http://www.unicode.org/reports/tr27/) and by the
+                 "Unicode Standard Annex #28: Unicode 3.2"
+                 (http://www.unicode.org/reports/tr28/).
+
+   [UTF-8]       Yergeau, F., "UTF-8, a transformation format of ISO
+                 10646", STD 63, RFC 3629, November 2003.
+
+   [TLS]         Dierks, T. and E. Rescorla, "The Transport Layer
+                 Security (TLS) Protocol Version 1.1", RFC 4346, April
+                 2006.
+
+9.  Informative References
+
+   [ACAP]        Newman, C. and J. Myers, "ACAP -- Application
+                 Configuration Access Protocol", RFC 2244, November
+                 1997.
+
+   [CRAM-MD5]    Nerenberg, L., Ed., "The CRAM-MD5 SASL Mechanism", Work
+                 in Progress, June 2006.
+
+   [DIGEST-MD5]  Melnikov, A., Ed., "Using Digest Authentication as a
+                 SASL Mechanism", Work in Progress, June 2006.
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 8]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+   [IANA-SASL]   IANA, "SIMPLE AUTHENTICATION AND SECURITY LAYER (SASL)
+                 MECHANISMS",
+                 <http://www.iana.org/assignments/sasl-mechanisms>.
+
+   [SMTP-AUTH]   Myers, J., "SMTP Service Extension for Authentication",
+                 RFC 2554, March 1999.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 9]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+Appendix A.  Changes since RFC 2595
+
+   This appendix is non-normative.
+
+   This document replaces Section 6 of RFC 2595.
+
+   The specification details how the server is to compare client-
+   provided character strings with stored character strings.
+
+   The ABNF grammar was updated.  In particular, the grammar now allows
+   LINE FEED (U+000A) and CARRIAGE RETURN (U+000D) characters in the
+   authzid, authcid, passwd productions.  However, whether these control
+   characters may be used depends on the string preparation rules
+   applicable to the production.  For passwd and authcid productions,
+   control characters are prohibited.  For authzid, one must consult the
+   application-level SASL profile.  This change allows PLAIN to carry
+   all possible authorization identity strings allowed in SASL.
+
+   Pseudo-code was added.
+
+   The example section was expanded to illustrate more features of the
+   PLAIN mechanism.
+
+Editor's Address
+
+   Kurt D. Zeilenga
+   OpenLDAP Foundation
+
+   EMail: Kurt@OpenLDAP.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                    [Page 10]
+
+RFC 4616                The PLAIN SASL Mechanism             August 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is provided by the IETF
+   Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Zeilenga                    Standards Track                    [Page 11]
+
diff --git a/imap/docs/rfc/rfc4731.txt b/imap/docs/rfc/rfc4731.txt
new file mode 100644
index 00000000..8c4869aa
--- /dev/null
+++ b/imap/docs/rfc/rfc4731.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group                                        A. Melnikov
+Request for Comments: 4731                                     Isode Ltd
+Category: Standards Track                                    D. Cridland
+                                                   Inventure Systems Ltd
+                                                           November 2006
+
+
+           IMAP4 Extension to SEARCH Command for Controlling
+                  What Kind of Information Is Returned
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The IETF Trust (2006).
+
+Abstract
+
+   This document extends IMAP (RFC 3501) SEARCH and UID SEARCH commands
+   with several result options, which can control what kind of
+   information is returned. The following result options are defined:
+   minimal value, maximal value, all found messages, and number of found
+   messages.
+
+Table of Contents
+
+   1. Introduction ....................................................2
+   2. Conventions Used in This Document ...............................2
+   3. IMAP Protocol Changes ...........................................2
+      3.1. New SEARCH/UID SEARCH Result Options .......................2
+      3.2. Interaction with CONDSTORE extension .......................4
+   4. Formal Syntax ...................................................5
+   5. Security Considerations .........................................6
+   6. IANA Considerations .............................................6
+   7. Normative References ............................................6
+   8. Acknowledgments .................................................6
+
+
+
+
+
+
+
+
+
+Melnikov & Cridland         Standards Track                     [Page 1]
+
+RFC 4731               IMAP4 Extension to SEARCH           November 2006
+
+
+1.  Introduction
+
+   [IMAPABNF] extended SEARCH and UID SEARCH commands with result
+   specifiers (also known as result options), which can control what
+   kind of information is returned.
+
+   A server advertising the ESEARCH capability supports the following
+   result options:  minimal value, maximal value, all found messages,
+   and number of found messages.  These result options allow clients to
+   get SEARCH results in more convenient forms, while also saving
+   bandwidth required to transport the results, for example, by finding
+   the first unseen message or returning the number of unseen or deleted
+   messages.  Also, when a single MIN or a single MAX result option is
+   specified, servers can optimize execution of SEARCHes.
+
+2.  Conventions Used in This Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+3.   IMAP Protocol Changes
+
+3.1.  New SEARCH/UID SEARCH Result Options
+
+   The SEARCH/UID SEARCH commands are extended to allow for the
+   following result options:
+
+      MIN
+         Return the lowest message number/UID that satisfies the SEARCH
+         criteria.
+
+         If the SEARCH results in no matches, the server MUST NOT
+         include the MIN result option in the ESEARCH response; however,
+         it still MUST send the ESEARCH response.
+
+      MAX
+         Return the highest message number/UID that satisfies the SEARCH
+         criteria.
+
+         If the SEARCH results in no matches, the server MUST NOT
+         include the MAX result option in the ESEARCH response; however,
+         it still MUST send the ESEARCH response.
+
+
+
+
+
+Melnikov & Cridland         Standards Track                     [Page 2]
+
+RFC 4731               IMAP4 Extension to SEARCH           November 2006
+
+
+      ALL
+         Return all message numbers/UIDs that satisfy the SEARCH
+         criteria.  Unlike regular (unextended) SEARCH, the messages are
+         always returned using the sequence-set syntax.  A sequence-set
+         representation may be more compact and can be used as is in a
+         subsequent command that accepts sequence-set.  Note, the client
+         MUST NOT assume that messages/UIDs will be listed in any
+         particular order.
+
+         If the SEARCH results in no matches, the server MUST NOT
+         include the ALL result option in the ESEARCH response; however,
+         it still MUST send the ESEARCH response.
+
+      COUNT
+         Return number of the messages that satisfy the SEARCH criteria.
+         This result option MUST always be included in the ESEARCH
+         response.
+
+   If one or more result options described above are specified, the
+   extended SEARCH command MUST return a single ESEARCH response
+   [IMAPABNF], instead of the SEARCH response.
+
+   An extended UID SEARCH command MUST cause an ESEARCH response with
+   the UID indicator present.
+
+   Note that future extensions to this document can allow servers to
+   return multiple ESEARCH responses for a single extended SEARCH
+   command.  These extensions will have to describe how results from
+   multiple ESEARCH responses are to be amalgamated.
+
+   If the list of result options is empty, that requests the server to
+   return an ESEARCH response instead of the SEARCH response.  This is
+   equivalent to "(ALL)".
+
+      Example:    C: A282 SEARCH RETURN (MIN COUNT) FLAGGED
+                     SINCE 1-Feb-1994 NOT FROM "Smith"
+                  S: * ESEARCH (TAG "A282") MIN 2 COUNT 3
+                  S: A282 OK SEARCH completed
+
+      Example:    C: A283 SEARCH RETURN () FLAGGED
+                     SINCE 1-Feb-1994 NOT FROM "Smith"
+                  S: * ESEARCH (TAG "A283") ALL 2,10:11
+                  S: A283 OK SEARCH completed
+
+   The following example demonstrates finding the first unseen message
+   as returned in the UNSEEN response code on a successful SELECT
+   command:
+
+
+
+
+Melnikov & Cridland         Standards Track                     [Page 3]
+
+RFC 4731               IMAP4 Extension to SEARCH           November 2006
+
+
+      Example:    C: A284 SEARCH RETURN (MIN) UNSEEN
+                  S: * ESEARCH (TAG "A284") MIN 4
+                  S: A284 OK SEARCH completed
+
+   The following example demonstrates that if the ESEARCH UID indicator
+   is present, all data in the ESEARCH response is referring to UIDs;
+   for example, the MIN result specifier will be followed by a UID.
+
+      Example:    C: A285 UID SEARCH RETURN (MIN MAX) 1:5000
+                  S: * ESEARCH (TAG "A285") UID MIN 7 MAX 3800
+                  S: A285 OK SEARCH completed
+
+   The following example demonstrates returning the number of deleted
+   messages:
+
+      Example:    C: A286 SEARCH RETURN (COUNT) DELETED
+                  S: * ESEARCH (TAG "A286") COUNT 15
+                  S: A286 OK SEARCH completed
+
+3.2.  Interaction with CONDSTORE extension
+
+   When the server supports both the ESEARCH and the CONDSTORE
+   [CONDSTORE] extension, and the client requests one or more result
+   option described in section 3.1 together with the MODSEQ search
+   criterion in the same SEARCH/UID SEARCH command, then the server MUST
+   return the ESEARCH response containing the MODSEQ result option
+   (described in the following paragraph) instead of the extended SEARCH
+   response described in section 3.5 of [CONDSTORE].
+
+   If the SEARCH/UID SEARCH command contained a single MIN or MAX result
+   option, the MODSEQ result option contains the mod-sequence for the
+   found message.  If the SEARCH/UID SEARCH command contained both MIN
+   and MAX result options and no ALL/COUNT option, the MODSEQ result
+   option contains the highest mod-sequence for the two returned
+   messages.  Otherwise the MODSEQ result option contains the highest
+   mod-sequence for all messages being returned.
+
+   Example: The following example demonstrates how Example 15 from
+   [CONDSTORE] would look in the presence of one or more result option:
+
+         C: a1 SEARCH RETURN (MIN) MODSEQ "/flags/\\draft"
+             all 620162338
+         S: * ESEARCH (TAG "a1") MIN 2 MODSEQ 917162488
+         S: a1 OK Search complete
+
+         C: a2 SEARCH RETURN (MAX) MODSEQ "/flags/\\draft"
+             all 620162338
+         S: * ESEARCH (TAG "a2") MAX 23 MODSEQ 907162321
+
+
+
+Melnikov & Cridland         Standards Track                     [Page 4]
+
+RFC 4731               IMAP4 Extension to SEARCH           November 2006
+
+
+         S: a2 OK Search complete
+
+         C: a3 SEARCH RETURN (MIN MAX) MODSEQ "/flags/\\draft"
+             all 620162338
+         S: * ESEARCH (TAG "a3") MIN 2 MAX 23 MODSEQ 917162488
+         S: a3 OK Search complete
+
+         C: a4 SEARCH RETURN (MIN COUNT) MODSEQ "/flags/\\draft"
+             all 620162338
+         S: * ESEARCH (TAG "a4") MIN 2 COUNT 10 MODSEQ 917162500
+         S: a4 OK Search complete
+
+4.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].
+
+   Non-terminals referenced but not defined below are as defined by
+   [IMAP4], [CONDSTORE], or [IMAPABNF].
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper or lowercase characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+     capability         =/ "ESEARCH"
+
+     search-return-data = "MIN" SP nz-number /
+                          "MAX" SP nz-number /
+                          "ALL" SP sequence-set /
+                          "COUNT" SP number
+                          ;; conforms to the generic
+                          ;; search-return-data syntax defined
+                          ;; in [IMAPABNF]
+
+     search-return-opt  = "MIN" / "MAX" / "ALL" / "COUNT"
+                          ;; conforms to generic search-return-opt
+                          ;; syntax defined in [IMAPABNF]
+
+     When the CONDSTORE [CONDSTORE] IMAP extension is also supported,
+     the ABNF is updated as follows:
+
+     search-return-data =/ "MODSEQ" SP mod-sequence-value
+                          ;; mod-sequence-value is defined
+                          ;; in [CONDSTORE]
+
+
+
+
+
+
+Melnikov & Cridland         Standards Track                     [Page 5]
+
+RFC 4731               IMAP4 Extension to SEARCH           November 2006
+
+
+5.  Security Considerations
+
+   In the general case, the IMAP SEARCH/UID SEARCH commands can be CPU
+   and/or IO intensive, and are seen by some as a potential attack point
+   for denial of service attacks, so some sites/implementations even
+   disable them entirely.  This is quite unfortunate, as SEARCH command
+   is one of the best examples demonstrating IMAP advantage over POP3.
+
+   The ALL and COUNT return options don't change how SEARCH is working
+   internally; they only change how information about found messages is
+   returned.  MIN and MAX SEARCH result options described in this
+   document can lighten the load on IMAP servers that choose to optimize
+   SEARCHes containing only one or both of them.
+
+   It is believed that this extension doesn't raise any additional
+   security concerns not already discussed in [IMAP4].
+
+6.  IANA Considerations
+
+   IMAP4 capabilities are registered by publishing a standards track RFC
+   or an IESG-approved experimental RFC.  The registry is currently
+   located at <http://www.iana.org/assignments/imap4-capabilities>.
+
+   This document defines the ESEARCH IMAP capability, which IANA added
+   to the registry.
+
+7.  Normative References
+
+   [KEYWORDS]  Bradner, S., "Key words for use in RFCs to Indicate
+               Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [IMAP4]     Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+               4rev1", RFC 3501, March 2003.
+
+   [ABNF]      Crocker, D. (Ed.) and P. Overell , "Augmented BNF for
+               Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+   [IMAPABNF]  Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
+               ABNF", RFC 4466, April 2006..
+
+   [CONDSTORE] Melnikov, A. and S. Hole, "IMAP Extension for Conditional
+               STORE", RFC 4551, June 2006.
+
+8.  Acknowledgments
+
+   Thanks to Michael Wener, Arnt Gulbrandsen, Cyrus Daboo, Mark Crispin,
+   and Pete Maclean for comments and corrections.
+
+
+
+
+Melnikov & Cridland         Standards Track                     [Page 6]
+
+RFC 4731               IMAP4 Extension to SEARCH           November 2006
+
+
+Authors' Addresses
+
+   Alexey Melnikov
+   Isode Limited
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex, TW12 2BX
+   UK
+
+   EMail: Alexey.Melnikov@isode.com
+
+
+   Dave A. Cridland
+   Inventure Systems Limited
+
+   EMail: dave.cridland@inventuresystems.co.uk
+   URL: http://invsys.co.uk/dave/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Cridland         Standards Track                     [Page 7]
+
+RFC 4731               IMAP4 Extension to SEARCH           November 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST,
+   AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
+   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
+   THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
+   IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
+   PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+Melnikov & Cridland         Standards Track                     [Page 8]
+
diff --git a/imap/docs/rfc/rfc4752.txt b/imap/docs/rfc/rfc4752.txt
new file mode 100644
index 00000000..bfd8e30b
--- /dev/null
+++ b/imap/docs/rfc/rfc4752.txt
@@ -0,0 +1,563 @@
+
+
+
+
+
+
+Network Working Group                                   A. Melnikov, Ed.
+Request for Comments: 4752                                         Isode
+Obsoletes: 2222                                            November 2006
+Category: Standards Track
+
+
+                       The Kerberos V5 ("GSSAPI")
+       Simple Authentication and Security Layer (SASL) Mechanism
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The IETF Trust (2006).
+
+Abstract
+
+   The Simple Authentication and Security Layer (SASL) is a framework
+   for adding authentication support to connection-based protocols.
+   This document describes the method for using the Generic Security
+   Service Application Program Interface (GSS-API) Kerberos V5 in the
+   SASL.
+
+   This document replaces Section 7.2 of RFC 2222, the definition of the
+   "GSSAPI" SASL mechanism.  This document, together with RFC 4422,
+   obsoletes RFC 2222.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 1]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+Table of Contents
+
+   1. Introduction ....................................................2
+      1.1. Relationship to Other Documents ............................2
+   2. Conventions Used in This Document ...............................2
+   3. Kerberos V5 GSS-API Mechanism ...................................2
+      3.1. Client Side of Authentication Protocol Exchange ............3
+      3.2. Server Side of Authentication Protocol Exchange ............4
+      3.3. Security Layer .............................................6
+   4. IANA Considerations .............................................7
+   5. Security Considerations .........................................7
+   6. Acknowledgements ................................................8
+   7. Changes since RFC 2222 ..........................................8
+   8. References ......................................................8
+      8.1. Normative References .......................................8
+      8.2. Informative References .....................................9
+
+1.  Introduction
+
+   This specification documents currently deployed Simple Authentication
+   and Security Layer (SASL [SASL]) mechanism supporting the Kerberos V5
+   [KERBEROS] Generic Security Service Application Program Interface
+   ([GSS-API]) mechanism [RFC4121].  The authentication sequence is
+   described in Section 3.  Note that the described authentication
+   sequence has known limitations, in particular, it lacks channel
+   bindings and the number of round-trips required to complete
+   authentication exchange is not minimal.  SASL WG is working on a
+   separate document that should address these limitations.
+
+1.1.  Relationship to Other Documents
+
+   This document, together with RFC 4422, obsoletes RFC 2222 in its
+   entirety.  This document replaces Section 7.2 of RFC 2222.  The
+   remainder is obsoleted as detailed in Section 1.2 of RFC 4422.
+
+2.  Conventions Used in This Document
+
+   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+   in this document are to be interpreted as defined in "Key words for
+   use in RFCs to Indicate Requirement Levels" [KEYWORDS].
+
+3.  Kerberos V5 GSS-API Mechanism
+
+   The SASL mechanism name for the Kerberos V5 GSS-API mechanism
+   [RFC4121] is "GSSAPI".  Though known as the SASL GSSAPI mechanism,
+   the mechanism is specifically tied to Kerberos V5 and GSS-API's
+   Kerberos V5 mechanism.
+
+
+
+
+Melnikov                    Standards Track                     [Page 2]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+   The GSSAPI SASL mechanism is a "client goes first" SASL mechanism;
+   i.e., it starts with the client sending a "response" created as
+   described in the following section.
+
+   The implementation MAY set any GSS-API flags or arguments not
+   mentioned in this specification as is necessary for the
+   implementation to enforce its security policy.
+
+   Note that major status codes returned by GSS_Init_sec_context() or
+   GSS_Accept_sec_context() other than GSS_S_COMPLETE or
+   GSS_S_CONTINUE_NEEDED cause authentication failure.  Major status
+   codes returned by GSS_Unwrap() other than GSS_S_COMPLETE (without any
+   additional supplementary status codes) cause authentication and/or
+   security layer failure.
+
+3.1.  Client Side of Authentication Protocol Exchange
+
+   The client calls GSS_Init_sec_context, passing in
+   input_context_handle of 0 (initially), mech_type of the Kerberos V5
+   GSS-API mechanism [KRB5GSS], chan_binding of NULL, and targ_name
+   equal to output_name from GSS_Import_Name called with input_name_type
+   of GSS_C_NT_HOSTBASED_SERVICE (*) and input_name_string of
+   "service@hostname" where "service" is the service name specified in
+   the protocol's profile, and "hostname" is the fully qualified host
+   name of the server.  When calling the GSS_Init_sec_context, the
+   client MUST pass the integ_req_flag of TRUE (**).  If the client will
+   be requesting a security layer, it MUST also supply to the
+   GSS_Init_sec_context a mutual_req_flag of TRUE, and a
+   sequence_req_flag of TRUE.  If the client will be requesting a
+   security layer providing confidentiality protection, it MUST also
+   supply to the GSS_Init_sec_context a conf_req_flag of TRUE.  The
+   client then responds with the resulting output_token.  If
+   GSS_Init_sec_context returns GSS_S_CONTINUE_NEEDED, then the client
+   should expect the server to issue a token in a subsequent challenge.
+   The client must pass the token to another call to
+   GSS_Init_sec_context, repeating the actions in this paragraph.
+
+   (*) Clients MAY use name types other than GSS_C_NT_HOSTBASED_SERVICE
+   to import servers' acceptor names, but only when they have a priori
+   knowledge that the servers support alternate name types.  Otherwise
+   clients MUST use GSS_C_NT_HOSTBASED_SERVICE for importing acceptor
+   names.
+
+   (**) Note that RFC 2222 [RFC2222] implementations will not work with
+   GSS-API implementations that require integ_req_flag to be true.  No
+   implementations of RFC 1964 [KRB5GSS] or RFC 4121 [RFC4121] that
+   require integ_req_flag to be true are believed to exist and it is
+   expected that any future update to [RFC4121] will require that
+
+
+
+Melnikov                    Standards Track                     [Page 3]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+   integrity be available even in not explicitly requested by the
+   application.
+
+   When GSS_Init_sec_context returns GSS_S_COMPLETE, the client examines
+   the context to ensure that it provides a level of protection
+   permitted by the client's security policy.  In particular, if the
+   integ_avail flag is not set in the context, then no security layer
+   can be offered or accepted.
+
+   If the conf_avail flag is not set in the context, then no security
+   layer with confidentiality can be offered or accepted.  If the
+   context is acceptable, the client takes the following actions: If the
+   last call to GSS_Init_sec_context returned an output_token, then the
+   client responds with the output_token, otherwise the client responds
+   with no data.  The client should then expect the server to issue a
+   token in a subsequent challenge.  The client passes this token to
+   GSS_Unwrap and interprets the first octet of resulting cleartext as a
+   bit-mask specifying the security layers supported by the server and
+   the second through fourth octets as the maximum size output_message
+   the server is able to receive (in network byte order).  If the
+   resulting cleartext is not 4 octets long, the client fails the
+   negotiation.  The client verifies that the server maximum buffer is 0
+   if the server does not advertise support for any security layer.
+
+   The client then constructs data, with the first octet containing the
+   bit-mask specifying the selected security layer, the second through
+   fourth octets containing in network byte order the maximum size
+   output_message the client is able to receive (which MUST be 0 if the
+   client does not support any security layer), and the remaining octets
+   containing the UTF-8 [UTF8] encoded authorization identity.
+   (Implementation note: The authorization identity is not terminated
+   with the zero-valued (%x00) octet (e.g., the UTF-8 encoding of the
+   NUL (U+0000) character)).  The client passes the data to GSS_Wrap
+   with conf_flag set to FALSE and responds with the generated
+   output_message.  The client can then consider the server
+   authenticated.
+
+3.2.  Server Side of Authentication Protocol Exchange
+
+   A server MUST NOT advertise support for the "GSSAPI" SASL mechanism
+   described in this document unless it has acceptor credential for the
+   Kerberos V GSS-API mechanism [KRB5GSS].
+
+   The server passes the initial client response to
+   GSS_Accept_sec_context as input_token, setting input_context_handle
+   to 0 (initially), chan_binding of NULL, and a suitable
+   acceptor_cred_handle (see below).  If GSS_Accept_sec_context returns
+   GSS_S_CONTINUE_NEEDED, the server returns the generated output_token
+
+
+
+Melnikov                    Standards Track                     [Page 4]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+   to the client in challenge and passes the resulting response to
+   another call to GSS_Accept_sec_context, repeating the actions in this
+   paragraph.
+
+   Servers SHOULD use a credential obtained by calling GSS_Acquire_cred
+   or GSS_Add_cred for the GSS_C_NO_NAME desired_name and the Object
+   Identifier (OID) of the Kerberos V5 GSS-API mechanism [KRB5GSS](*).
+   Servers MAY use GSS_C_NO_CREDENTIAL as an acceptor credential handle.
+   Servers MAY use a credential obtained by calling GSS_Acquire_cred or
+   GSS_Add_cred for the server's principal name(s) (**) and the Kerberos
+   V5 GSS-API mechanism [KRB5GSS].
+
+   (*) Unlike GSS_Add_cred the GSS_Acquire_cred uses an OID set of GSS-
+   API mechanism as an input parameter.  The OID set can be created by
+   using GSS_Create_empty_OID_set and GSS_Add_OID_set_member.  It can be
+   freed by calling the GSS_Release_oid_set.
+
+
+   (**) Use of server's principal names having
+   GSS_C_NT_HOSTBASED_SERVICE name type and "service@hostname" format,
+   where "service" is the service name specified in the protocol's
+   profile, and "hostname" is the fully qualified host name of the
+   server, is RECOMMENDED.  The server name is generated by calling
+   GSS_Import_name with input_name_type of GSS_C_NT_HOSTBASED_SERVICE
+   and input_name_string of "service@hostname".
+
+   Upon successful establishment of the security context (i.e.,
+   GSS_Accept_sec_context returns GSS_S_COMPLETE), the server SHOULD
+   verify that the negotiated GSS-API mechanism is indeed Kerberos V5
+   [KRB5GSS].  This is done by examining the value of the mech_type
+   parameter returned from the GSS_Accept_sec_context call.  If the
+   value differs, SASL authentication MUST be aborted.
+
+   Upon successful establishment of the security context and if the
+   server used GSS_C_NO_NAME/GSS_C_NO_CREDENTIAL to create acceptor
+   credential handle, the server SHOULD also check using the
+   GSS_Inquire_context that the target_name used by the client matches
+   either
+
+   -  the GSS_C_NT_HOSTBASED_SERVICE "service@hostname" name syntax,
+      where "service" is the service name specified in the application
+      protocol's profile,
+
+      or
+
+   -  the GSS_KRB5_NT_PRINCIPAL_NAME [KRB5GSS] name syntax for a two-
+      component principal where the first component matches the service
+      name specified in the application protocol's profile.
+
+
+
+Melnikov                    Standards Track                     [Page 5]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+   When GSS_Accept_sec_context returns GSS_S_COMPLETE, the server
+   examines the context to ensure that it provides a level of protection
+   permitted by the server's security policy.  In particular, if the
+   integ_avail flag is not set in the context, then no security layer
+   can be offered or accepted.  If the conf_avail flag is not set in the
+   context, then no security layer with confidentiality can be offered
+   or accepted.
+
+   If the context is acceptable, the server takes the following actions:
+   If the last call to GSS_Accept_sec_context returned an output_token,
+   the server returns it to the client in a challenge and expects a
+   reply from the client with no data.  Whether or not an output_token
+   was returned (and after receipt of any response from the client to
+   such an output_token), the server then constructs 4 octets of data,
+   with the first octet containing a bit-mask specifying the security
+   layers supported by the server and the second through fourth octets
+   containing in network byte order the maximum size output_token the
+   server is able to receive (which MUST be 0 if the server does not
+   support any security layer).  The server must then pass the plaintext
+   to GSS_Wrap with conf_flag set to FALSE and issue the generated
+   output_message to the client in a challenge.
+
+   The server must then pass the resulting response to GSS_Unwrap and
+   interpret the first octet of resulting cleartext as the bit-mask for
+   the selected security layer, the second through fourth octets as the
+   maximum size output_message the client is able to receive (in network
+   byte order), and the remaining octets as the authorization identity.
+   The server verifies that the client has selected a security layer
+   that was offered and that the client maximum buffer is 0 if no
+   security layer was chosen.  The server must verify that the src_name
+   is authorized to act as the authorization identity.  After these
+   verifications, the authentication process is complete.  The server is
+   not expected to return any additional data with the success
+   indicator.
+
+3.3.  Security Layer
+
+   The security layers and their corresponding bit-masks are as follows:
+
+          1 No security layer
+          2 Integrity protection.
+            Sender calls GSS_Wrap with conf_flag set to FALSE
+          4 Confidentiality protection.
+            Sender calls GSS_Wrap with conf_flag set to TRUE
+
+   Other bit-masks may be defined in the future; bits that are not
+   understood must be negotiated off.
+
+
+
+
+Melnikov                    Standards Track                     [Page 6]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+   When decoding any received data with GSS_Unwrap, the major_status
+   other than the GSS_S_COMPLETE MUST be treated as a fatal error.
+
+   Note that SASL negotiates the maximum size of the output_message to
+   send.  Implementations can use the GSS_Wrap_size_limit call to
+   determine the corresponding maximum size input_message.
+
+4.  IANA Considerations
+
+   IANA modified the existing registration for "GSSAPI" as follows:
+
+   Family of SASL mechanisms:  NO
+
+   SASL mechanism name:  GSSAPI
+
+   Security considerations:  See Section 5 of RFC 4752
+
+   Published specification:  RFC 4752
+
+   Person & email address to contact for further information:
+      Alexey Melnikov <Alexey.Melnikov@isode.com>
+
+   Intended usage:  COMMON
+
+   Owner/Change controller:  iesg@ietf.org
+
+   Additional information:  This mechanism is for the Kerberos V5
+      mechanism of GSS-API.
+
+5.  Security Considerations
+
+   Security issues are discussed throughout this memo.
+
+   When constructing the input_name_string, the client SHOULD NOT
+   canonicalize the server's fully qualified domain name using an
+   insecure or untrusted directory service.
+
+   For compatibility with deployed software, this document requires that
+   the chan_binding (channel bindings) parameter to GSS_Init_sec_context
+   and GSS_Accept_sec_context be NULL, hence disallowing use of GSS-API
+   support for channel bindings.  GSS-API channel bindings in SASL is
+   expected to be supported via a new GSS-API family of SASL mechanisms
+   (to be introduced in a future document).
+
+   Additional security considerations are in the [SASL] and [GSS-API]
+   specifications.  Additional security considerations for the GSS-API
+   mechanism can be found in [KRB5GSS] and [KERBEROS].
+
+
+
+
+Melnikov                    Standards Track                     [Page 7]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+6.  Acknowledgements
+
+   This document replaces Section 7.2 of RFC 2222 [RFC2222] by John G.
+   Myers.  He also contributed significantly to this revision.
+
+   Lawrence Greenfield converted text of this document to the XML
+   format.
+
+   Contributions of many members of the SASL mailing list are gratefully
+   acknowledged, in particular comments from Chris Newman, Nicolas
+   Williams, Jeffrey Hutzelman, Sam Hartman, Mark Crispin, and Martin
+   Rex.
+
+7.  Changes since RFC 2222
+
+   RFC 2078 [RFC2078] specifies the version of GSS-API used by RFC 2222
+   [RFC2222], which provided the original version of this specification.
+   That version of GSS-API did not provide the integ_integ_avail flag as
+   an input to GSS_Init_sec_context.  Instead, integrity was always
+   requested.  RFC 4422 [SASL] requires that when possible, the security
+   layer negotiation be integrity protected.  To meet this requirement
+   and as part of moving from RFC 2078 [RFC2078] to RFC 2743 [GSS-API],
+   this specification requires that clients request integrity from
+   GSS_Init_sec_context so they can use GSS_Wrap to protect the security
+   layer negotiation.  This specification does not require that the
+   mechanism offer the integrity security layer, simply that the
+   security layer negotiation be wrapped.
+
+8.  References
+
+8.1.  Normative References
+
+   [GSS-API]  Linn, J., "Generic Security Service Application Program
+              Interface Version 2, Update 1", RFC 2743, January 2000.
+
+   [KERBEROS] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
+              Kerberos Network Authentication Service (V5)", RFC 4120,
+              July 2005.
+
+   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [KRB5GSS]  Linn, J., "The Kerberos Version 5 GSS-API Mechanism", RFC
+              1964, June 1996.
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 8]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+   [RFC4121]  Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos
+              Version 5 Generic Security Service Application Program
+              Interface (GSS-API) Mechanism: Version 2", RFC 4121, July
+              2005.
+
+   [SASL]     Melnikov, A. and  K. Zeilenga, "Simple Authentication and
+              Security Layer (SASL)", RFC 4422, June 2006.
+
+   [UTF8]     Yergeau, F., "UTF-8, a transformation format of ISO
+              10646", STD 63, RFC 3629, November 2003.
+
+8.2.  Informative References
+
+   [RFC2078]  Linn, J., "Generic Security Service Application Program
+              Interface, Version 2", RFC 2078, January 1997.
+
+   [RFC2222]  Myers, J., "Simple Authentication and Security Layer
+              (SASL)", RFC 2222, October 1997.
+
+Editor's Address
+
+   Alexey Melnikov
+   Isode Limited
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex  TW12 2BX
+   UK
+
+   EMail: Alexey.Melnikov@isode.com
+   URI:   http://www.melnikov.ca/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov                    Standards Track                     [Page 9]
+
+RFC 4752                 SASL GSSAPI Mechanism             November 2006
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2006).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST,
+   AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
+   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
+   THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
+   IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
+   PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
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+
+Melnikov                    Standards Track                    [Page 10]
+
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+
+Network Working Group                                          C. Newman
+Request for Comments: 4790                              Sun Microsystems
+Category: Standards Track                                      M. Duerst
+                                                Aoyama Gakuin University
+                                                          A. Gulbrandsen
+                                                                    Oryx
+                                                              March 2007
+
+
+            Internet Application Protocol Collation Registry
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The IETF Trust (2007).
+
+Abstract
+
+   Many Internet application protocols include string-based lookup,
+   searching, or sorting operations.  However, the problem space for
+   searching and sorting international strings is large, not fully
+   explored, and is outside the area of expertise for the Internet
+   Engineering Task Force (IETF).  Rather than attempt to solve such a
+   large problem, this specification creates an abstraction framework so
+   that application protocols can precisely identify a comparison
+   function, and the repertoire of comparison functions can be extended
+   in the future.
+
+
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+Newman, et al.              Standards Track                     [Page 1]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+Table of Contents
+
+   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
+     1.1.  Conventions Used in This Document  . . . . . . . . . . . .  4
+   2.  Collation Definition and Purpose . . . . . . . . . . . . . . .  4
+     2.1.  Definition . . . . . . . . . . . . . . . . . . . . . . . .  4
+     2.2.  Purpose  . . . . . . . . . . . . . . . . . . . . . . . . .  4
+     2.3.  Some Other Terms Used in this Document . . . . . . . . . .  5
+     2.4.  Sort Keys  . . . . . . . . . . . . . . . . . . . . . . . .  5
+   3.  Collation Identifier Syntax  . . . . . . . . . . . . . . . . .  6
+     3.1.  Basic Syntax . . . . . . . . . . . . . . . . . . . . . . .  6
+     3.2.  Wildcards  . . . . . . . . . . . . . . . . . . . . . . . .  6
+     3.3.  Ordering Direction . . . . . . . . . . . . . . . . . . . .  7
+     3.4.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
+     3.5.  Naming Guidelines  . . . . . . . . . . . . . . . . . . . .  7
+   4.  Collation Specification Requirements . . . . . . . . . . . . .  8
+     4.1.  Collation/Server Interface . . . . . . . . . . . . . . . .  8
+     4.2.  Operations Supported . . . . . . . . . . . . . . . . . . .  8
+       4.2.1.  Validity . . . . . . . . . . . . . . . . . . . . . . .  9
+       4.2.2.  Equality . . . . . . . . . . . . . . . . . . . . . . .  9
+       4.2.3.  Substring  . . . . . . . . . . . . . . . . . . . . . .  9
+       4.2.4.  Ordering . . . . . . . . . . . . . . . . . . . . . . . 10
+     4.3.  Sort Keys  . . . . . . . . . . . . . . . . . . . . . . . . 10
+     4.4.  Use of Lookup Tables . . . . . . . . . . . . . . . . . . . 11
+   5.  Application Protocol Requirements  . . . . . . . . . . . . . . 11
+     5.1.  Character Encoding . . . . . . . . . . . . . . . . . . . . 11
+     5.2.  Operations . . . . . . . . . . . . . . . . . . . . . . . . 11
+     5.3.  Wildcards  . . . . . . . . . . . . . . . . . . . . . . . . 12
+     5.4.  String Comparison  . . . . . . . . . . . . . . . . . . . . 12
+     5.5.  Disconnected Clients . . . . . . . . . . . . . . . . . . . 12
+     5.6.  Error Codes  . . . . . . . . . . . . . . . . . . . . . . . 13
+     5.7.  Octet Collation  . . . . . . . . . . . . . . . . . . . . . 13
+   6.  Use by Existing Protocols  . . . . . . . . . . . . . . . . . . 13
+   7.  Collation Registration . . . . . . . . . . . . . . . . . . . . 14
+     7.1.  Collation Registration Procedure . . . . . . . . . . . . . 14
+     7.2.  Collation Registration Format  . . . . . . . . . . . . . . 15
+       7.2.1.  Registration Template  . . . . . . . . . . . . . . . . 15
+       7.2.2.  The Collation Element  . . . . . . . . . . . . . . . . 15
+       7.2.3.  The Identifier Element . . . . . . . . . . . . . . . . 16
+       7.2.4.  The Title Element  . . . . . . . . . . . . . . . . . . 16
+       7.2.5.  The Operations Element . . . . . . . . . . . . . . . . 16
+       7.2.6.  The Specification Element  . . . . . . . . . . . . . . 16
+       7.2.7.  The Submitter Element  . . . . . . . . . . . . . . . . 16
+       7.2.8.  The Owner Element  . . . . . . . . . . . . . . . . . . 16
+       7.2.9.  The Version Element  . . . . . . . . . . . . . . . . . 17
+       7.2.10. The Variable Element . . . . . . . . . . . . . . . . . 17
+     7.3.  Structure of Collation Registry  . . . . . . . . . . . . . 17
+     7.4.  Example Initial Registry Summary . . . . . . . . . . . . . 18
+
+
+
+Newman, et al.              Standards Track                     [Page 2]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   8.  Guidelines for Expert Reviewer . . . . . . . . . . . . . . . . 18
+   9.  Initial Collations . . . . . . . . . . . . . . . . . . . . . . 19
+     9.1.  ASCII Numeric Collation  . . . . . . . . . . . . . . . . . 20
+       9.1.1.  ASCII Numeric Collation Description  . . . . . . . . . 20
+       9.1.2.  ASCII Numeric Collation Registration . . . . . . . . . 20
+     9.2.  ASCII Casemap Collation  . . . . . . . . . . . . . . . . . 21
+       9.2.1.  ASCII Casemap Collation Description  . . . . . . . . . 21
+       9.2.2.  ASCII Casemap Collation Registration . . . . . . . . . 22
+     9.3.  Octet Collation  . . . . . . . . . . . . . . . . . . . . . 22
+       9.3.1.  Octet Collation Description  . . . . . . . . . . . . . 22
+       9.3.2.  Octet Collation Registration . . . . . . . . . . . . . 23
+   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 23
+   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 23
+   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
+   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
+     13.1. Normative References . . . . . . . . . . . . . . . . . . . 24
+     13.2. Informative References . . . . . . . . . . . . . . . . . . 24
+
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+Newman, et al.              Standards Track                     [Page 3]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+1.  Introduction
+
+   The Application Configuration Access Protocol ACAP [11] specification
+   introduced the concept of a comparator (which we call collation in
+   this document), but failed to create an IANA registry.  With the
+   introduction of stringprep [6] and the Unicode Collation Algorithm
+   [7], it is now time to create that registry and populate it with some
+   initial values appropriate for an international community.  This
+   specification replaces and generalizes the definition of a comparator
+   in ACAP, and creates a collation registry.
+
+1.1.  Conventions Used in This Document
+
+   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+   in this document are to be interpreted as defined in "Key words for
+   use in RFCs to Indicate Requirement Levels" [1].
+
+   The attribute syntax specifications use the Augmented Backus-Naur
+   Form (ABNF) [2] notation, including the core rules defined in
+   Appendix A.  The ABNF production "Language-tag" is imported from
+   Language Tags [5] and "reg-name" from URI: Generic Syntax [4].
+
+2.  Collation Definition and Purpose
+
+2.1.  Definition
+
+   A collation is a named function which takes two arbitrary length
+   strings as input and can be used to perform one or more of three
+   basic comparison operations: equality test, substring match, and
+   ordering test.
+
+2.2.  Purpose
+
+   Collations are an abstraction for comparison functions so that these
+   comparison functions can be used in multiple protocols.  The details
+   of a particular comparison operation can be specified by someone with
+   appropriate expertise, independent of the application protocols that
+   use that collation.  This is similar to the way a charset [13]
+   separates the details of octet to character mapping from a protocol
+   specification, such as MIME [9], or the way SASL [10] separates the
+   details of an authentication mechanism from a protocol specification,
+   such as ACAP [11].
+
+
+
+
+
+
+
+
+
+Newman, et al.              Standards Track                     [Page 4]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   Here is a small diagram to help illustrate the value of this
+   abstraction:
+
+   +-------------------+                         +-----------------+
+   | IMAP i18n SEARCH  |--+                      | Basic           |
+   +-------------------+  |                   +--| Collation Spec  |
+                          |                   |  +-----------------+
+   +-------------------+  |  +-------------+  |  +-----------------+
+   | ACAP i18n SEARCH  |--+--| Collation   |--+--| A stringprep    |
+   +-------------------+  |  | Registry    |  |  | Collation Spec  |
+                          |  +-------------+  |  +-----------------+
+   +-------------------+  |                   |  +-----------------+
+   | ...other protocol |--+                   |  | locale-specific |
+   +-------------------+                      +--| Collation Spec  |
+                                                 +-----------------+
+
+   Thus IMAP, ACAP, and future application protocols with international
+   search capability simply specify how to interface to the collation
+   registry instead of each protocol specification having to specify all
+   the collations it supports.
+
+2.3.  Some Other Terms Used in this Document
+
+   The terms client, server, and protocol are used in somewhat unusual
+   senses.
+
+   Client means a user, or a program acting directly on behalf of a
+   user.  This may be a mail reader acting as an IMAP client, or it may
+   be an interactive shell, where the user can type protocol commands/
+   requests directly, or it may be a script or program written by the
+   user.
+
+   Server means a program that performs services requested by the
+   client.  This may be a traditional server such as an HTTP server, or
+   it may be a Sieve [14] interpreter running a Sieve script written by
+   a user.  A server needs to use the operations provided by collations
+   in order to fulfill the client's requests.
+
+   The protocol describes how the client tells the server what it wants
+   done, and (if applicable) how the server tells the client about the
+   results.  IMAP is a protocol by this definition, and so is the Sieve
+   language.
+
+2.4.  Sort Keys
+
+   One component of a collation is a transformation, which turns a
+   string into a sort key, which is then used while sorting.
+
+
+
+
+Newman, et al.              Standards Track                     [Page 5]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   The transformation can range from an identity mapping (e.g., the
+   i;octet collation Section 9.3) to a mapping that makes the string
+   unreadable to a human.
+
+   This is an implementation detail of collations or servers.  A
+   protocol SHOULD NOT expose it to clients, since some collations leave
+   the sort key's format up to the implementation, and current
+   conformant implementations are known to use different formats.
+
+3.  Collation Identifier Syntax
+
+3.1.  Basic Syntax
+
+   The collation identifier itself is a single US-ASCII string.  The
+   identifier MUST NOT be longer than 254 characters, and obeys the
+   following grammar:
+
+     collation-char  = ALPHA / DIGIT / "-" / ";" / "=" / "."
+
+     collation-id    = collation-prefix ";" collation-core-name
+                       *collation-arg
+
+     collation-scope = Language-tag / "vnd-" reg-name
+
+     collation-core-name = ALPHA *( ALPHA / DIGIT / "-" )
+
+     collation-arg   = ";" ALPHA *( ALPHA / DIGIT ) "="
+                       1*( ALPHA / DIGIT / "." )
+
+
+   Note: the ABNF production "Language-tag" is imported from Language
+   Tags [5] and "reg-name" from URI: Generic Syntax [4].
+
+   There is a special identifier called "default".  For protocols that
+   have a default collation, "default" refers to that collation.  For
+   other protocols, the identifier "default" MUST match no collations,
+   and servers SHOULD treat it in the same way as they treat nonexistent
+   collations.
+
+3.2.  Wildcards
+
+   The string a client uses to select a collation MAY contain one or
+   more wildcard ("*") characters that match zero or more collation-
+   chars.  Wildcard characters MUST NOT be adjacent.  If the wildcard
+   string matches multiple collations, the server SHOULD attempt to
+   select a widely useful collation in preference to a narrowly useful
+   one.
+
+
+
+
+Newman, et al.              Standards Track                     [Page 6]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+     collation-wild  =  ("*" / (ALPHA ["*"])) *(collation-char ["*"])
+                         ; MUST NOT exceed 254 characters total
+
+3.3.  Ordering Direction
+
+   When used as a protocol element for ordering, the collation
+   identifier MAY be prefixed by either "+" or "-" to explicitly specify
+   an ordering direction. "+" has no effect on the ordering operation,
+   while "-" inverts the result of the ordering operation.  In general,
+   collation-order is used when a client requests a collation, and
+   collation-selected is used when the server informs the client of the
+   selected collation.
+
+     collation-selected =  ["+" / "-"] collation-id
+
+     collation-order =  ["+" / "-"] collation-wild
+
+3.4.  URIs
+
+   Some protocols are designed to use URIs [4] to refer to collations
+   rather than simple tokens.  A special section of the IANA URL space
+   is reserved for such usage.  The "collation-uri" form is used to
+   refer to a specific named collation (the collation registration may
+   not actually be present).  The "collation-auri" form is an abstract
+   name for an ordering, a collation pattern or a vendor private
+   collator.
+
+     collation-uri   =  "http://www.iana.org/assignments/collation/"
+                        collation-id ".xml"
+
+     collation-auri  =  ( "http://www.iana.org/assignments/collation/"
+                        collation-order ".xml" ) / other-uri
+
+     other-uri       =  <absoluteURI>
+                     ;  excluding the IANA collation namespace.
+
+3.5.  Naming Guidelines
+
+   While this specification makes no absolute requirements on the
+   structure of collation identifiers, naming consistency is important,
+   so the following initial guidelines are provided.
+
+   Collation identifiers with an international audience typically begin
+   with "i;".  Collation identifiers intended for a particular language
+   or locale typically begin with a language tag [5] followed by a ";".
+   After the first ";" is normally the name of the general collation
+   algorithm, followed by a series of algorithm modifications separated
+   by the ";" delimiter.  Parameterized modifications will use "=" to
+
+
+
+Newman, et al.              Standards Track                     [Page 7]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   delimit the parameter from the value.  The version numbers of any
+   lookup tables used by the algorithm SHOULD be present as
+   parameterized modifications.
+
+   Collation identifiers of the form *;vnd-hostname;* are reserved for
+   vendor-specific collations created by the owner of the hostname
+   following the "vnd-" prefix (e.g., vnd-example.com for the vendor
+   example.com).  Registration of such collations (or the name space as
+   a whole), with intended use of the "Vendor", is encouraged when a
+   public specification or open-source implementation is available, but
+   is not required.
+
+4.  Collation Specification Requirements
+
+4.1.  Collation/Server Interface
+
+   The collation itself defines what it operates on.  Most collations
+   are expected to operate on character strings.  The i;octet
+   (Section 9.3) collation operates on octet strings.  The i;ascii-
+   numeric (Section 9.1) operation operates on numbers.
+
+   This specification defines the collation interface in terms of octet
+   strings.  However, implementations may choose to use character
+   strings instead.  Such implementations may not be able to implement
+   e.g., i;octet.  Since i;octet is not currently mandatory to implement
+   for any protocol, this should not be a problem.
+
+4.2.  Operations Supported
+
+   A collation specification MUST state which of the three basic
+   operations are supported (equality, substring, ordering) and how to
+   perform each of the supported operations on any two input character
+   strings, including empty strings.  Collations must be deterministic,
+   i.e., given a collation with a specific identifier, and any two fixed
+   input strings, the result MUST be the same for the same operation.
+
+   In general, collation operations should behave as their names
+   suggest.  While a collation may be new, the operations are not, so
+   the new collation's operations should be similar to those of older
+   collations.  For example, a date/time collation should not provide a
+   "substring" operation that would morph IMAP substring SEARCH into
+   e.g., a date-range search.
+
+   A non-obvious consequence of the rules for each collation operation
+   is that, for any single collation, either none or all of the
+   operations can return "undefined".  For example, it is not possible
+   to have an equality operation that never returns "undefined", and a
+   substring operation that occasionally does.
+
+
+
+Newman, et al.              Standards Track                     [Page 8]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+4.2.1.  Validity
+
+   The validity test takes one string as argument.  It returns valid if
+   its input string is a valid input to the collation's other
+   operations, and invalid if not.  (In other words, a string is valid
+   if it is equal to itself according to the collation's equality
+   operation.)
+
+   The validity test is provided by all collations.  It MUST NOT be
+   listed separately in the collation registration.
+
+4.2.2.  Equality
+
+   The equality test always returns "match" or "no-match" when it is
+   supplied valid input, and MAY return "undefined" if one or both input
+   strings are not valid.
+
+   The equality test MUST be reflexive and symmetric.  For valid input,
+   it MUST be transitive.
+
+   If a collation provides either a substring or an ordering test, it
+   MUST also provide an equality test.  The substring and/or ordering
+   tests MUST be consistent with the equality test.
+
+   The return values of the equality test are called "match", "no-match"
+   and "undefined" in this document.
+
+4.2.3.  Substring
+
+   The substring matching operation determines if the first string is a
+   substring of the second string, i.e., if one or more substrings of
+   the second string is equal to the first, as defined by the
+   collation's equality operation.
+
+   A collation that supports substring matching will automatically
+   support two special cases of substring matching: prefix and suffix
+   matching, if those special cases are supported by the application
+   protocol.  It returns "match" or "no-match" when it is supplied valid
+   input and returns "undefined" when supplied invalid input.
+
+   Application protocols MAY return position information for substring
+   matches.  If this is done, the position information SHOULD include
+   both the starting offset and the ending offset for each match.  This
+   is important because more sophisticated collations can match strings
+   of unequal length (for example, a pre-composed accented character can
+   match a decomposed accented character).  In general, overlapping
+   matches SHOULD be reported (as when "ana" occurs twice within
+   "banana"), although there are cases where a collation may decide not
+
+
+
+Newman, et al.              Standards Track                     [Page 9]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   to.  For example, in a collation which treats all whitespace
+   sequences as identical, the substring operation could be defined such
+   that " 1 " (SP "1" SP) is reported just once within "  1  " (SP SP
+   "1" SP SP), not four times (SP SP "1" SP, SP "1" SP, SP "1" SP SP and
+   SP SP "1" SP SP), since the four matches are, in a sense, the same
+   match.
+
+   A string is a substring of itself.  The empty string is a substring
+   of all strings.
+
+   Note that the substring operation of some collations can match
+   strings of unequal length.  For example, a pre-composed accented
+   character can match a decomposed accented character.  The Unicode
+   Collation Algorithm [7] discusses this in more detail.
+
+   The return values of the substring operation are called "match", "no-
+   match", and "undefined" in this document.
+
+4.2.4.  Ordering
+
+   The ordering operation determines how two strings are ordered.  It
+   MUST be reflexive.  For valid input, it MUST be transitive and
+   trichotomous.
+
+   Ordering returns "less" if the first string is listed before the
+   second string, according to the collation; "greater", if the second
+   string is listed before the first string; and "equal", if the two
+   strings are equal, as defined by the collation's equality operation.
+   If one or both strings are invalid, the result of ordering is
+   "undefined".
+
+   When the collation is used with a "+" prefix, the behavior is the
+   same as when used with no prefix.  When the collation is used with a
+   "-" prefix, the result of the ordering operation of the collation
+   MUST be reversed.
+
+   The return values of the ordering operation are called "less",
+   "equal", "greater", and "undefined" in this document.
+
+4.3.  Sort Keys
+
+   A collation specification SHOULD describe the internal transformation
+   algorithm to generate sort keys.  This algorithm can be applied to
+   individual strings, and the result can be stored to potentially
+   optimize future comparison operations.  A collation MAY specify that
+   the sort key is generated by the identity function.  The sort key may
+   have no meaning to a human.  The sort key may not be valid input to
+   the collation.
+
+
+
+Newman, et al.              Standards Track                    [Page 10]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+4.4.  Use of Lookup Tables
+
+   Some collations use customizable lookup tables, e.g., because the
+   tables depend on locale, and may be modified after shipping the
+   software.  Collations that use more than one customizable lookup
+   table in a documented format MUST assign numbers to the tables they
+   use.  This permits an application protocol command to access the
+   tables used by a server collation, so that clients and servers use
+   the same tables.
+
+5.  Application Protocol Requirements
+
+   This section describes the requirements and issues that an
+   application protocol needs to consider if it offers searching,
+   substring matching and/or sorting, and permits the use of characters
+   outside the US-ASCII charset.
+
+5.1.  Character Encoding
+
+   The protocol specification has to make sure that it is clear on which
+   characters (rather than just octets) the collations are used.  This
+   can be done by specifying the protocol itself in terms of characters
+   (e.g., in the case of a query language), by specifying a single
+   character encoding for the protocol (e.g., UTF-8 [3]), or by
+   carefully describing the relevant issues of character encoding
+   labeling and conversion.  In the later case, details to consider
+   include how to handle unknown charsets, any charsets that are
+   mandatory-to-implement, any issues with byte-order that might apply,
+   and any transfer encodings that need to be supported.
+
+5.2.  Operations
+
+   The protocol must specify which of the operations defined in this
+   specification (equality matching, substring matching, and ordering)
+   can be invoked in the protocol, and how they are invoked.  There may
+   be more than one way to invoke an operation.
+
+   The protocol MUST provide a mechanism for the client to select the
+   collation to use with equality matching, substring matching, and
+   ordering.
+
+   If a protocol needs a total ordering and the collation chosen does
+   not provide it because the ordering operation returns "undefined" at
+   least once, the recommended fallback is to sort all invalid strings
+   after the valid ones, and use i;octet to order the invalid strings.
+
+   Although the collation's substring function provides a list of
+   matches, a protocol need not provide all that to the client.  It may
+
+
+
+Newman, et al.              Standards Track                    [Page 11]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   provide only the first matching substring, or even just the
+   information that the substring search matched.  In this way,
+   collations can be used with protocols that are defined such that "x
+   is a substring of y" returns true-false.
+
+   If the protocol provides positional information for the results of a
+   substring match, that positional information SHOULD fully specify the
+   substring(s) in the result that matches, independent of the length of
+   the search string.  For example, returning both the starting and
+   ending offset of the match would suffice, as would the starting
+   offset and a length.  Returning just the starting offset is not
+   acceptable.  This rule is necessary because advanced collations can
+   treat strings of different lengths as equal (for example, pre-
+   composed and decomposed accented characters).
+
+5.3.  Wildcards
+
+   The protocol MUST specify whether it allows the use of wildcards in
+   collation identifiers.  If the protocol allows wildcards, then:
+      The protocol MUST specify how comparisons behave in the absence of
+      explicit collation negotiation, or when a collation of "default"
+      is requested.  The protocol MAY specify that the default collation
+      used in such circumstances is sensitive to server configuration.
+
+      The protocol SHOULD provide a way to list available collations
+      matching a given wildcard pattern, or patterns.
+
+5.4.  String Comparison
+
+   If a protocol compares strings in any nontrivial way, using a
+   collation may be appropriate.  As an example, many protocols use
+   case-independent strings.  In many cases, a simple ASCII mapping to
+   upper/lower case works well.  In other cases, it may be better to use
+   a specifiable collation; for example, so that a server can treat "i"
+   and "I" as equivalent in Italy, and different in Turkey (Turkish also
+   has a dotted upper-case" I" and a dotless lower-case "i").
+
+   Protocol designers should consider, in each case, whether to use a
+   specifiable collation.  Keywords often have other needs than user
+   variables, and search arguments may be different again.
+
+5.5.  Disconnected Clients
+
+   If the protocol supports disconnected clients, and a collation is
+   used that can use configurable tables (e.g., to support
+   locale-specific extensions), then the client may not be able to
+   reproduce the server's collation operations while offline.
+
+
+
+
+Newman, et al.              Standards Track                    [Page 12]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   A mechanism to download such tables has been discussed.  Such a
+   mechanism is not included in the present specification, since the
+   problem is not yet well understood.
+
+5.6.  Error Codes
+
+   The protocol specification should consider assigning protocol error
+   codes for the following circumstances:
+
+   o  The client requests the use of a collation by identifier or
+      pattern, but no implemented collation matches that pattern.
+
+   o  The client attempts to use a collation for an operation that is
+      not supported by that collation -- for example, attempting to use
+      the "i;ascii-numeric" collation for substring matching.
+
+   o  The client uses an equality or substring matching collation, and
+      the result is an error.  It may be appropriate to distinguish
+      between the two input strings, particularly when one is supplied
+      by the client and the other is stored by the server.  It might
+      also be appropriate to distinguish the specific case of an invalid
+      UTF-8 string.
+
+5.7.  Octet Collation
+
+   The i;octet (Section 9.3) collation is only usable with protocols
+   based on octet-strings.  Clients and servers MUST NOT use i;octet
+   with other protocols.
+
+   If the protocol permits the use of collations with data structures
+   other than strings, the protocol MUST describe the default behavior
+   for a collation with those data structures.
+
+6.  Use by Existing Protocols
+
+   This section is informative.
+
+   Both ACAP [11] and Sieve [14] are standards track specifications that
+   used collations prior to the creation of this specification and
+   registry.  Those standards do not meet all the application protocol
+   requirements described in Section 5.
+
+   These protocols allow the use of the i;octet (Section 9.3) collation
+   working directly on UTF-8 data, as used in these protocols.
+
+
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 13]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   In Sieve, all matches are either true or false.  Accordingly, Sieve
+   servers must treat "undefined" and "no-match" results of the equality
+   and substring operations as false, and only "match" as true.
+
+   In ACAP and Sieve, there are no invalid strings.  In this document's
+   terms, invalid strings sort after valid strings.
+
+   IMAP [15] also collates, although that is explicit only when the
+   COMPARATOR [17] extension is used.  The built-in IMAP substring
+   operation and the ordering provided by the SORT [16] extension may
+   not meet the requirements made in this document.
+
+   Other protocols may be in a similar position.
+
+   In IMAP, the default collation is i;ascii-casemap, because its
+   operations are understood to match IMAP's built-in operations.
+
+7.  Collation Registration
+
+7.1.  Collation Registration Procedure
+
+   The IETF will create a mailing list, collation@ietf.org, which can be
+   used for public discussion of collation proposals prior to
+   registration.  Use of the mailing list is strongly encouraged.  The
+   IESG will appoint a designated expert who will monitor the
+   collation@ietf.org mailing list and review registrations.
+
+   The registration procedure begins when a completed registration
+   template is sent to iana@iana.org and collation@ietf.org.  The
+   designated expert is expected to tell IANA and the submitter of the
+   registration within two weeks whether the registration is approved,
+   approved with minor changes, or rejected with cause.  When a
+   registration is rejected with cause, it can be re-submitted if the
+   concerns listed in the cause are addressed.  Decisions made by the
+   designated expert can be appealed to the IESG Applications Area
+   Director, then to the IESG.  They follow the normal appeals procedure
+   for IESG decisions.
+
+   Collation registrations in a standards track, BCP, or IESG-approved
+   experimental RFC are owned by the IETF, and changes to the
+   registration follow normal procedures for updating such documents.
+   Collation registrations in other RFCs are owned by the RFC author(s).
+   Other collation registrations are owned by the individual(s) listed
+   in the contact field of the registration, and IANA will preserve this
+   information.
+
+   If the registration is a change of an existing collation, it MUST be
+   approved by the owner.  In the event the owner cannot be contacted
+
+
+
+Newman, et al.              Standards Track                    [Page 14]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   for a period of one month, and the designated expert deems the change
+   necessary, the IESG MAY re-assign ownership to an appropriate party.
+
+7.2.  Collation Registration Format
+
+   Registration of a collation is done by sending a well-formed XML
+   document to collation@ietf.org and iana@iana.org.
+
+7.2.1.  Registration Template
+
+   Here is a template for the registration:
+
+   <?xml version='1.0'?>
+   <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+   <collation rfc="YYYY" scope="global" intendedUse="common">
+     <identifier>collation identifier</identifier>
+     <title>technical title for collation</title>
+     <operations>equality order substring</operations>
+     <specification>specification reference</specification>
+     <owner>email address of owner or IETF</owner>
+     <submitter>email address of submitter</submitter>
+     <version>1</version>
+   </collation>
+
+7.2.2.  The Collation Element
+
+   The root of the registration document MUST be a <collation> element.
+   The collation element contains the other elements in the
+   registration, which are described in the following sub-subsections,
+   in the order given here.
+
+   The <collation> element MAY include an "rfc=" attribute if the
+   specification is in an RFC.  The "rfc=" attribute gives only the
+   number of the RFC, without any prefix, such as "RFC", or suffix, such
+   as ".txt".
+
+   The <collation> element MUST include a "scope=" attribute, which MUST
+   have one of the values "global", "local", or "other".
+
+   The <collation> element MUST include an "intendedUse=" attribute,
+   which must have one of the values "common", "limited", "vendor", or
+   "deprecated".  Collation specifications intended for "common" use are
+   expected to reference standards from standards bodies with
+   significant experience dealing with the details of international
+   character sets.
+
+   Be aware that future revisions of this specification may add
+   additional function types, as well as additional XML attributes,
+
+
+
+Newman, et al.              Standards Track                    [Page 15]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   values, and elements.  Any system that automatically parses these XML
+   documents MUST take this into account to preserve future
+   compatibility.
+
+7.2.3.  The Identifier Element
+
+   The <identifier> element gives the precise identifier of the
+   collation, e.g., i;ascii-casemap.  The <identifier> element is
+   mandatory.
+
+7.2.4.  The Title Element
+
+   The <title> element gives the title of the collation.  The <title>
+   element is mandatory.
+
+7.2.5.  The Operations Element
+
+   The <operations> element lists which of the three operations
+   ("equality", "order" or "substring") the collation provides,
+   separated by single spaces.  The <operations> element is mandatory.
+
+7.2.6.  The Specification Element
+
+   The <specification> element describes where to find the
+   specification.  The <specification> element is mandatory.  It MAY
+   have a URI attribute.  There may be more than one <specification>
+   element, in which case, they together form the specification.
+
+   If it is discovered that parts of a collation specification conflict,
+   a new revision of the collation is necessary, and the
+   collation@ietf.org mailing list should be notified.
+
+7.2.7.  The Submitter Element
+
+   The <submitter> element provides an RFC 2822 [12] email address for
+   the person who submitted the registration.  It is optional if the
+   <owner> element contains an email address.
+
+   There may be more than one <submitter> element.
+
+7.2.8.  The Owner Element
+
+   The <owner> element contains either the four letters "IETF" or an
+   email address of the owner of the registration.  The <owner> element
+   is mandatory.  There may be more than one <owner> element.  If so,
+   all owners are equal.  Each owner can speak for all.
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 16]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+7.2.9.  The Version Element
+
+   The <version> element MUST be included when the registration is
+   likely to be revised, or has been revised in such a way that the
+   results change for one or more input strings.  The <version> element
+   is optional.
+
+7.2.10.  The Variable Element
+
+   The <variable> element specifies an optional variable to control the
+   collation's behaviour, for example whether it is case sensitive.  The
+   <variable> element is optional.  When <variable> is used, it must
+   contain <name> and <default> elements, and it may contain one or more
+   <value> elements.
+
+7.2.10.1.  The Name Element
+
+   The <name> element specifies the name value of a variable.  The
+   <name> element is mandatory.
+
+7.2.10.2.  The Default Element
+
+   The <default> element specifies the default value of a variable.  The
+   <default> element is mandatory.
+
+7.2.10.3.  The Value Element
+
+   The <value> element specifies a legal value of a variable.  The
+   <value> element is optional.  If one or more <value> elements are
+   present, only those values are legal.  If none are, then the
+   variable's legal values do not form an enumerated set, and the rules
+   MUST be specified in an RFC accompanying the registration.
+
+7.3.  Structure of Collation Registry
+
+   Once the registration is approved, IANA will store each XML
+   registration document in a URL of the form
+   http://www.iana.org/assignments/collation/collation-id.xml, where
+   collation-id is the content of the identifier element in the
+   registration.  Both the submitter and the designated expert are
+   responsible for verifying that the XML is well-formed.  The
+   registration document should avoid using new elements.  If any are
+   necessary, it is important to be consistent with other registrations.
+
+   IANA will also maintain a text summary of the registry under the name
+   http://www.iana.org/assignments/collation/collation-index.html.  This
+   summary is divided into four sections.  The first section is for
+   collations intended for common use.  This section is intended for
+
+
+
+Newman, et al.              Standards Track                    [Page 17]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   collation registrations published in IESG-approved RFCs, or for
+   locally scoped collations from the primary standards body for that
+   locale.  The designated expert is encouraged to reject collation
+   registrations with an intended use of "common" if the expert believes
+   it should be "limited", as it is desirable to keep the number of
+   "common" registrations small and of high quality.  The second section
+   is reserved for limited-use collations.  The third section is
+   reserved for registered vendor-specific collations.  The final
+   section is reserved for deprecated collations.
+
+7.4.  Example Initial Registry Summary
+
+   The following is an example of how IANA might structure the initial
+   registry summary.html file:
+
+     Collation                              Functions Scope Reference
+     ---------                              --------- ----- ---------
+   Common Use Collations:
+     i;ascii-casemap                        e, o, s   Local [RFC 4790]
+
+   Limited Use Collations:
+     i;octet                                e, o, s   Other [RFC 4790]
+     i;ascii-numeric                        e, o      Other [RFC 4790]
+
+   Vendor Collations:
+
+   Deprecated Collations:
+
+
+   References
+   ----------
+   [RFC 4790]  Newman, C., Duerst, M., Gulbrandsen, A., "Internet
+               Application Protocol Collation Registry", RFC 4790,
+               Sun Microsystems, March 2007.
+
+8.  Guidelines for Expert Reviewer
+
+   The expert reviewer appointed by the IESG has fairly broad latitude
+   for this registry.  While a number of collations are expected
+   (particularly customizations of the UCA for localized use), an
+   explosion of collations (particularly common-use collations) is not
+   desirable for widespread interoperability.  However, it is important
+   for the expert reviewer to provide cause when rejecting a
+   registration, and, when possible, to describe corrective action to
+
+
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 18]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   permit the registration to proceed.  The following table includes
+   some example reasons to reject a registration with cause:
+
+   o  The registration is not a well-formed XML document.
+
+   o  The registration has an intended use of "common", but there is no
+      evidence the collation will be widely deployed, so it should be
+      listed as "limited".
+
+   o  The registration has an intended use of "common", but it is
+      redundant with the functionality of a previously registered
+      "common" collation.
+
+   o  The registration has an intended use of "common", but the
+      specification is not detailed enough to allow interoperable
+      implementations by others.
+
+   o  The collation identifier fails to precisely identify the version
+      numbers of relevant tables to use.
+
+   o  The registration fails to meet one of the "MUST" requirements in
+      Section 4.
+
+   o  The collation identifier fails to meet the syntax in Section 3.
+
+   o  The collation specification referenced in the registration is
+      vague or has optional features without a clear behavior specified.
+
+   o  The referenced specification does not adequately address security
+      considerations specific to that collation.
+
+   o  The registration's operations are needlessly different from those
+      of traditional operations.
+
+   o  The registration's XML is needlessly different from that of
+      already registered collations.
+
+9.  Initial Collations
+
+   This section registers the three collations that were originally
+   defined in [11], and are implemented in most [14] engines.  Some of
+   the behavior of these collations is perhaps not ideal, such as
+   i;ascii-casemap accepting non-ASCII input.  Compatibility with widely
+   deployed code was judged more important than fixing the collations.
+   Some of the aspects of these collations are necessary to maintain
+   compatibility with widely deployed code.
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 19]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+9.1.  ASCII Numeric Collation
+
+9.1.1.  ASCII Numeric Collation Description
+
+   The "i;ascii-numeric" collation is a simple collation intended for
+   use with arbitrarily-sized, unsigned decimal integer numbers stored
+   as octet strings.  US-ASCII digits (0x30 to 0x39) represent digits of
+   the numbers.  Before converting from string to integer, the input
+   string is truncated at the first non-digit character.  All input is
+   valid; strings that do not start with a digit represent positive
+   infinity.
+
+   The collation supports equality and ordering, but does not support
+   the substring operation.
+
+   The equality operation returns "match" if the two strings represent
+   the same number (i.e., leading zeroes and trailing non-digits are
+   disregarded), and "no-match" if the two strings represent different
+   numbers.
+
+   The ordering operation returns "less" if the first string represents
+   a smaller number than the second, "equal" if they represent the same
+   number, and "greater" if the first string represents a larger number
+   than the second.
+
+   Some examples: "0" is less than "1", and "1" is less than
+   "4294967298". "4294967298", "04294967298", and "4294967298b" are all
+   equal. "04294967298" is less than "". "", "x", and "y" are equal.
+
+9.1.2.  ASCII Numeric Collation Registration
+
+   <?xml version='1.0'?>
+   <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+   <collation rfc="4790" scope="other" intendedUse="limited">
+     <identifier>i;ascii-numeric</identifier>
+     <title>ASCII Numeric</title>
+     <operations>equality order</operations>
+     <specification>RFC 4790</specification>
+     <owner>IETF</owner>
+     <submitter>chris.newman@sun.com</submitter>
+   </collation>
+
+
+
+
+
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 20]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+9.2.  ASCII Casemap Collation
+
+9.2.1.  ASCII Casemap Collation Description
+
+   The "i;ascii-casemap" collation is a simple collation that operates
+   on octet strings and treats US-ASCII letters case-insensitively.  It
+   provides equality, substring, and ordering operations.  All input is
+   valid.  Note that letters outside ASCII are not treated case-
+   insensitively.
+
+   Its equality, ordering, and substring operations are as for i;octet,
+   except that at first, the lower-case letters (octet values 97-122) in
+   each input string are changed to upper case (octet values 65-90).
+
+   Care should be taken when using OS-supplied functions to implement
+   this collation, as it is not locale sensitive.  Functions, such as
+   strcasecmp and toupper, are sometimes locale sensitive, and may
+   inappropriately map lower-case letters other than a-z to upper case.
+
+   The i;ascii-casemap collation is well-suited for use with many
+   Internet protocols and computer languages.  Use with natural language
+   is often inappropriate; even though the collation apparently supports
+   languages such as Swahili and English, in real-world use, it tends to
+   mis-sort a number of types of string:
+
+   o  people and place names containing non-ASCII,
+
+   o  words such as "naive" (if spelled with an accent, the accented
+      character could push the word to the wrong spot in a sorted list),
+
+   o  names such as "Lloyd" (which, in Welsh, sorts after "Lyon", unlike
+      in English),
+
+   o  strings containing euro and pound sterling symbols, quotation
+      marks other than '"', dashes/hyphens, etc.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 21]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+9.2.2.  ASCII Casemap Collation Registration
+
+   <?xml version='1.0'?>
+   <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+   <collation rfc="4790" scope="local" intendedUse="common">
+     <identifier>i;ascii-casemap</identifier>
+     <title>ASCII Casemap</title>
+     <operations>equality order substring</operations>
+     <specification>RFC 4790</specification>
+     <owner>IETF</owner>
+     <submitter>chris.newman@sun.com</submitter>
+   </collation>
+
+9.3.  Octet Collation
+
+9.3.1.  Octet Collation Description
+
+   The "i;octet" collation is a simple and fast collation intended for
+   use on binary octet strings rather than on character data.  Protocols
+   that want to make this collation available have to do so by
+   explicitly allowing it.  If not explicitly allowed, it MUST NOT be
+   used.  It never returns an "undefined" result.  It provides equality,
+   substring, and ordering operations.
+
+   The ordering algorithm is as follows:
+
+   1.  If both strings are the empty string, return the result "equal".
+
+   2.  If the first string is empty and the second is not, return the
+       result "less".
+
+   3.  If the second string is empty and the first is not, return the
+       result "greater".
+
+   4.  If both strings begin with the same octet value, remove the first
+       octet from both strings and repeat this algorithm from step 1.
+
+   5.  If the unsigned value (0 to 255) of the first octet of the first
+       string is less than the unsigned value of the first octet of the
+       second string, then return "less".
+
+   6.  If this step is reached, return "greater".
+
+   This algorithm is roughly equivalent to the C library function
+   memcmp, with appropriate length checks added.
+
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 22]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   The matching operation returns "match" if the sorting algorithm would
+   return "equal".  Otherwise, the matching operation returns "no-
+   match".
+
+   The substring operation returns "match" if the first string is the
+   empty string, or if there exists a substring of the second string of
+   length equal to the length of the first string, which would result in
+   a "match" result from the equality function.  Otherwise, the
+   substring operation returns "no-match".
+
+9.3.2.  Octet Collation Registration
+
+   This collation is defined with intendedUse="limited" because it can
+   only be used by protocols that explicitly allow it.
+
+   <?xml version='1.0'?>
+   <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+   <collation rfc="4790" scope="global" intendedUse="limited">
+     <identifier>i;octet</identifier>
+     <title>Octet</title>
+     <operations>equality order substring</operations>
+     <specification>RFC 4790</specification>
+     <owner>IETF</owner>
+     <submitter>chris.newman@sun.com</submitter>
+   </collation>
+
+10.  IANA Considerations
+
+   Section 7 defines how to register collations with IANA.  Section 9
+   defines a list of predefined collations that have been registered
+   with IANA.
+
+11.  Security Considerations
+
+   Collations will normally be used with UTF-8 strings.  Thus, the
+   security considerations for UTF-8 [3], stringprep [6], and Unicode
+   TR-36 [8] also apply, and are normative to this specification.
+
+12.  Acknowledgements
+
+   The authors want to thank all who have contributed to this document,
+   including Brian Carpenter, John Cowan, Dave Cridland, Mark Davis,
+   Spencer Dawkins, Lisa Dusseault, Lars Eggert, Frank Ellermann, Philip
+   Guenther, Tony Hansen, Ted Hardie, Sam Hartman, Kjetil Torgrim Homme,
+   Michael Kay, John Klensin, Alexey Melnikov, Jim Melton, and Abhijit
+   Menon-Sen.
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 23]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+13.  References
+
+13.1.  Normative References
+
+   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
+         Levels", BCP 14, RFC 2119, March 1997.
+
+   [2]   Crocker, D. and P. Overell, "Augmented BNF for Syntax
+         Specifications: ABNF", RFC 4234, October 2005.
+
+   [3]   Yergeau, F., "UTF-8, a transformation format of ISO 10646",
+         STD 63, RFC 3629, November 2003.
+
+   [4]   Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
+         Resource Identifier (URI): Generic Syntax", RFC 3986,
+         January 2005.
+
+   [5]   Phillips, A. and M. Davis, "Tags for Identifying Languages",
+         BCP 47, RFC 4646, September 2006.
+
+   [6]   Hoffman, P. and M. Blanchet, "Preparation of Internationalized
+         Strings ("stringprep")", RFC 3454, December 2002.
+
+   [7]   Davis, M. and K. Whistler, "Unicode Collation Algorithm version
+         14", May 2005,
+         <http://www.unicode.org/reports/tr10/tr10-14.html>.
+
+   [8]   Davis, M. and M. Suignard, "Unicode Security Considerations",
+         February 2006, <http://www.unicode.org/reports/tr36/>.
+
+13.2.  Informative References
+
+   [9]   Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+         Extensions (MIME) Part One: Format of Internet Message Bodies",
+         RFC 2045, November 1996.
+
+   [10]  Melnikov, A., "Simple Authentication and Security Layer
+         (SASL)", RFC 4422, June 2006.
+
+   [11]  Newman, C. and J. Myers, "ACAP -- Application Configuration
+         Access Protocol", RFC 2244, November 1997.
+
+   [12]  Resnick, P., "Internet Message Format", RFC 2822, April 2001.
+
+   [13]  Freed, N. and J. Postel, "IANA Charset Registration
+         Procedures", BCP 19, RFC 2978, October 2000.
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 24]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+   [14]  Showalter, T., "Sieve: A Mail Filtering Language", RFC 3028,
+         January 2001.
+
+   [15]  Crispin, M., "Internet Message Access Protocol - Version
+         4rev1", RFC 3501, March 2003.
+
+   [16]  Crispin, M. and K. Murchison, "Internet Message Access Protocol
+         - Sort and Thread Extensions", Work in Progress, May 2004.
+
+   [17]  Newman, C. and A. Gulbrandsen, "Internet Message Access
+         Protocol Internationalization", Work in Progress, January 2006.
+
+Authors' Addresses
+
+   Chris Newman
+   Sun Microsystems
+   1050 Lakes Drive
+   West Covina, CA  91790
+   USA
+
+   EMail: chris.newman@sun.com
+
+
+   Martin Duerst
+   Aoyama Gakuin University
+   5-10-1 Fuchinobe
+   Sagamihara, Kanagawa  229-8558
+   Japan
+
+   Phone: +81 42 759 6329
+   Fax:   +81 42 759 6495
+   EMail: duerst@it.aoyama.ac.jp
+   URI:   http://www.sw.it.aoyama.ac.jp/D%C3%BCrst/
+
+   Note: Please write "Duerst" with u-umlaut wherever possible, for
+   example as "D&#252;rst" in XML and HTML.
+
+
+   Arnt Gulbrandsen
+   Oryx Mail Systems GmbH
+   Schweppermannstr. 8
+   81671 Munich
+   Germany
+
+   Fax:   +49 89 4502 9758
+   EMail: arnt@oryx.com
+   URI:   http://www.oryx.com/arnt/
+
+
+
+
+Newman, et al.              Standards Track                    [Page 25]
+
+RFC 4790                   Collation Registry                 March 2007
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2007).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+Newman, et al.              Standards Track                    [Page 26]
+
diff --git a/imap/docs/rfc/rfc4959.txt b/imap/docs/rfc/rfc4959.txt
new file mode 100644
index 00000000..3df18354
--- /dev/null
+++ b/imap/docs/rfc/rfc4959.txt
@@ -0,0 +1,395 @@
+
+
+
+
+
+
+Network Working Group                                      R. Siemborski
+Request for Comments: 4959                                  Google, Inc.
+Category: Standards Track                                 A. Gulbrandsen
+                                                  Oryx Mail Systems GmbH
+                                                          September 2007
+
+
+   IMAP Extension for Simple Authentication and Security Layer (SASL)
+                        Initial Client Response
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   To date, the Internet Message Access Protocol (IMAP) has used a
+   Simple Authentication and Security Layer (SASL) profile which always
+   required at least one complete round trip for an authentication, as
+   it did not support an initial client response argument.  This
+   additional round trip at the beginning of the session is undesirable,
+   especially when round-trip costs are high.
+
+   This document defines an extension to IMAP which allows clients and
+   servers to avoid this round trip by allowing an initial client
+   response argument to the IMAP AUTHENTICATE command.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski & Gulbrandsen  Standards Track                       [Page 1]
+
+RFC 4959       IMAP Ext for SASL Initial Client Response  September 2007
+
+
+1.  Introduction
+
+   The SASL initial client response extension is present in any IMAP
+   [RFC3501] server implementation which returns "SASL-IR" as one of the
+   supported capabilities in its CAPABILITY response.
+
+   Servers which support this extension will accept an optional initial
+   client response with the AUTHENTICATE command for any SASL [RFC4422]
+   mechanisms which support it.
+
+2.  Conventions Used in This Document
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC2119].
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.
+
+   Formal syntax is defined by [RFC4234] as extended by [RFC3501].
+
+3.  IMAP Changes to the IMAP AUTHENTICATE Command
+
+   This extension adds an optional second argument to the AUTHENTICATE
+   command that is defined in Section 6.2.2 of [RFC3501].  If this
+   second argument is present, it represents the contents of the
+   "initial client response" defined in Section 5.1 of [RFC4422].
+
+   As with any other client response, this initial client response MUST
+   be encoded as defined in Section 4 of [RFC4648].  It also MUST be
+   transmitted outside of a quoted string or literal.  To send a zero-
+   length initial response, the client MUST send a single pad character
+   ("=").  This indicates that the response is present, but is a zero-
+   length string.
+
+   When decoding the BASE64 [RFC4648] data in the initial client
+   response, decoding errors MUST be treated as IMAP [RFC3501] would
+   handle them in any normal SASL client response.  In particular, the
+   server should check for any characters not explicitly allowed by the
+   BASE64 alphabet, as well as any sequence of BASE64 characters that
+   contains the pad character ('=') anywhere other than the end of the
+   string (e.g., "=AAA" and "AAA=BBB" are not allowed).
+
+   If the client uses an initial response with a SASL mechanism that
+   does not support an initial response, the server MUST reject the
+   command with a tagged BAD response.
+
+
+
+
+
+Siemborski & Gulbrandsen  Standards Track                       [Page 2]
+
+RFC 4959       IMAP Ext for SASL Initial Client Response  September 2007
+
+
+   Note: support and use of the initial client response is optional for
+   both clients and servers.  Servers that implement this extension MUST
+   support clients that omit the initial client response, and clients
+   that implement this extension MUST NOT send an initial client
+   response to servers that do not advertise the SASL-IR capability.  In
+   such a situation, clients MUST fall back to an IMAP [RFC3501]
+   compatible mode.
+
+   If either the client or the server do not support the SASL-IR
+   capability, a mechanism which uses an initial client response is
+   negotiated using the challenge/response exchange described in
+   [RFC3501], with an initial zero-length server challenge.
+
+4.  Examples
+
+   The following is an example authentication using the PLAIN (see
+   [RFC4616]) SASL mechanism (under a TLS protection layer, see
+   [RFC4346]) and an initial client response:
+
+            ... client connects to server and negotiates a TLS
+           protection layer ...
+        C: C01 CAPABILITY
+        S: * CAPABILITY IMAP4rev1 SASL-IR AUTH=PLAIN
+        S: C01 OK Completed
+        C: A01 AUTHENTICATE PLAIN dGVzdAB0ZXN0AHRlc3Q=
+        S: A01 OK Success (tls protection)
+
+   Note that even when a server supports this extension, the following
+   negotiation (which does not use the initial response) is still valid
+   and MUST be supported by the server:
+
+            ... client connects to server and negotiates a TLS
+           protection layer ...
+        C: C01 CAPABILITY
+        S: * CAPABILITY IMAP4rev1 SASL-IR AUTH=PLAIN
+        S: C01 OK Completed
+        C: A01 AUTHENTICATE PLAIN
+            (note that there is a space following the "+" in the
+           following line)
+        S: +
+        C: dGVzdAB0ZXN0AHRlc3Q=
+        S: A01 OK Success (tls protection)
+
+   The following is an example authentication using the SASL EXTERNAL
+   mechanism (defined in [RFC4422]) under a TLS protection layer (see
+   [RFC4346]) and an empty initial client response:
+
+
+
+
+
+Siemborski & Gulbrandsen  Standards Track                       [Page 3]
+
+RFC 4959       IMAP Ext for SASL Initial Client Response  September 2007
+
+
+            ... client connects to server and negotiates a TLS
+           protection layer ...
+        C: C01 CAPABILITY
+        S: * CAPABILITY IMAP4rev1 SASL-IR AUTH=PLAIN AUTH=EXTERNAL
+        S: C01 OK Completed
+        C: A01 AUTHENTICATE EXTERNAL =
+        S: A01 OK Success (tls protection)
+
+   This is in contrast with the handling of such a situation when an
+   initial response is omitted:
+
+         ... client connects to server and negotiates a TLS protection
+           layer ...
+        C: C01 CAPABILITY
+        S: * CAPABILITY IMAP4rev1 SASL-IR AUTH=PLAIN AUTH=EXTERNAL
+        S: C01 OK Completed
+        C: A01 AUTHENTICATE EXTERNAL
+            (note that there is a space following the "+" in the
+           following line)
+        S: +
+        C:
+        S: A01 OK Success (tls protection)
+
+5.  IANA Considerations
+
+   The IANA has added SASL-IR to the IMAP4 Capabilities Registry.
+
+6.  Security Considerations
+
+   The extension defined in this document is subject to many of the
+   Security Considerations defined in [RFC3501] and [RFC4422].
+
+   Server implementations MUST treat the omission of an initial client
+   response from the AUTHENTICATE command as defined by [RFC3501] (as if
+   this extension did not exist).
+
+   Although [RFC3501] has no express line length limitations, some
+   implementations choose to enforce them anyway.  Such implementations
+   MUST be aware that the addition of the initial response parameter to
+   AUTHENTICATE may increase the maximum line length that IMAP parsers
+   may expect to support.  Server implementations MUST be able to
+   receive the largest possible initial client response that their
+   supported mechanisms might receive.
+
+
+
+
+
+
+
+
+Siemborski & Gulbrandsen  Standards Track                       [Page 4]
+
+RFC 4959       IMAP Ext for SASL Initial Client Response  September 2007
+
+
+7.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form [RFC4234] notation.  [RFC3501] defines the non-terminals
+   capability, auth-type, and base64.
+
+      capability    =/ "SASL-IR"
+
+      authenticate  = "AUTHENTICATE" SP auth-type [SP (base64 / "=")]
+                      *(CRLF base64)
+                      ;;redefine AUTHENTICATE from [RFC3501]
+
+8.  Acknowledgments
+
+   The authors would like to acknowledge the contributions of Ken
+   Murchison and Mark Crispin, along with the rest of the IMAPEXT
+   Working Group for their assistance in reviewing this document.
+
+   Alexey Melnikov and Cyrus Daboo also had some early discussions about
+   this extension.
+
+9.  References
+
+9.1.  Normative References
+
+   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC3501]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+              4rev1", RFC 3501, March 2003.
+
+   [RFC4234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
+              Specifications: ABNF", RFC 4234, October 2005.
+
+   [RFC4422]  Melnikov, A. and  K. Zeilenga, "Simple Authentication and
+              Security Layer (SASL)", RFC 4422, June 2006.
+
+   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
+              Encodings", RFC 4648, October 2006.
+
+9.2.  Informative References
+
+   [RFC4616]  Zeilenga, K., "The PLAIN Simple Authentication and
+              Security Layer (SASL) Mechanism", RFC 4616, August 2006.
+
+   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
+              (TLS) Protocol Version 1.1", RFC 4346, April 2006.
+
+
+
+
+Siemborski & Gulbrandsen  Standards Track                       [Page 5]
+
+RFC 4959       IMAP Ext for SASL Initial Client Response  September 2007
+
+
+Authors' Addresses
+
+   Robert Siemborski
+   Google, Inc.
+   1600 Ampitheatre Parkway
+   Mountain View, CA 94043
+
+   Phone: +1 650 623 6925
+   EMail: robsiemb@google.com
+
+
+   Arnt Gulbrandsen
+   Oryx Mail Systems GmbH
+   Schweppermannstr. 8
+   D-81671 Muenchen
+   Germany
+
+   EMail: arnt@oryx.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski & Gulbrandsen  Standards Track                       [Page 6]
+
+RFC 4959       IMAP Ext for SASL Initial Client Response  September 2007
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2007).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski & Gulbrandsen  Standards Track                       [Page 7]
+
diff --git a/imap/docs/rfc/rfc4978.txt b/imap/docs/rfc/rfc4978.txt
new file mode 100644
index 00000000..14b56b6e
--- /dev/null
+++ b/imap/docs/rfc/rfc4978.txt
@@ -0,0 +1,507 @@
+
+
+
+
+
+
+Network Working Group                                     A. Gulbrandsen
+Request for Comments: 4978                        Oryx Mail Systems GmbH
+Category: Standards Track                                    August 2007
+
+
+                      The IMAP COMPRESS Extension
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   The COMPRESS extension allows an IMAP connection to be effectively
+   and efficiently compressed.
+
+   Table of Contents
+
+   1. Introduction and Overview .......................................2
+   2. Conventions Used in This Document ...............................2
+   3. The COMPRESS Command ............................................3
+   4. Compression Efficiency ..........................................4
+   5. Formal Syntax ...................................................6
+   6. Security Considerations .........................................6
+   7. IANA Considerations .............................................6
+   8. Acknowledgements ................................................7
+   9. References ......................................................7
+      9.1. Normative References .......................................7
+      9.2. Informative References .....................................7
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen                 Standards Track                     [Page 1]
+
+RFC 4978              The IMAP COMPRESS Extension            August 2007
+
+
+1.  Introduction and Overview
+
+   A server which supports the COMPRESS extension indicates this with
+   one or more capability names consisting of "COMPRESS=" followed by a
+   supported compression algorithm name as described in this document.
+
+   The goal of COMPRESS is to reduce the bandwidth usage of IMAP.
+
+   Compared to PPP compression (see [RFC1962]) and modem-based
+   compression (see [MNP] and [V42BIS]), COMPRESS offers much better
+   compression efficiency.  COMPRESS can be used together with Transport
+   Security Layer (TLS) [RFC4346], Simple Authentication and Security
+   layer (SASL) encryption, Virtual Private Networks (VPNs), etc.
+   Compared to TLS compression [RFC3749], COMPRESS has the following
+   (dis)advantages:
+
+   - COMPRESS can be implemented easily both by IMAP servers and
+     clients.
+
+   - IMAP COMPRESS benefits from an intimate knowledge of the IMAP
+     protocol's state machine, allowing for dynamic and aggressive
+     optimization of the underlying compression algorithm's parameters.
+
+   - When the TLS layer implements compression, any protocol using that
+     layer can transparently benefit from that compression (e.g., SMTP
+     and IMAP).  COMPRESS is specific to IMAP.
+
+   In order to increase interoperation, it is desirable to have as few
+   different compression algorithms as possible, so this document
+   specifies only one.  The DEFLATE algorithm (defined in [RFC1951]) is
+   standard, widely available and fairly efficient, so it is the only
+   algorithm defined by this document.
+
+   In order to increase interoperation, IMAP servers that advertise this
+   extension SHOULD also advertise the TLS DEFLATE compression mechanism
+   as defined in [RFC3749].  IMAP clients MAY use either COMPRESS or TLS
+   compression, however, if the client and server support both, it is
+   RECOMMENDED that the client choose TLS compression.
+
+   The extension adds one new command (COMPRESS) and no new responses.
+
+2.  Conventions Used in This Document
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC2119].
+
+   Formal syntax is defined by [RFC4234] as modified by [RFC3501].
+
+
+
+Gulbrandsen                 Standards Track                     [Page 2]
+
+RFC 4978              The IMAP COMPRESS Extension            August 2007
+
+
+   In the examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively. "[...]" denotes elision.
+
+3.  The COMPRESS Command
+
+   Arguments: Name of compression mechanism: "DEFLATE".
+
+   Responses: None
+
+   Result: OK The server will compress its responses and expects the
+              client to compress its commands.
+           NO Compression is already active via another layer.
+          BAD Command unknown, invalid or unknown argument, or COMPRESS
+              already active.
+
+   The COMPRESS command instructs the server to use the named
+   compression mechanism ("DEFLATE" is the only one defined) for all
+   commands and/or responses after COMPRESS.
+
+   The client MUST NOT send any further commands until it has seen the
+   result of COMPRESS.  If the response was OK, the client MUST compress
+   starting with the first command after COMPRESS.  If the server
+   response was BAD or NO, the client MUST NOT turn on compression.
+
+   If the server responds NO because it knows that the same mechanism is
+   active already (e.g., because TLS has negotiated the same mechanism),
+   it MUST send COMPRESSIONACTIVE as resp-text-code (see [RFC3501],
+   Section 7.1), and the resp-text SHOULD say which layer compresses.
+
+   If the server issues an OK response, the server MUST compress
+   starting immediately after the CRLF which ends the tagged OK
+   response.  (Responses issued by the server before the OK response
+   will, of course, still be uncompressed.)  If the server issues a BAD
+   or NO response, the server MUST NOT turn on compression.
+
+   For DEFLATE (as for many other compression mechanisms), the
+   compressor can trade speed against quality.  When decompressing there
+   isn't much of a tradeoff.  Consequently, the client and server are
+   both free to pick the best reasonable rate of compression for the
+   data they send.
+
+   When COMPRESS is combined with TLS (see [RFC4346]) or SASL (see
+   [RFC4422]) security layers, the sending order of the three extensions
+   MUST be first COMPRESS, then SASL, and finally TLS.  That is, before
+   data is transmitted it is first compressed.  Second, if a SASL
+   security layer has been negotiated, the compressed data is then
+   signed and/or encrypted accordingly.  Third, if a TLS security layer
+   has been negotiated, the data from the previous step is signed and/or
+
+
+
+Gulbrandsen                 Standards Track                     [Page 3]
+
+RFC 4978              The IMAP COMPRESS Extension            August 2007
+
+
+   encrypted accordingly.  When receiving data, the processing order
+   MUST be reversed.  This ensures that before sending, data is
+   compressed before it is encrypted, independent of the order in which
+   the client issues COMPRESS, AUTHENTICATE, and STARTTLS.
+
+   The following example illustrates how commands and responses are
+   compressed during a simple login sequence:
+
+        S: * OK [CAPABILITY IMAP4REV1 STARTTLS COMPRESS=DEFLATE]
+        C: a starttls
+        S: a OK TLS active
+
+            From this point on, everything is encrypted.
+
+        C: b login arnt tnra
+        S: b OK Logged in as arnt
+        C: c compress deflate
+        S: d OK DEFLATE active
+
+            From this point on, everything is compressed before being
+            encrypted.
+
+   The following example demonstrates how a server may refuse to
+   compress twice:
+
+        S: * OK [CAPABILITY IMAP4REV1 STARTTLS COMPRESS=DEFLATE]
+        [...]
+        C: c compress deflate
+        S: c NO [COMPRESSIONACTIVE] DEFLATE active via TLS
+
+4.  Compression Efficiency
+
+   This section is informative, not normative.
+
+   IMAP poses some unusual problems for a compression layer.
+
+   Upstream is fairly simple.  Most IMAP clients send the same few
+   commands again and again, so any compression algorithm that can
+   exploit repetition works efficiently.  The APPEND command is an
+   exception; clients that send many APPEND commands may want to
+   surround large literals with flushes in the same way as is
+   recommended for servers later in this section.
+
+   Downstream has the unusual property that several kinds of data are
+   sent, confusing all dictionary-based compression algorithms.
+
+
+
+
+
+
+Gulbrandsen                 Standards Track                     [Page 4]
+
+RFC 4978              The IMAP COMPRESS Extension            August 2007
+
+
+   One type is IMAP responses.  These are highly compressible; zlib
+   using its least CPU-intensive setting compresses typical responses to
+   25-40% of their original size.
+
+   Another type is email headers.  These are equally compressible, and
+   benefit from using the same dictionary as the IMAP responses.
+
+   A third type is email body text.  Text is usually fairly short and
+   includes much ASCII, so the same compression dictionary will do a
+   good job here, too.  When multiple messages in the same thread are
+   read at the same time, quoted lines etc. can often be compressed
+   almost to zero.
+
+   Finally, attachments (non-text email bodies) are transmitted, either
+   in binary form or encoded with base-64.
+
+   When attachments are retrieved in binary form, DEFLATE may be able to
+   compress them, but the format of the attachment is usually not IMAP-
+   like, so the dictionary built while compressing IMAP does not help.
+   The compressor has to adapt its dictionary from IMAP to the
+   attachment's format, and then back.  A few file formats aren't
+   compressible at all using deflate, e.g., .gz, .zip, and .jpg files.
+
+   When attachments are retrieved in base-64 form, the same problems
+   apply, but the base-64 encoding adds another problem.  8-bit
+   compression algorithms such as deflate work well on 8-bit file
+   formats, however base-64 turns a file into something resembling 6-bit
+   bytes, hiding most of the 8-bit file format from the compressor.
+
+   When using the zlib library (see [RFC1951]), the functions
+   deflateInit2(), deflate(), inflateInit2(), and inflate() suffice to
+   implement this extension.  The windowBits value must be in the range
+   -8 to -15, or else deflateInit2() uses the wrong format.
+   deflateParams() can be used to improve compression rate and resource
+   use.  The Z_FULL_FLUSH argument to deflate() can be used to clear the
+   dictionary (the receiving peer does not need to do anything).
+
+   A client can improve downstream compression by implementing BINARY
+   (defined in [RFC3516]) and using FETCH BINARY instead of FETCH BODY.
+   In the author's experience, the improvement ranges from 5% to 40%
+   depending on the attachment being downloaded.
+
+   A server can improve downstream compression if it hints to the
+   compressor that the data type is about to change strongly, e.g., by
+   sending a Z_FULL_FLUSH at the start and end of large non-text
+   literals (before and after '*CHAR8' in the definition of literal in
+   RFC 3501, page 86).  Small literals are best left alone.  A possible
+   boundary is 5k.
+
+
+
+Gulbrandsen                 Standards Track                     [Page 5]
+
+RFC 4978              The IMAP COMPRESS Extension            August 2007
+
+
+   A server can improve the CPU efficiency both of the server and the
+   client if it adjusts the compression level (e.g., using the
+   deflateParams() function in zlib) at these points, to avoid trying to
+   compress incompressible attachments.  A very simple strategy is to
+   change the level to 0 at the start of a literal provided the first
+   two bytes are either 0x1F 0x8B (as in deflate-compressed files) or
+   0xFF 0xD8 (JPEG), and to keep it at 1-5 the rest of the time.  More
+   complex strategies are possible.
+
+5.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [RFC4234].  This syntax augments
+   the grammar specified in [RFC3501].  [RFC4234] defines SP and
+   [RFC3501] defines command-auth, capability, and resp-text-code.
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper or lower case characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+       command-auth =/ compress
+
+       compress    = "COMPRESS" SP algorithm
+
+       capability  =/ "COMPRESS=" algorithm
+                     ;; multiple COMPRESS capabilities allowed
+
+       algorithm   = "DEFLATE"
+
+       resp-text-code =/ "COMPRESSIONACTIVE"
+
+   Note that due the syntax of capability names, future algorithm names
+   must be atoms.
+
+6.  Security Considerations
+
+   As for TLS compression [RFC3749].
+
+7.  IANA Considerations
+
+   The IANA has added COMPRESS=DEFLATE to the list of IMAP capabilities.
+
+
+
+
+
+
+
+
+
+Gulbrandsen                 Standards Track                     [Page 6]
+
+RFC 4978              The IMAP COMPRESS Extension            August 2007
+
+
+8.  Acknowledgements
+
+   Eric Burger, Dave Cridland, Tony Finch, Ned Freed, Philip Guenther,
+   Randall Gellens, Tony Hansen, Cullen Jennings, Stephane Maes, Alexey
+   Melnikov, Lyndon Nerenberg, and Zoltan Ordogh have all helped with
+   this document.
+
+   The author would also like to thank various people in the rooms at
+   meetings, whose help is real, but not reflected in the author's
+   mailbox.
+
+9.  References
+
+9.1.  Normative References
+
+   [RFC1951]  Deutsch, P., "DEFLATE Compressed Data Format Specification
+              version 1.3", RFC 1951, May 1996.
+
+   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC3501]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+              4rev1", RFC 3501, March 2003.
+
+   [RFC4234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
+              Specifications: ABNF", RFC 4234, October 2005.
+
+9.2.  Informative References
+
+   [RFC1962]  Rand, D., "The PPP Compression Control Protocol (CCP)",
+              RFC 1962, June 1996.
+
+   [RFC3516]  Nerenberg, L., "IMAP4 Binary Content Extension", RFC 3516,
+              April 2003.
+
+   [RFC3749]  Hollenbeck, S., "Transport Layer Security Protocol
+              Compression Methods", RFC 3749, May 2004.
+
+   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
+              (TLS) Protocol Version 1.1", RFC 4346, April 2006.
+
+   [RFC4422]  Melnikov, A. and  K. Zeilenga, "Simple Authentication and
+              Security Layer (SASL)", RFC 4422, June 2006.
+
+   [V42BIS]   ITU, "V.42bis: Data compression procedures for data
+              circuit-terminating equipment (DCE) using error correction
+              procedures", http://www.itu.int/rec/T-REC-V.42bis, January
+              1990.
+
+
+
+Gulbrandsen                 Standards Track                     [Page 7]
+
+RFC 4978              The IMAP COMPRESS Extension            August 2007
+
+
+   [MNP]      Gilbert Held, "The Complete Modem Reference", Second
+              Edition, Wiley Professional Computing, ISBN 0-471-00852-4,
+              May 1994.
+
+Author's Address
+
+    Arnt Gulbrandsen
+    Oryx Mail Systems GmbH
+    Schweppermannstr. 8
+    D-81671 Muenchen
+    Germany
+
+    Fax: +49 89 4502 9758
+    EMail: arnt@oryx.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen                 Standards Track                     [Page 8]
+
+RFC 4978              The IMAP COMPRESS Extension            August 2007
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2007).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen                 Standards Track                     [Page 9]
+
diff --git a/imap/docs/rfc/rfc5032.txt b/imap/docs/rfc/rfc5032.txt
new file mode 100644
index 00000000..f8e48953
--- /dev/null
+++ b/imap/docs/rfc/rfc5032.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group                                     E. Burger, Ed.
+Request for Comments: 5032                             BEA Systems, Inc.
+Updates: 3501                                             September 2007
+Category: Standards Track
+
+
+              WITHIN Search Extension to the IMAP Protocol
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   This document describes the WITHIN extension to IMAP SEARCH.  IMAP
+   SEARCH returns messages whose internal date is within or outside a
+   specified interval.  The mechanism described here, OLDER and YOUNGER,
+   differs from BEFORE and SINCE in that the client specifies an
+   interval, rather than a date.  WITHIN is useful for persistent
+   searches where either the device does not have the capacity to
+   perform the search at regular intervals or the network is of limited
+   bandwidth and thus there is a desire to reduce network traffic from
+   sending repeated requests and redundant responses.
+
+1.  Introduction
+
+   This extension exposes two new search keys, OLDER and YOUNGER, each
+   of which takes a non-zero integer argument corresponding to a time
+   interval in seconds.  The server calculates the time of interest by
+   subtracting the time interval the client presents from the current
+   date and time of the server.  The server then either returns messages
+   older or younger than the resultant time and date, depending on the
+   search key used.
+
+1.1.  Conventions Used in This Document
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server, respectively.
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in RFC 2119 [RFC2119].
+
+
+
+
+
+Burger                      Standards Track                     [Page 1]
+
+RFC 5032                     Search Within                September 2007
+
+
+   When describing the general syntax, we omit some definitions, as RFC
+   3501 [RFC3501] defines them.
+
+2.  Protocol Operation
+
+   An IMAP4 server that supports the capability described here MUST
+   return "WITHIN" as one of the server supported capabilities in the
+   CAPABILITY command.
+
+   For both the OLDER and YOUNGER search keys, the server calculates a
+   target date and time by subtracting the interval, specified in
+   seconds, from the current date and time of the server.  The server
+   then compares the target time with the INTERNALDATE of the message,
+   as specified in IMAP [RFC3501].  For OLDER, messages match if the
+   INTERNALDATE is less recent than or equal to the target time.  For
+   YOUNGER, messages match if the INTERNALDATE is more recent than or
+   equal to the target time.
+
+   Both OLDER and YOUNGER searches always result in exact matching, to
+   the resolution of a second.  However, if one is doing a dynamic
+   evaluation, for example, in a context [CONTEXT], one needs to be
+   aware that the server might perform the evaluation periodically.
+   Thus, the server may delay the updates.  Clients MUST be aware that
+   dynamic search results may not reflect the current state of the
+   mailbox.  If the client needs a search result that reflects the
+   current state of the mailbox, we RECOMMEND that the client issue a
+   new search.
+
+3.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation.  Elements not defined here can be found in the
+   formal syntax of ABNF [RFC4234] and IMAP [RFC3501].
+
+   This document extends RFC 3501 [RFC3501] with two new search keys:
+   OLDER <interval> and YOUNGER <interval>.
+
+   search-key =/ ( "OLDER" / "YOUNGER" ) SP nz-number
+                  ; search-key defined in RFC 3501
+
+4.  Example
+
+   C: a1 SEARCH UNSEEN YOUNGER 259200
+   S: a1 * SEARCH 4 8 15 16 23 42
+
+   Search for all unseen messages within the past 3 days, or 259200
+   seconds, according to the server's current time.
+
+
+
+
+Burger                      Standards Track                     [Page 2]
+
+RFC 5032                     Search Within                September 2007
+
+
+5.  Security Considerations
+
+   The WITHIN extension does not raise any security considerations that
+   are not present in the base protocol.  Considerations are the same as
+   for IMAP [RFC3501].
+
+6.  IANA Considerations
+
+   Per the IMAP RFC [RFC3501], registration of a new IMAP capability in
+   the IMAP Capability registry requires the publication of a standards-
+   track RFC or an IESG approved experimental RFC.  The registry is
+   currently located at
+   <http://www.iana.org/assignments/imap4-capabilities>.  This
+   standards-track document defines the WITHIN IMAP capability.  IANA
+   has added this extension to the IANA IMAP Capability registry.
+
+7.  References
+
+7.1.  Normative References
+
+   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", RFC 2119, BCP 14, March 1997.
+
+   [RFC3501]  Crispin, M., "Internet Message Access Protocol - Version
+              4rev1", RFC 3501, March 2003.
+
+   [RFC4234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
+              Specifications: ABNF", RFC 4234, October 2005.
+
+7.2.  Informative References
+
+   [CONTEXT]  Melnikov, D. and C. King, "Contexts for IMAP4", Work
+              in Progress, May 2006.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Burger                      Standards Track                     [Page 3]
+
+RFC 5032                     Search Within                September 2007
+
+
+Appendix A.  Contributors
+
+   Stephane Maes and Ray Cromwell wrote the original version of this
+   document as part of P-IMAP, as well as the first versions for the
+   IETF.  From an attribution perspective, they are clearly authors.
+
+Appendix B.  Acknowledgements
+
+   The authors want to thank all who have contributed key insight and
+   who have extensively reviewed and discussed the concepts of LPSEARCH.
+   They also thank the authors of its early introduction in P-IMAP.
+
+   We also want to give a special thanks to Arnt Gilbrandsen, Ken
+   Murchison, Zoltan Ordogh, and most especially Dave Cridland for their
+   review and suggestions.  A special thank you goes to Alexey Melnikov
+   for his choice submission of text.
+
+Author's Address
+
+   Eric W. Burger (editor)
+   BEA Systems, Inc.
+   USA
+
+   EMail: eric.burger@bea.com
+   URI:   http://www.standardstrack.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Burger                      Standards Track                     [Page 4]
+
+RFC 5032                     Search Within                September 2007
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2007).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Burger                      Standards Track                     [Page 5]
+
diff --git a/imap/docs/rfc/rfc5051.txt b/imap/docs/rfc/rfc5051.txt
new file mode 100644
index 00000000..0a4479ca
--- /dev/null
+++ b/imap/docs/rfc/rfc5051.txt
@@ -0,0 +1,395 @@
+
+
+
+
+
+
+Network Working Group                                         M. Crispin
+Request for Comments: 5051                      University of Washington
+Category: Standards Track                                   October 2007
+
+
+         i;unicode-casemap - Simple Unicode Collation Algorithm
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   This document describes "i;unicode-casemap", a simple case-
+   insensitive collation for Unicode strings.  It provides equality,
+   substring, and ordering operations.
+
+1.  Introduction
+
+   The "i;ascii-casemap" collation described in [COMPARATOR] is quite
+   simple to implement and provides case-independent comparisons for the
+   26 Latin alphabetics.  It is specified as the default and/or baseline
+   comparator in some application protocols, e.g., [IMAP-SORT].
+
+   However, the "i;ascii-casemap" collation does not produce
+   satisfactory results with non-ASCII characters.  It is possible, with
+   a modest extension, to provide a more sophisticated collation with
+   greater multilingual applicability than "i;ascii-casemap".  This
+   extension provides case-independent comparisons for a much greater
+   number of characters.  It also collates characters with diacriticals
+   with the non-diacritical character forms.
+
+   This collation, "i;unicode-casemap", is intended to be an alternative
+   to, and preferred over, "i;ascii-casemap".  It does not replace the
+   "i;basic" collation described in [BASIC].
+
+2.  Unicode Casemap Collation Description
+
+   The "i;unicode-casemap" collation is a simple collation which is
+   case-insensitive in its treatment of characters.  It provides
+   equality, substring, and ordering operations.  The validity test
+   operation returns "valid" for any input.
+
+
+
+
+
+Crispin                     Standards Track                     [Page 1]
+
+RFC 5051                   i;unicode-casemap                October 2007
+
+
+   This collation allows strings in arbitrary (and mixed) character
+   sets, as long as the character set for each string is identified and
+   it is possible to convert the string to Unicode.  Strings which have
+   an unidentified character set and/or cannot be converted to Unicode
+   are not rejected, but are treated as binary.
+
+   Each input string is prepared by converting it to a "titlecased
+   canonicalized UTF-8" string according to the following steps, using
+   UnicodeData.txt ([UNICODE-DATA]):
+
+      (1) A Unicode codepoint is obtained from the input string.
+
+          (a) If the input string is in a known charset that can be
+              converted to Unicode, a sequence in the string's charset
+              is read and checked for validity according to the rules of
+              that charset.  If the sequence is valid, it is converted
+              to a Unicode codepoint.  Note that for input strings in
+              UTF-8, the UTF-8 sequence must be valid according to the
+              rules of [UTF-8]; e.g., overlong UTF-8 sequences are
+              invalid.
+
+          (b) If the input string is in an unknown charset, or an
+              invalid sequence occurs in step (1)(a), conversion ceases.
+              No further preparation is performed, and any partial
+              preparation results are discarded.  The original string is
+              used unchanged with the i;octet comparator.
+
+      (2) The following steps, using UnicodeData.txt ([UNICODE-DATA]),
+          are performed on the resulting codepoint from step (1)(a).
+
+          (a) If the codepoint has a titlecase property in
+              UnicodeData.txt (this is normally the same as the
+              uppercase property), the codepoint is converted to the
+              codepoints in the titlecase property.
+
+          (b) If the resulting codepoint from (2)(a) has a decomposition
+              property of any type in UnicodeData.txt, the codepoint is
+              converted to the codepoints in the decomposition property.
+              This step is recursively applied to each of the resulting
+              codepoints until no more decomposition is possible
+              (effectively Normalization Form KD).
+
+          Example: codepoint U+01C4 (LATIN CAPITAL LETTER DZ WITH CARON)
+          has a titlecase property of U+01C5 (LATIN CAPITAL LETTER D
+          WITH SMALL LETTER Z WITH CARON).  Codepoint U+01C5 has a
+          decomposition property of U+0044 (LATIN CAPITAL LETTER D)
+          U+017E (LATIN SMALL LETTER Z WITH CARON).  U+017E has a
+          decomposition property of U+007A (LATIN SMALL LETTER Z) U+030c
+
+
+
+Crispin                     Standards Track                     [Page 2]
+
+RFC 5051                   i;unicode-casemap                October 2007
+
+
+          (COMBINING CARON).  Neither U+0044, U+007A, nor U+030C have
+          any decomposition properties.  Therefore, U+01C4 is converted
+          to U+0044 U+007A U+030C by this step.
+
+      (3) The resulting codepoint(s) from step (2) is/are appended, in
+          UTF-8 format, to the "titlecased canonicalized UTF-8" string.
+
+      (4) Repeat from step (1) until there is no more data in the input
+          string.
+
+   Following the above preparation process on each string, the equality,
+   ordering, and substring operations are as for i;octet.
+
+   It is permitted to use an alternative implementation of the above
+   preparation process if it produces the same results.  For example, it
+   may be more convenient for an implementation to convert all input
+   strings to a sequence of UTF-16 or UTF-32 values prior to performing
+   any of the step (2) actions.  Similarly, if all input strings are (or
+   are convertible to) Unicode, it may be possible to use UTF-32 as an
+   alternative to UTF-8 in step (3).
+
+      Note: UTF-16 is unsuitable as an alternative to UTF-8 in step (3),
+      because UTF-16 surrogates will cause i;octet to collate codepoints
+      U+E0000 through U+FFFF after non-BMP codepoints.
+
+   This collation is not locale sensitive.  Consequently, care should be
+   taken when using OS-supplied functions to implement this collation.
+   Functions such as strcasecmp and toupper are sometimes locale
+   sensitive and may inconsistently casemap letters.
+
+   The i;unicode-casemap collation is well suited to use with many
+   Internet protocols and computer languages.  Use with natural language
+   is often inappropriate; even though the collation apparently supports
+   languages such as Swahili and English, in real-world use it tends to
+   mis-sort a number of types of string:
+
+   o  people and place names containing scripts that are not collated
+      according to "alphabetical order".
+   o  words with characters that have diacriticals.  However,
+      i;unicode-casemap generally does a better job than i;ascii-casemap
+      for most (but not all) languages.  For example, German umlaut
+      letters will sort correctly, but some Scandinavian letters will
+      not.
+   o  names such as "Lloyd" (which in Welsh sorts after "Lyon", unlike
+      in English),
+   o  strings containing other non-letter symbols; e.g., euro and pound
+      sterling symbols, quotation marks other than '"', dashes/hyphens,
+      etc.
+
+
+
+Crispin                     Standards Track                     [Page 3]
+
+RFC 5051                   i;unicode-casemap                October 2007
+
+
+3.  Unicode Casemap Collation Registration
+
+   <?xml version='1.0'?>
+   <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+   <collation rfc="5051" scope="global" intendedUse="common">
+   <identifier>i;unicode-casemap</identifier>
+   <title>Unicode Casemap</title>
+   <operations>equality order substring</operations>
+   <specification>RFC 5051</specification>
+   <owner>IETF</owner>
+   <submitter>mrc@cac.washington.edu</submitter>
+   </collation>
+
+4.  Security Considerations
+
+   The security considerations for [UTF-8], [STRINGPREP], and [UNICODE-
+   SECURITY] apply and are normative to this specification.
+
+   The results from this comparator will vary depending upon the
+   implementation for several reasons.  Implementations MUST consider
+   whether these possibilities are a problem for their use case:
+
+   1) New characters added in Unicode may have decomposition or
+      titlecase properties that will not be known to an implementation
+      based upon an older revision of Unicode.  This impacts step (2).
+
+   2) Step (2)(b) defines a subset of Normalization Form KD (NFKD) that
+      does not require normalization of out-of-order diacriticals.
+      However, an implementation MAY use an NFKD library routine that
+      does such normalization.  This impacts step (2)(b) and possibly
+      also step (1)(a), and is an issue only with ill-formed UTF-8
+      input.
+
+   3) The set of charsets handled in step (1)(a) is open-ended.  UTF-8
+      (and, by extension, US-ASCII) are the only mandatory-to-implement
+      charsets.  This impacts step (1)(a).
+
+      Implementations SHOULD, as far as feasible, support all the
+      charsets they are likely to encounter in the input data, in order
+      to avoid poor collation caused by the fall through to the (1)(b)
+      rule.
+
+   4) Other charsets may have revisions which add new characters that
+      are not known to an implementation based upon an older revision.
+      This impacts step (1)(a) and possibly also step (1)(b).
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 4]
+
+RFC 5051                   i;unicode-casemap                October 2007
+
+
+   An attacker may create input that is ill-formed or in an unknown
+   charset, with the intention of impacting the results of this
+   comparator or exploiting other parts of the system which process this
+   input in different ways.  Note, however, that even well-formed data
+   in a known charset can impact the result of this comparator in
+   unexpected ways.  For example, an attacker can substitute U+0041
+   (LATIN CAPITAL LETTER A) with U+0391 (GREEK CAPITAL LETTER ALPHA) or
+   U+0410 (CYRILLIC CAPITAL LETTER A) in the intention of causing a
+   non-match of strings which visually appear the same and/or causing
+   the string to appear elsewhere in a sort.
+
+5.  IANA Considerations
+
+   The i;unicode-casemap collation defined in section 2 has been added
+   to the registry of collations defined in [COMPARATOR].
+
+6.  Normative References
+
+   [COMPARATOR]          Newman, C., Duerst, M., and A. Gulbrandsen,
+                         "Internet Application Protocol Collation
+                         Registry", RFC 4790, February 2007.
+
+   [STRINGPREP]          Hoffman, P. and M. Blanchet, "Preparation of
+                         Internationalized Strings ("stringprep")", RFC
+                         3454, December 2002.
+
+   [UTF-8]               Yergeau, F., "UTF-8, a transformation format of
+                         ISO 10646", STD 63, RFC 3629, November 2003.
+
+   [UNICODE-DATA]        <http://www.unicode.org/Public/UNIDATA/
+                         UnicodeData.txt>
+
+                         Although the UnicodeData.txt file referenced
+                         here is part of the Unicode standard, it is
+                         subject to change as new characters are added
+                         to Unicode and errors are corrected in Unicode
+                         revisions.  As a result, it may be less stable
+                         than might otherwise be implied by the
+                         standards status of this specification.
+
+   [UNICODE-SECURITY]    Davis, M. and M. Suignard, "Unicode Security
+                         Considerations", February 2006,
+                         <http://www.unicode.org/reports/tr36/>.
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 5]
+
+RFC 5051                   i;unicode-casemap                October 2007
+
+
+7.  Informative References
+
+   [BASIC]               Newman, C., Duerst, M., and A. Gulbrandsen,
+                         "i;basic - the Unicode Collation Algorithm",
+                         Work in Progress, March 2007.
+
+   [IMAP-SORT]           Crispin, M. and K. Murchison, "Internet Message
+                         Access Protocol - SORT and THREAD Extensions",
+                         Work in Progress, September 2007.
+
+Author's Address
+
+   Mark R. Crispin
+   Networks and Distributed Computing
+   University of Washington
+   4545 15th Avenue NE
+   Seattle, WA  98105-4527
+
+   Phone: +1 (206) 543-5762
+   EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 6]
+
+RFC 5051                   i;unicode-casemap                October 2007
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2007).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin                     Standards Track                     [Page 7]
+
diff --git a/imap/docs/rfc/rfc5092.txt b/imap/docs/rfc/rfc5092.txt
new file mode 100644
index 00000000..ab87f350
--- /dev/null
+++ b/imap/docs/rfc/rfc5092.txt
@@ -0,0 +1,1795 @@
+
+
+
+
+
+
+Network Working Group                                   A. Melnikov, Ed.
+Request for Comments: 5092                                    Isode Ltd.
+Obsoletes: 2192                                                C. Newman
+Updates: 4467                                           Sun Microsystems
+Category: Standards Track                                  November 2007
+
+
+                            IMAP URL Scheme
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   IMAP (RFC 3501) is a rich protocol for accessing remote message
+   stores.  It provides an ideal mechanism for accessing public mailing
+   list archives as well as private and shared message stores.  This
+   document defines a URL scheme for referencing objects on an IMAP
+   server.
+
+   This document obsoletes RFC 2192.  It also updates RFC 4467.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
+
+
+
+
+
+Melnikov & Newman           Standards Track                     [Page 1]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+Table of Contents
+
+   1. Introduction ....................................................2
+   2. Conventions Used in This Document ...............................3
+   3. IMAP userinfo Component (iuserinfo) .............................4
+      3.1. IMAP Mailbox Naming Scope ..................................4
+      3.2. IMAP User Name and Authentication Mechanism ................4
+      3.3. Limitations of enc-user ....................................6
+   4. IMAP Server .....................................................7
+   5. Lists of Messages ...............................................7
+   6. A Specific Message or Message Part ..............................8
+      6.1. URLAUTH Authorized URL .....................................9
+           6.1.1. Concepts ............................................9
+                  6.1.1.1. URLAUTH ....................................9
+                  6.1.1.2. Mailbox Access Key .........................9
+                  6.1.1.3. Authorized Access Identifier ...............9
+                  6.1.1.4. Authorization Mechanism ...................10
+                  6.1.1.5. Authorization Token .......................10
+           6.1.2. URLAUTH Extensions to IMAP URL .....................10
+   7. Relative IMAP URLs .............................................11
+      7.1. absolute-path References ..................................12
+      7.2. relative-path References ..................................12
+   8. Internationalization Considerations ............................13
+   9. Examples .......................................................13
+      9.1. Examples of Relative URLs .................................16
+   10. Security Considerations .......................................16
+      10.1. Security Considerations Specific to URLAUTH Authorized
+            URL ......................................................17
+   11. ABNF for IMAP URL Scheme ......................................17
+   12. IANA Considerations ...........................................21
+      12.1. IANA Registration of imap: URI Scheme ....................21
+   13. References ....................................................22
+      13.1. Normative References .....................................22
+      13.2. Informative References ...................................23
+   Appendix A. Sample Code............................................24
+   Appendix B. List of Changes since RFC 2192.........................30
+   Appendix C. List of Changes since RFC 4467.........................31
+   Appendix D. Acknowledgments........................................31
+
+1.  Introduction
+
+   The IMAP URL scheme is used to designate IMAP servers, mailboxes,
+   messages, MIME bodies [MIME], and search programs on Internet hosts
+   accessible using the IMAP protocol over TCP.
+
+   The IMAP URL follows the common Internet scheme syntax as defined in
+   [URI-GEN].  If :<port> is omitted, the port defaults to 143 (as
+   defined in Section 2.1 of [IMAP4]).
+
+
+
+Melnikov & Newman           Standards Track                     [Page 2]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   An absolute IMAP URL takes one of the following forms:
+
+      imap://<iserver>[/]
+
+      imap://<iserver>/<enc-mailbox>[<uidvalidity>][?<enc-search>]
+
+      imap://<iserver>/<enc-mailbox>[<uidvalidity>]<iuid>
+       [<isection>][<ipartial>][<iurlauth>]
+
+   The first form is used to refer to an IMAP server (see Section 4),
+   the second form refers to the contents of a mailbox or a set of
+   messages resulting from a search (see Section 5), and the final form
+   refers to a specific message or message part, and possibly a byte
+   range in that part (see Section 6).  If [URLAUTH] extension is
+   supported, then the final form can have the <iurlauth> component (see
+   Section 6.1 for more details).
+
+   The <iserver> component common to all types of absolute IMAP URLs has
+   the following syntax expressed in ABNF [ABNF]:
+
+      [iuserinfo "@"] host [ ":" port ]
+
+   The <iserver> component is the same as "authority" defined in
+   [URI-GEN].  The syntax and uses of the <iuserinfo> ("IMAP userinfo
+   component") are described in detail in Section 3.  The syntax of
+   <host> and <port> is described in [URI-GEN].
+
+2.  Conventions Used in This Document
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+   This document references many productions from [URI-GEN].  When the
+   document needs to emphasize IMAP URI-specific differences from [URI-
+   GEN] (i.e., for parts of IMAP URIs that have more restricted syntax
+   than generic URIs), it uses a non-terminal i<foo> to define an IMAP-
+   specific version of the non-terminal <foo> from [URI-GEN].
+
+   Note that the ABNF syntax shown in Section 11 is normative.  Sections
+   2-6 may use a less formal syntax that does not necessarily match the
+   normative ABNF shown in Section 11.  If there are any differences
+   between the syntax shown in Sections 2-6 and Section 11, then the
+   syntax shown in Section 11 must be treated as authoritative.  Non-
+   syntax requirements included in Sections 2-6 are, of course,
+   normative.
+
+
+
+
+
+Melnikov & Newman           Standards Track                     [Page 3]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+3.  IMAP userinfo Component (iuserinfo)
+
+   The <iuserinfo> component conforms to the generic syntax of
+   <userinfo> defined in [URI-GEN].  It has the following syntax
+   expressed in ABNF [ABNF]:
+
+      enc-user [iauth] / [enc-user] iauth
+
+   The meaning of the different parts is described in subsections of
+   this section.
+
+3.1.  IMAP Mailbox Naming Scope
+
+   The "enc-user" part of the "iuserinfo" component, if present, denotes
+   mailbox naming scope.  If it is absent, the IMAP URL can only
+   reference mailboxes with globally unique names, i.e., mailboxes with
+   names that don't change depending on the user the client
+   authenticated as to the IMAP server.  Note that not all IMAP
+   implementations support globally unique names.
+
+   For example, a personal mailbox described by the following URL
+   <imap://michael@example.org/INBOX> is most likely different from a
+   personal mailbox described by <imap://bester@example.org/INBOX>, even
+   though both URLs use the same mailbox name.
+
+3.2.  IMAP User Name and Authentication Mechanism
+
+   The userinfo component (see [URI-GEN]) of an IMAP URI may contain an
+   IMAP user name (a.k.a. authorization identity [SASL], "enc-user")
+   and/or an authentication mechanism. (Note that the "enc-user" also
+   defines a mailbox naming scope as described in Section 3.1).  The
+   IMAP user name and the authentication mechanism are used in the
+   "LOGIN" or "AUTHENTICATE" commands after making the connection to the
+   IMAP server.
+
+   If no user name and no authentication mechanism are supplied, the
+   client MUST authenticate as anonymous to the server.  If the server
+   advertises AUTH=ANONYMOUS IMAP capability, the client MUST use the
+   AUTHENTICATE command with ANONYMOUS [ANONYMOUS] SASL mechanism.  If
+   SASL ANONYMOUS is not available, the (case-insensitive) user name
+   "anonymous" is used with the "LOGIN" command and the Internet email
+   address of the end user accessing the resource is supplied as the
+   password.  The latter option is given in order to provide for
+   interoperability with deployed servers.
+
+   Note that, as described in RFC 3501, the "LOGIN" command MUST NOT be
+   used when the IMAP server advertises the LOGINDISABLED capability.
+
+
+
+
+Melnikov & Newman           Standards Track                     [Page 4]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   An authentication mechanism (as used by the IMAP AUTHENTICATE
+   command) can be expressed by adding ";AUTH=<enc-auth-type>" to the
+   end of the user name in an IMAP URL.  When such an <enc-auth-type> is
+   indicated, the client SHOULD request appropriate credentials from
+   that mechanism and use the "AUTHENTICATE" command instead of the
+   "LOGIN" command.  If no user name is specified, one MUST be obtained
+   from the mechanism or requested from the user/configuration as
+   appropriate.
+
+   The string ";AUTH=*" indicates that the client SHOULD select an
+   appropriate authentication mechanism.  (Though the '*' character in
+   this usage is not strictly a delimiter, it is being treated like a
+   sub-delim [URI-GEN] in this instance.  It MUST NOT be percent-encoded
+   in this usage, as ";AUTH=%2A" will not match this production.)  It
+   MAY use any mechanism listed in the response to the CAPABILITY
+   command (or CAPABILITY response code) or use an out-of-band security
+   service resulting in a PREAUTH connection.  If no user name is
+   specified and no appropriate authentication mechanisms are available,
+   the client SHOULD fall back to anonymous login as described above.
+   The behavior prescribed in this section allows a URL that grants
+   read-write access to authorized users and read-only anonymous access
+   to other users.
+
+   If a user name is included with no authentication mechanism, then
+   ";AUTH=*" is assumed.
+
+   Clients must take care when resolving a URL that requires or requests
+   any sort of authentication, since URLs can easily come from untrusted
+   sources.  Supplying authentication credentials to the wrong server
+   may compromise the security of the user's account; therefore, the
+   program resolving the URL should meet at least one of the following
+   criteria in this case:
+
+   1) The URL comes from a trusted source, such as a referral server
+      that the client has validated and trusts according to site policy.
+      Note that user entry of the URL may or may not count as a trusted
+      source, depending on the experience level of the user and site
+      policy.
+
+   2) Explicit local site policy permits the client to connect to the
+      server in the URL.  For example, a company example.com may have a
+      site policy to trust all IMAP server names ending in example.com,
+      whereas such a policy would be unwise for example.edu where random
+      students can set up IMAP servers.
+
+   3) The user confirms that connecting to that domain name with the
+      specified credentials and/or mechanism is permitted.  For example,
+      when using "LOGIN" or SASL PLAIN with Transport Layer Security
+
+
+
+Melnikov & Newman           Standards Track                     [Page 5]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+      (TLS), the IMAP URL client presents a dialog box "Is it OK to send
+      your password to server "example.com"?  Please be aware the owners
+      of example.com will be able to reuse your password to connect to
+      other servers on your behalf".
+
+   4) A mechanism is used that validates the server before passing
+      potentially compromising client credentials.  For example, a site
+      has a designated TLS certificate used to certify site-trusted IMAP
+      server certificates, and this has been configured explicitly into
+      the IMAP URL client.  Another example is use of a Simple
+      Authentication and Security Layer (SASL) mechanism such as
+      DIGEST-MD5 [DIGEST-MD5], which supports mutual authentication.
+
+   5) An authentication mechanism is used that will not reveal any
+      information to the server that could be used to compromise future
+      connections.  Examples are SASL ANONYMOUS [ANONYMOUS] or GSSAPI
+      [GSSAPI].
+
+   URLs that do not include a user name but include an authentication
+   mechanism (";AUTH=<mech>") must be treated with extra care, since for
+   some <mech>s they are more likely to compromise the user's primary
+   account.  A URL containing ";AUTH=*" must also be treated with extra
+   care since it might fall back on a weaker security mechanism.
+   Finally, clients are discouraged from using a plaintext password as a
+   fallback with ";AUTH=*" unless the connection has strong encryption.
+
+   A program interpreting IMAP URLs MAY cache open connections to an
+   IMAP server for later reuse.  If a URL contains a user name, only
+   connections authenticated as that user may be reused.  If a URL does
+   not contain a user name or authentication mechanism, then only an
+   anonymous connection may be reused.
+
+   Note that if unsafe or reserved characters such as " " (space) or ";"
+   are present in the user name or authentication mechanism, they MUST
+   be percent-encoded as described in [URI-GEN].
+
+3.3.  Limitations of enc-user
+
+   As per Sections 3.1 and 3.2 of this document, the IMAP URI enc-user
+   has two purposes:
+
+      1) It provides context for user-specific mailbox paths such as
+         "INBOX" (Section 3.1).
+
+      2) It specifies that resolution of the URL requires logging in as
+         that user and limits use of that URL to only that user (Section
+         3.2).
+
+
+
+
+Melnikov & Newman           Standards Track                     [Page 6]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   An obvious limitation of using the same field for both purposes is
+   that the URL can be resolved only by the mailbox owner.  In order to
+   avoid this restriction, implementations should use globally unique
+   mailbox names (see Section 3.1) whenever possible.
+
+      Note: There is currently no general way in IMAP of learning a
+      globally unique name for a mailbox.  However, by looking at the
+      NAMESPACE [NAMESPACE] command result, it is possible to determine
+      whether or not a mailbox name is globally unique.
+
+   The URLAUTH component overrides the second purpose of the enc-user in
+   the IMAP URI and by default permits the URI to be resolved by any
+   user permitted by the <access> identifier.  URLAUTH and <access>
+   identifier are described in Section 6.1.
+
+4.  IMAP Server
+
+   An IMAP URL referring to an IMAP server has the following form:
+
+      imap://<iserver>[/]
+
+   This URL type is frequently used to describe a location of an IMAP
+   server, both in referrals and in configuration.  It may optionally
+   contain the <iuserinfo> component (see Sections 3 and 11).  A program
+   interpreting this URL would issue the standard set of commands it
+   uses to present a view of the content of the IMAP server, as visible
+   to the user described by the "enc-user" part of the <iuserinfo>
+   component, if the "enc-user" part is specified.
+
+5.  Lists of Messages
+
+   An IMAP URL referring to a list of messages has the following form:
+
+      imap://<iserver>/<enc-mailbox>[<uidvalidity>][?<enc-search>]
+
+   The <enc-mailbox> field is used as the argument to the IMAP4 "SELECT"
+   or "EXAMINE" command.  Note that if unsafe or reserved characters
+   such as " " (space), ";", or "?" are present in <enc-mailbox>, they
+   MUST be percent-encoded as described in [URI-GEN].
+
+   The <uidvalidity> field is optional.  If it is present, it MUST be
+   the same as the value of IMAP4 UIDVALIDITY response code at the time
+   the URL was created.  This MUST be used by the program interpreting
+   the IMAP URL to determine if the URL is stale.  If the IMAP URL is
+   stale, then the program should behave as if the corresponding mailbox
+   doesn't exist.
+
+
+
+
+
+Melnikov & Newman           Standards Track                     [Page 7]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   Note that the <uidvalidity> field is a modifier to the <enc-mailbox>,
+   i.e., it is considered a part of the last "component" (as used in
+   [URI-GEN]) of the <enc-mailbox>.  This is significant during relative
+   URI resolution.
+
+   The "?<enc-search>" field is optional.  If it is not present, the
+   program interpreting the URL will present the entire content of the
+   mailbox.
+
+   If the "?<enc-search>" field is present, the program interpreting the
+   URL should use the contents of this field as arguments following an
+   IMAP4 SEARCH command.  These arguments are likely to contain unsafe
+   characters such as " " (space) (which are likely to be present in the
+   <enc-search>).  If unsafe characters are present, they MUST be
+   percent-encoded as described in [URI-GEN].
+
+   Note that quoted strings and non-synchronizing literals [LITERAL+]
+   are allowed in the <enc-search> content; however, synchronizing
+   literals are not allowed, as their presence would effectively mean
+   that the agent interpreting IMAP URLs needs to parse an <enc-search>
+   content, find all synchronizing literals, and perform proper command
+   continuation request handling (see Sections 4.3 and 7 of [IMAP4]).
+
+6.  A Specific Message or Message Part
+
+   An IMAP URL referring to a specific message or message part has the
+   following form:
+
+      imap://<iserver>/<enc-mailbox>[<uidvalidity>]<iuid>
+      [<isection>][<ipartial>][<iurlauth>]
+
+   The <enc-mailbox> and [uidvalidity] are as defined in Section 5
+   above.
+
+   If <uidvalidity> is present in this form, it SHOULD be used by the
+   program interpreting the URL to determine if the URL is stale.
+
+   The <iuid> refers to an IMAP4 message Unique Identifier (UID), and it
+   SHOULD be used as the <set> argument to the IMAP4 "UID FETCH"
+   command.
+
+   The <isection> field is optional.  If not present, the URL refers to
+   the entire Internet message as returned by the IMAP command "UID
+   FETCH <uid> BODY.PEEK[]".  If present, the URL refers to the object
+   returned by a "UID FETCH <uid> BODY.PEEK[<section>]" command.  The
+   type of the object may be determined by using a "UID FETCH <uid>
+   BODYSTRUCTURE" command and locating the appropriate part in the
+
+
+
+
+Melnikov & Newman           Standards Track                     [Page 8]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   resulting BODYSTRUCTURE.  Note that unsafe characters in [isection]
+   MUST be percent-encoded as described in [URI-GEN].
+
+   The <ipartial> field is optional.  If present, it effectively appends
+   "<<partial-range>>" to the end of the UID FETCH BODY.PEEK[<section>]
+   command constructed as described in the previous paragraph.  In other
+   words, it allows the client to request a byte range of the
+   message/message part.
+
+   The <iurlauth> field is described in detail in Section 6.1.
+
+6.1.  URLAUTH Authorized URL
+
+   URLAUTH authorized URLs are only supported by an IMAP server
+   advertising the URLAUTH IMAP capability [URLAUTH].
+
+6.1.1.  Concepts
+
+6.1.1.1.  URLAUTH
+
+   URLAUTH is a component, appended at the end of a URL, that conveys
+   authorization to access the data addressed by that URL.  It contains
+   an authorized access identifier, an authorization mechanism name, and
+   an authorization token.  The authorization token is generated from
+   the URL, the authorized access identifier, authorization mechanism
+   name, and a mailbox access key.
+
+      Note: This specification only allows for the URLAUTH component in
+      IMAP URLs describing a message or its part.
+
+6.1.1.2.  Mailbox Access Key
+
+   The mailbox access key is an unpredictable, random string.  To ensure
+   unpredictability, the random string with at least 128 bits of entropy
+   is generated by software or hardware (not by the human user).
+
+   Each user has a table of mailboxes and an associated mailbox access
+   key for each mailbox.  Consequently, the mailbox access key is per-
+   user and per-mailbox.  In other words, two users sharing the same
+   mailbox each have a different mailbox access key for that mailbox,
+   and each mailbox accessed by a single user also has a different
+   mailbox access key.
+
+6.1.1.3.  Authorized Access Identifier
+
+   The authorized <access> identifier restricts use of the URLAUTH
+   authorized URL to certain users authorized on the server, as
+   described in Section 6.1.2.
+
+
+
+Melnikov & Newman           Standards Track                     [Page 9]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+6.1.1.4.  Authorization Mechanism
+
+   The authorization mechanism is the algorithm by which the URLAUTH is
+   generated and subsequently verified, using the mailbox access key.
+
+6.1.1.5.  Authorization Token
+
+   The authorization token is a deterministic string of at least 128
+   bits that an entity with knowledge of the secret mailbox access key
+   and URL authorization mechanism can use to verify the URL.
+
+6.1.2.  URLAUTH Extensions to IMAP URL
+
+   A specific message or message part IMAP URL can optionally contain
+   ";EXPIRE=<datetime>" and/or ";URLAUTH=<access>:<mech>:<token>".
+
+   When ";EXPIRE=<datetime>" is used, this indicates the latest date and
+   time that the URL is valid.  After that date and time, the URL has
+   expired and server implementations MUST reject the URL.  If
+   ";EXPIRE=<datetime>" is not used, the URL has no expiration, but can
+   still be revoked using the RESETKEY command [URLAUTH].
+
+   The URLAUTH takes the form ";URLAUTH=<access>:<mech>:<token>", and it
+   MUST be at the end of the URL.  It is composed of three parts.  The
+   <access> portion provides the authorized access identifiers that may
+   constrain the operations and users that are permitted to use this
+   URL.  The <mech> portion provides the authorization mechanism used by
+   the IMAP server to generate the authorization token that follows.
+   The <token> portion provides the authorization token, which can be
+   generated using the GENURLAUTH command [URLAUTH].
+
+   The "submit+" <access> identifier prefix, followed by a userid,
+   indicates that only a userid authorized as a message submission
+   entity on behalf of the specified userid is permitted to use this
+   URL.  The IMAP server does not validate the specified userid but does
+   validate that the IMAP session has an authorization identity that is
+   authorized as a message submission entity.  The authorized message
+   submission entity MUST validate the userid prior to contacting the
+   IMAP server.
+
+   The "user+" <access> identifier prefix, followed by a userid,
+   indicates that use of this URL is limited to IMAP sessions that are
+   logged in as the specified userid (that is, have authorization
+   identity as that userid).
+
+      Note: If a SASL mechanism that provides both authorization and
+      authentication identifiers is used to authenticate to the IMAP
+      server, the "user+" <access> identifier MUST match the
+
+
+
+Melnikov & Newman           Standards Track                    [Page 10]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+      authorization identifier.  If the SASL mechanism can't transport
+      the authorization identifier, the "user+" <access> identifier MUST
+      match the authorization identifier derived from the authentication
+      identifier (see [SASL]).
+
+   The "authuser" <access> identifier indicates that use of this URL is
+   limited to authenticated IMAP sessions that are logged in as any
+   non-anonymous user (that is, have authorization identity as a non-
+   anonymous user) of that IMAP server.  To restate this: use of this
+   type of URL is prohibited to anonymous IMAP sessions, i.e., any
+   URLFETCH command containing this type of URL issued in an anonymous
+   session MUST return NIL in the URLFETCH response.
+
+   The "anonymous" <access> identifier indicates that use of this URL is
+   not restricted by session authorization identity; that is, any IMAP
+   session in authenticated or selected state (as defined in [IMAP4]),
+   including anonymous sessions, may issue a URLFETCH [URLAUTH] using
+   this URL.
+
+   The authorization token is represented as an ASCII-encoded
+   hexadecimal string, which is used to authorize the URL.  The length
+   and the calculation of the authorization token depend upon the
+   mechanism used, but in all cases, the authorization token is at least
+   128 bits (and therefore at least 32 hexadecimal digits).
+
+   Example:
+
+      <imap://joe@example.com/INBOX/;uid=20/;section=1.2;urlauth=
+      submit+fred:internal:91354a473744909de610943775f92038>
+
+7.  Relative IMAP URLs
+
+   Relative IMAP URLs are permitted and are resolved according to the
+   rules defined in [URI-GEN].  In particular, in IMAP URLs parameters
+   (such as ";uid=" or ";section=") are treated as part of the normal
+   path with respect to relative URL resolution.
+
+   [URI-GEN] defines four forms of relative URLs: <inetwork-path>,
+   <iabsolute-path>, <irelative-path>, and <ipath-empty>.  Their syntax
+   is defined in Section 11.
+
+   A relative reference that begins with two slash characters is termed
+   a network-path reference (<inetwork-path>); such references are
+   rarely used, because in most cases they can be replaced with an
+   equivalent absolute URL.  A relative reference that begins with a
+   single slash character is termed an absolute-path reference
+   (<iabsolute-path>; see also Section 7.1).  A relative reference that
+   does not begin with a slash character is termed a relative-path
+
+
+
+Melnikov & Newman           Standards Track                    [Page 11]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   reference (<irelative-path>; see also Section 7.2).  The final form
+   is <ipath-empty>, which is "same-document reference" (see Section 4.4
+   of [URI-GEN]).
+
+   The following observations about relative URLs are important:
+
+   The <iauth> grammar element (which is a part of <iuserinfo>, which
+   is, in turn, a part of <iserver>; see Section 3) is considered part
+   of the user name for purposes of resolving relative IMAP URLs.  This
+   means that unless a new user name/server specification is included in
+   the relative URL, the authentication mechanism is inherited from the
+   base IMAP URL.
+
+   URLs always use "/" as the hierarchy delimiter for the purpose of
+   resolving paths in relative URLs.  IMAP4 permits the use of any
+   hierarchy delimiter in mailbox names.  For this reason, relative
+   mailbox paths will only work if the mailbox uses "/" as the hierarchy
+   delimiter.  Relative URLs may be used on mailboxes that use other
+   delimiters, but in that case, the entire mailbox name MUST be
+   specified in the relative URL or inherited as a whole from the base
+   URL.
+
+   If an IMAP server allows for mailbox names starting with "./" or
+   "../", ending with "/." or "/..", or containing sequences "/../" or
+   "/./", then such mailbox names MUST be percent-encoded as described
+   in [URI-GEN].  Otherwise, they would be misinterpreted as dot-
+   segments (see Section 3.3 of [URI-GEN]), which are processed
+   specially during the relative path resolution process.
+
+7.1.  absolute-path References
+
+   A relative reference that begins with a single slash character is
+   termed an absolute-path reference (see Section 4.2 of [URI-GEN]).  If
+   an IMAP server permits mailbox names with a leading "/", then the
+   leading "/" MUST be percent-encoded as described in [URI-GEN].
+   Otherwise, the produced absolute-path reference URI will be
+   misinterpreted as a network-path reference [URI-GEN] described by the
+   <inetwork-path> non-terminal.
+
+7.2.  relative-path References
+
+   A relative reference that does not begin with a slash character is
+   termed a relative-path reference [URI-GEN].  Implementations MUST NOT
+   generate or accept relative-path IMAP references.
+
+   See also Section 4.2 of [URI-GEN] for restrictions on relative-path
+   references.
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 12]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+8.  Internationalization Considerations
+
+   IMAP4, Section 5.1.3 [IMAP4] includes a convention for encoding non-
+   US-ASCII characters in IMAP mailbox names.  Because this convention
+   is private to IMAP, it is necessary to convert IMAP's encoding to one
+   that can be more easily interpreted by a URL display program.  For
+   this reason, IMAP's modified UTF-7 encoding for mailboxes MUST be
+   converted to UTF-8 [UTF-8].  Since 8-bit octets are not permitted in
+   URLs, the UTF-8 octets are percent-encoded as required by the URL
+   specification [URI-GEN], Section 2.1.  Sample code is included in
+   Appendix A to demonstrate this conversion.
+
+   IMAP user names are UTF-8 strings and MUST be percent-encoded as
+   required by the URL specification [URI-GEN], Section 2.1.
+
+   Also note that IMAP SEARCH criteria can contain non-US-ASCII
+   characters.  8-bit octets in those strings MUST be percent-encoded as
+   required by the URL specification [URI-GEN], Section 2.1.
+
+9.  Examples
+
+   The following examples demonstrate how an IMAP4 client program might
+   translate various IMAP4 URLs into a series of IMAP4 commands.
+   Commands sent from the client to the server are prefixed with "C:",
+   and responses sent from the server to the client are prefixed with
+   "S:".
+
+   The URL:
+
+      <imap://minbari.example.org/gray-council;UIDVALIDITY=385759045/;
+      UID=20/;PARTIAL=0.1024>
+
+   may result in the following client commands and server responses:
+
+      <connect to minbari.example.org, port 143>
+      S: * OK [CAPABILITY IMAP4rev1 STARTTLS AUTH=ANONYMOUS] Welcome
+      C: A001 AUTHENTICATE ANONYMOUS
+      S: +
+      C: c2hlcmlkYW5AYmFieWxvbjUuZXhhbXBsZS5vcmc=
+      S: A001 OK Welcome sheridan@babylon5.example.org
+      C: A002 SELECT gray-council
+      <client verifies the UIDVALIDITY matches>
+      C: A003 UID FETCH 20 BODY.PEEK[]<0.1024>
+
+   The URL:
+
+      <imap://psicorp.example.org/~peter/%E6%97%A5%E6%9C%AC%E8%AA%9E/
+      %E5%8F%B0%E5%8C%97>
+
+
+
+Melnikov & Newman           Standards Track                    [Page 13]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   may result in the following client commands:
+
+      <connect to psicorp.example.org, port 143>
+      S: * OK [CAPABILITY IMAP4rev1 STARTTLS AUTH=CRAM-MD5] Welcome
+      C: A001 LOGIN ANONYMOUS bester@psycop.psicorp.example.org
+      C: A002 SELECT ~peter/&ZeVnLIqe-/&U,BTFw-
+      <commands the client uses for viewing the contents of
+       the mailbox>
+
+   The URL:
+
+      <imap://;AUTH=GSSAPI@minbari.example.org/gray-council/;uid=20/
+      ;section=1.2>
+
+   may result in the following client commands:
+
+      <connect to minbari.example.org, port 143>
+      S: * OK Greetings
+      C: A000 CAPABILITY
+      S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI
+      S: A000 OK
+      C: A001 AUTHENTICATE GSSAPI
+      <authentication exchange>
+      C: A002 SELECT gray-council
+      C: A003 UID FETCH 20 BODY.PEEK[1.2]
+
+   If the following relative URL is located in that body part:
+
+      <;section=1.4>
+
+   this could result in the following client commands:
+
+      C: A004 UID FETCH 20 (BODY.PEEK[1.2.MIME]
+            BODY.PEEK[1.MIME]
+            BODY.PEEK[HEADER.FIELDS (Content-Location)])
+      <Client looks for Content-Location headers in
+       result.  If no such headers, then it does the following>
+      C: A005 UID FETCH 20 BODY.PEEK[1.4]
+
+   The URL:
+
+      <imap://;AUTH=*@minbari.example.org/gray%20council?
+      SUBJECT%20shadows>
+
+
+
+
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 14]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   could result in the following:
+
+      <connect to minbari.example.org, port 143>
+      S: * OK Welcome
+      C: A001 CAPABILITY
+      S: * CAPABILITY IMAP4rev1 AUTH=DIGEST-MD5
+      S: A001 OK
+      C: A002 AUTHENTICATE DIGEST-MD5
+      <authentication exchange>
+      S: A002 OK user lennier authenticated
+      C: A003 SELECT "gray council"
+      ...
+      C: A004 SEARCH SUBJECT shadows
+      S: * SEARCH 8 10 13 14 15 16
+      S: A004 OK SEARCH completed
+      C: A005 FETCH 8,10,13:16 ALL
+      ...
+
+   In the example above, the client has implementation-dependent
+   choices.  The authentication mechanism could be anything, including
+   PREAUTH.  The final FETCH command could fetch more or less
+   information about the messages, depending on what it wishes to
+   display to the user.
+
+   The URL:
+
+      <imap://john;AUTH=*@minbari.example.org/babylon5/personel?
+      charset%20UTF-8%20SUBJECT%20%7B14+%7D%0D%0A%D0%98%D0%B2%
+      D0%B0%D0%BD%D0%BE%D0%B2%D0%B0>
+
+   shows that 8-bit data can be sent using non-synchronizing literals
+   [LITERAL+].  This could result in the following:
+
+      <connect to minbari.example.org, port 143>
+      S: * OK Hi there
+      C: A001 CAPABILITY
+      S: * CAPABILITY IMAP4rev1 LITERAL+ AUTH=DIGEST-MD5
+      S: A001 OK
+      C: A002 AUTHENTICATE DIGEST-MD5
+      <authentication exchange>
+      S: A002 OK user john authenticated
+      C: A003 SELECT babylon5/personel
+      ...
+      C: A004 SEARCH CHARSET UTF-8 SUBJECT {14+}
+      C: XXXXXXXXXXXXXX
+      S: * SEARCH 7 10 12
+      S: A004 OK SEARCH completed
+      C: A005 FETCH 7,10,12 ALL
+
+
+
+Melnikov & Newman           Standards Track                    [Page 15]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+      ...
+
+   where XXXXXXXXXXXXXX is 14 bytes of UTF-8 encoded data as specified
+   in the URL above.
+
+9.1.  Examples of Relative URLs
+
+   The following absolute-path reference
+
+      </foo/;UID=20/..>
+
+   is the same as
+
+      </foo>
+
+   That is, both of them reference the mailbox "foo" located on the IMAP
+   server described by the corresponding Base URI.
+
+   The following relative-path reference
+
+      <;UID=20>
+
+   references a message with UID in the mailbox specified by the Base
+   URI.
+
+   The following edge case example demonstrates that the ;UIDVALIDITY=
+   modifier is a part of the mailbox name as far as relative URI
+   resolution is concerned:
+
+      <..;UIDVALIDITY=385759045/;UID=20>
+
+   In this example, ".." is not a dot-segment [URI-GEN].
+
+10.  Security Considerations
+
+   Security considerations discussed in the IMAP specification [IMAP4]
+   and the URI specification [URI-GEN] are relevant.  Security
+   considerations related to authenticated URLs are discussed in Section
+   3.2 of this document.
+
+   Many email clients store the plaintext password for later use after
+   logging into an IMAP server.  Such clients MUST NOT use a stored
+   password in response to an IMAP URL without explicit permission from
+   the user to supply that password to the specified host name.
+
+   Clients resolving IMAP URLs that wish to achieve data confidentiality
+   and/or integrity SHOULD use the STARTTLS command (if supported by the
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 16]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   server) before starting authentication, or use a SASL mechanism, such
+   as GSSAPI, that provides a confidentiality security layer.
+
+10.1.  Security Consideration Specific to URLAUTH Authorized URL
+
+   The "user+<userid>" <access> identifier limits resolution of that URL
+   to a particular userid, whereas the "submit+<userid>" <access>
+   identifier is more general and simply requires that the session be
+   authorized by a user that has been granted a "submit" role within the
+   authentication system.  Use of either of these mechanisms limits the
+   scope of the URL.  An attacker who cannot authenticate using the
+   appropriate credentials cannot make use of the URL.
+
+   The "authuser" and "anonymous" <access> identifiers do not have this
+   level of protection.  These access identifiers are primarily useful
+   for public export of data from an IMAP server, without requiring that
+   it be copied to a web or anonymous FTP server.
+
+   The decision to use the "authuser" <access> identifier should be made
+   with caution.  An "authuser" <access> identifier can be used by any
+   authorized user of the IMAP server; therefore, use of this access
+   identifier should be limited to content that may be disclosed to any
+   authorized user of the IMAP server.
+
+   The decision to use the "anonymous" <access> identifier should be
+   made with extreme caution.  An "anonymous" <access> identifier can be
+   used by anyone; therefore, use of this access identifier should be
+   limited to content that may be disclosed to anyone.
+
+11.  ABNF for IMAP URL Scheme
+
+   Formal syntax is defined using ABNF [ABNF], extending the ABNF rules
+   in Section 9 of [IMAP4].  Elements not defined here can be found in
+   [ABNF], [IMAP4], [IMAPABNF], or [URI-GEN].  Strings are not case
+   sensitive, and free insertion of linear white space is not permitted.
+
+   sub-delims-sh = "!" / "$" / "'" / "(" / ")" /
+                   "*" / "+" / ","
+                      ;; Same as [URI-GEN] sub-delims,
+                      ;; but without ";", "&" and "=".
+
+   uchar            = unreserved / sub-delims-sh / pct-encoded
+
+   achar            = uchar / "&" / "="
+                      ;; Same as [URI-GEN] 'unreserved / sub-delims /
+                      ;; pct-encoded', but ";" is disallowed.
+
+   bchar            = achar / ":" / "@" / "/"
+
+
+
+Melnikov & Newman           Standards Track                    [Page 17]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   enc-auth-type    = 1*achar
+                   ; %-encoded version of [IMAP4] "auth-type"
+
+   enc-mailbox      = 1*bchar
+                  ; %-encoded version of [IMAP4] "mailbox"
+
+   enc-search       = 1*bchar
+                           ; %-encoded version of [IMAPABNF]
+                           ; "search-program".  Note that IMAP4
+                           ; literals may not be used in
+                           ; a "search-program", i.e., only
+                           ; quoted or non-synchronizing
+                           ; literals (if the server supports
+                           ; LITERAL+ [LITERAL+]) are allowed.
+
+   enc-section      = 1*bchar
+                  ; %-encoded version of [IMAP4] "section-spec"
+
+   enc-user         = 1*achar
+                  ; %-encoded version of [IMAP4] authorization
+                  ; identity or "userid".
+
+   imapurl          = "imap://" iserver ipath-query
+               ; Defines an absolute IMAP URL
+
+   ipath-query      = ["/" [ icommand ]]
+                    ; Corresponds to "path-abempty [ "?" query ]"
+                    ; in [URI-GEN]
+
+   Generic syntax for relative URLs is defined in Section 4.2 of
+   [URI-GEN].  For ease of implementation, the relative IMAP URL syntax
+   is defined below:
+
+   imapurl-rel     = inetwork-path
+
+                     / iabsolute-path
+                     / irelative-path
+                     / ipath-empty
+
+   inetwork-path   = "//" iserver ipath-query
+               ; Corresponds to '"//" authority path-abempty
+               ; [ "?" query ]' in [URI-GEN]
+
+   iabsolute-path  = "/" [ icommand ]
+               ; icommand, if present, MUST NOT start with '/'.
+               ;
+               ; Corresponds to 'path-absolute [ "?" query ]'
+               ; in [URI-GEN]
+
+
+
+Melnikov & Newman           Standards Track                    [Page 18]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   irelative-path  = imessagelist /
+                     imsg-or-part
+               ; Corresponds to 'path-noscheme [ "?" query ]'
+               ; in [URI-GEN]
+
+   imsg-or-part    = ( imailbox-ref "/" iuid-only ["/" isection-only]
+                       ["/" ipartial-only] ) /
+                     ( iuid-only ["/" isection-only]
+                       ["/" ipartial-only] ) /
+                     ( isection-only ["/" ipartial-only] ) /
+                     ipartial-only
+
+   ipath-empty     = 0<pchar>
+                    ; Zero characters.
+                    ; The same-document reference.
+
+   The following three rules are only used in the presence of the IMAP
+   [URLAUTH] extension:
+
+   authimapurl     = "imap://" iserver "/" imessagepart
+                     ; Same as "imapurl" when "[icommand]" is
+                     ; "imessagepart"
+
+   authimapurlfull = authimapurl iurlauth
+                     ; Same as "imapurl" when "[icommand]" is
+                     ; "imessagepart iurlauth"
+
+   authimapurlrump = authimapurl iurlauth-rump
+
+
+   enc-urlauth     = 32*HEXDIG
+
+   iurlauth        = iurlauth-rump iua-verifier
+
+   iua-verifier    = ":" uauth-mechanism ":" enc-urlauth
+
+   iurlauth-rump   = [expire] ";URLAUTH=" access
+
+   access          = ("submit+" enc-user) / ("user+" enc-user) /
+                       "authuser" / "anonymous"
+
+   expire          = ";EXPIRE=" date-time
+                         ; date-time is defined in [DATETIME]
+
+   uauth-mechanism = "INTERNAL" / 1*(ALPHA / DIGIT / "-" / ".")
+                        ; Case-insensitive.
+                        ; New mechanisms MUST be registered with IANA.
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 19]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   iauth            = ";AUTH=" ( "*" / enc-auth-type )
+
+   icommand         = imessagelist /
+                      imessagepart [iurlauth]
+
+   imailbox-ref     = enc-mailbox [uidvalidity]
+
+   imessagelist     = imailbox-ref [ "?" enc-search ]
+                  ; "enc-search" is [URI-GEN] "query".
+
+   imessagepart     = imailbox-ref iuid [isection] [ipartial]
+
+   ipartial         = "/" ipartial-only
+
+   ipartial-only    = ";PARTIAL=" partial-range
+
+   isection         = "/" isection-only
+
+   isection-only    = ";SECTION=" enc-section
+
+   iserver          = [iuserinfo "@"] host [ ":" port ]
+                           ; This is the same as "authority" defined
+                           ; in [URI-GEN].  See [URI-GEN] for "host"
+                           ; and "port" definitions.
+
+   iuid             = "/" iuid-only
+
+   iuid-only        = ";UID=" nz-number
+                  ; See [IMAP4] for "nz-number" definition
+
+   iuserinfo        = enc-user [iauth] / [enc-user] iauth
+                                ; conforms to the generic syntax of
+                                ; "userinfo" as defined in [URI-GEN].
+
+   partial-range    = number ["." nz-number]
+                  ; partial FETCH.  The first number is
+                           ; the offset of the first byte,
+                           ; the second number is the length of
+                           ; the fragment.
+
+   uidvalidity      = ";UIDVALIDITY=" nz-number
+                       ; See [IMAP4] for "nz-number" definition
+
+
+
+
+
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 20]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+12.  IANA Considerations
+
+   IANA has updated the "imap" definition in the "Uniform Resource
+   Identifier scheme registry" to point to this document.
+
+   The registration template (as per [URI-REG]) is specified in Section
+   12.1 of this document.
+
+12.1.  IANA Registration of imap: URI Scheme
+
+   This section provides the information required to register the imap:
+   URI scheme.
+
+   URI scheme name: imap
+
+   Status: permanent
+
+   URI scheme syntax:
+
+      See Section 11 of [RFC5092].
+
+   URI scheme semantics:
+
+      The imap: URI scheme is used to designate IMAP servers, mailboxes,
+      messages, MIME bodies [MIME] and their parts, and search programs
+      on Internet hosts accessible using the IMAP protocol.
+
+      There is no MIME type associated with this URI.
+
+   Encoding considerations:
+
+      See Section 8 of [RFC5092].
+
+   Applications/protocols that use this URI scheme name:
+
+      The imap: URI is intended to be used by applications that might
+      need access to an IMAP mailstore.  Such applications may include
+      (but are not limited to) IMAP-capable web browsers; IMAP clients
+      that wish to access a mailbox, message, or edit a message on the
+      server using [CATENATE]; [SUBMIT] clients and servers that are
+      requested to assemble a complete message on submission using
+      [BURL].
+
+   Interoperability considerations:
+
+      A widely deployed IMAP client Netscape Mail (and possibly
+      Mozilla/Thunderbird/Seamonkey) uses a different imap: scheme
+      internally.
+
+
+
+Melnikov & Newman           Standards Track                    [Page 21]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   Security considerations:
+
+      See Security Considerations (Section 10) of [RFC5092].
+
+   Contact:
+
+      Alexey Melnikov <alexey.melnikov@isode.com>
+
+   Author/Change controller:
+
+      IESG
+
+   References:
+
+      [RFC5092] and [IMAP4].
+
+13. References
+
+13.1.  Normative References
+
+   [KEYWORDS]   Bradner, S., "Key words for use in RFCs to Indicate
+                Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [IMAP4]      Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+                4rev1", RFC 3501, March 2003.
+
+   [IMAPABNF]   Melnikov, A. and C. Daboo, "Collected Extensions to
+                IMAP4 ABNF", RFC 4466, April 2006.
+
+   [ABNF]       Crocker, D., Ed., and P. Overell, "Augmented BNF for
+                Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+   [MIME]       Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+                Extensions (MIME) Part One: Format of Internet Message
+                Bodies", RFC 2045, November 1996.
+
+   [URI-GEN]    Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
+                Resource Identifier (URI): Generic Syntax", STD 66, RFC
+                3986, January 2005.
+
+   [UTF-8]      Yergeau, F., "UTF-8, a transformation format of ISO
+                10646", STD 63, RFC 3629, November 2003.
+
+   [NAMESPACE]  Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
+                May 1998.
+
+   [LITERAL+]   Myers, J., "IMAP4 non-synchronizing literals", RFC 2088,
+                January 1997.
+
+
+
+Melnikov & Newman           Standards Track                    [Page 22]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+   [ANONYMOUS]  Zeilenga, K., "Anonymous Simple Authentication and
+                Security Layer (SASL) Mechanism", RFC 4505, June 2006.
+
+   [DATETIME]   Klyne, G. and C. Newman, "Date and Time on the Internet:
+                Timestamps", RFC 3339, July 2002.
+
+   [URLAUTH]    Crispin, M., "Internet Message Access Protocol (IMAP) -
+                URLAUTH Extension", RFC 4467, May 2006.
+
+13.2.  Informative References
+
+   [SUBMIT]     Gellens, R. and J. Klensin, "Message Submission for
+                Mail", RFC 4409, April 2006.
+
+   [BURL]       Newman, C., "Message Submission BURL Extension", RFC
+                4468, May 2006.
+
+   [CATENATE]   Resnick, P., "Internet Message Access Protocol (IMAP)
+                CATENATE Extension", RFC 4469, April 2006.
+
+   [SASL]       Melnikov, A., Ed., and K. Zeilenga, Ed., "Simple
+                Authentication and Security Layer (SASL)", RFC 4422,
+                June 2006.
+
+   [GSSAPI]     Melnikov, A., Ed., "The Kerberos V5 ("GSSAPI") Simple
+                Authentication and Security Layer (SASL) Mechanism", RFC
+                4752, November 2006.
+
+   [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest Authentication as
+                a SASL Mechanism", RFC 2831, May 2000.
+
+   [URI-REG]    Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
+                Registration Procedures for New URI Schemes", BCP 115,
+                RFC 4395, February 2006.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 23]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+Appendix A.  Sample Code
+
+   Here is sample C source code to convert between URL paths and IMAP
+   mailbox names, taking into account mapping between IMAP's modified
+   UTF-7 [IMAP4] and hex-encoded UTF-8, which is more appropriate for
+   URLs.  This code has not been rigorously tested nor does it
+   necessarily behave reasonably with invalid input, but it should serve
+   as a useful example.  This code just converts the mailbox portion of
+   the URL and does not deal with parameters, query, or server
+   components of the URL.
+
+/* Copyright (C) The IETF Trust (2007).  This version of
+   sample C code is part of RFC XXXX; see the RFC itself
+   for full legal notices.
+
+   Regarding this sample C code (or any portion of it), the authors
+   make no guarantees and are not responsible for any damage
+   resulting from its use.  The authors grant irrevocable permission
+   to anyone to use, modify, and distribute it in any way that does
+   not diminish the rights of anyone else to use, modify, and
+   distribute it, provided that redistributed derivative works do
+   not contain misleading author or version information.
+
+   Derivative works need not be licensed under similar terms.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+/* hexadecimal lookup table */
+static const char hex[] = "0123456789ABCDEF";
+
+#define XX 127
+/*
+ * Table for decoding hexadecimal in %encoding
+ */
+static const char index_hex[256] = {
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+     0, 1, 2, 3,  4, 5, 6, 7,  8, 9,XX,XX, XX,XX,XX,XX,
+    XX,10,11,12, 13,14,15,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,10,11,12, 13,14,15,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+
+
+
+Melnikov & Newman           Standards Track                    [Page 24]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+};
+#define HEXCHAR(c)  (index_hex[(unsigned char)(c)])
+
+/* "gen-delims" excluding "/" but including "%" */
+#define GENERAL_DELIMS_NO_SLASH     ":?#[]@" "%"
+
+/* "gen-delims" (excluding "/", but including "%")
+   plus subset of "sub-delims" */
+#define GENERAL_UNSAFE_NO_SLASH     GENERAL_DELIMS_NO_SLASH ";&=+"
+#define OTHER_UNSAFE                " \"<>\\^`{|}"
+
+/* URL unsafe printable characters */
+static const char mailbox_url_unsafe[] = GENERAL_UNSAFE_NO_SLASH
+                                         OTHER_UNSAFE;
+
+/* UTF7 modified base64 alphabet */
+static const char base64chars[] =
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
+
+#define UNDEFINED 64
+
+/* UTF16 definitions */
+#define UTF16MASK   0x03FFUL
+#define UTF16SHIFT  10
+#define UTF16BASE   0x10000UL
+#define UTF16HIGHSTART   0xD800UL
+#define UTF16HIGHEND     0xDBFFUL
+#define UTF16LOSTART     0xDC00UL
+#define UTF16LOEND  0xDFFFUL
+
+/* Convert an IMAP mailbox to a URL path
+ *  dst needs to have roughly 4 times the storage space of src
+ *    Hex encoding can triple the size of the input
+ *    UTF-7 can be slightly denser than UTF-8
+ *     (worst case: 8 octets UTF-7 becomes 9 octets UTF-8)
+ */
+void MailboxToURL(char *dst, char *src)
+{
+    unsigned char c, i, bitcount;
+    unsigned long ucs4, utf16, bitbuf;
+    unsigned char base64[256], utf8[6];
+
+    /* initialize modified base64 decoding table */
+
+
+
+Melnikov & Newman           Standards Track                    [Page 25]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+    memset(base64, UNDEFINED, sizeof (base64));
+    for (i = 0; i < sizeof (base64chars); ++i) {
+     base64[(int) base64chars[i]] = i;
+    }
+
+    /* loop until end of string */
+    while (*src != '\0') {
+     c = *src++;
+     /* deal with literal characters and &- */
+     if (c != '&' || *src == '-') {
+         /* NB: There are no "URL safe" characters after the '~' */
+         if (c < ' ' || c > '~' ||
+             strchr(mailbox_url_unsafe, c) != NULL) {
+          /* hex encode if necessary */
+          dst[0] = '%';
+          dst[1] = hex[c >> 4];
+          dst[2] = hex[c & 0x0f];
+          dst += 3;
+         } else {
+          /* encode literally */
+          *dst++ = c;
+         }
+         /* skip over the '-' if this is an &- sequence */
+         if (c == '&') ++src;
+
+     } else {
+        /* convert modified UTF-7 -> UTF-16 -> UCS-4 -> UTF-8 -> HEX */
+         bitbuf = 0;
+         bitcount = 0;
+         ucs4 = 0;
+         while ((c = base64[(unsigned char) *src]) != UNDEFINED) {
+          ++src;
+          bitbuf = (bitbuf << 6) | c;
+          bitcount += 6;
+          /* enough bits for a UTF-16 character? */
+          if (bitcount >= 16) {
+              bitcount -= 16;
+              utf16 = (bitcount ? bitbuf >> bitcount
+                             : bitbuf) & 0xffff;
+              /* convert UTF16 to UCS4 */
+              if
+                    (utf16 >= UTF16HIGHSTART && utf16 <= UTF16HIGHEND) {
+               ucs4 = (utf16 - UTF16HIGHSTART) << UTF16SHIFT;
+               continue;
+              } else if
+                    (utf16 >= UTF16LOSTART && utf16 <= UTF16LOEND) {
+               ucs4 += utf16 - UTF16LOSTART + UTF16BASE;
+              } else {
+
+
+
+Melnikov & Newman           Standards Track                    [Page 26]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+               ucs4 = utf16;
+              }
+              /* convert UTF-16 range of UCS4 to UTF-8 */
+              if (ucs4 <= 0x7fUL) {
+               utf8[0] = (unsigned char) ucs4;
+               i = 1;
+              } else if (ucs4 <= 0x7ffUL) {
+               utf8[0] = 0xc0 | (unsigned char) (ucs4 >> 6);
+               utf8[1] = 0x80 | (unsigned char) (ucs4 & 0x3f);
+               i = 2;
+              } else if (ucs4 <= 0xffffUL) {
+               utf8[0] = 0xe0 | (unsigned char) (ucs4 >> 12);
+               utf8[1] = 0x80 | (unsigned char) ((ucs4 >> 6) & 0x3f);
+               utf8[2] = 0x80 | (unsigned char) (ucs4 & 0x3f);
+               i = 3;
+              } else {
+               utf8[0] = 0xf0 | (unsigned char) (ucs4 >> 18);
+               utf8[1] = 0x80 | (unsigned char) ((ucs4 >> 12) & 0x3f);
+               utf8[2] = 0x80 | (unsigned char) ((ucs4 >> 6) & 0x3f);
+               utf8[3] = 0x80 | (unsigned char) (ucs4 & 0x3f);
+               i = 4;
+              }
+              /* convert utf8 to hex */
+              for (c = 0; c < i; ++c) {
+               dst[0] = '%';
+               dst[1] = hex[utf8[c] >> 4];
+               dst[2] = hex[utf8[c] & 0x0f];
+               dst += 3;
+              }
+          }
+         }
+         /* skip over trailing '-' in modified UTF-7 encoding */
+         if (*src == '-') ++src;
+     }
+    }
+    /* terminate destination string */
+    *dst = '\0';
+}
+
+/* Convert hex coded UTF-8 URL path to modified UTF-7 IMAP mailbox
+ *  dst should be about twice the length of src to deal with non-hex
+ *  coded URLs
+ */
+int URLtoMailbox(char *dst, char *src)
+{
+    unsigned int utf8pos = 0;
+    unsigned int utf8total, i, c, utf7mode, bitstogo, utf16flag;
+    unsigned long ucs4 = 0, bitbuf = 0;
+
+
+
+Melnikov & Newman           Standards Track                    [Page 27]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+    utf7mode = 0; /* is the output UTF7 currently in base64 mode? */
+    utf8total = 0; /* how many octets is the current input UTF-8 char;
+                      0 == between characters */
+    bitstogo = 0; /* bits that need to be encoded into base64; if
+                     bitstogo != 0 then utf7mode == 1 */
+    while ((c = (unsigned char)*src) != '\0') {
+     ++src;
+     /* undo hex-encoding */
+     if (c == '%' && src[0] != '\0' && src[1] != '\0') {
+         c = HEXCHAR(src[0]);
+         i = HEXCHAR(src[1]);
+         if (c == XX || i == XX) {
+             return 0;
+         } else {
+             c = (char)((c << 4) | i);
+         }
+         src += 2;
+     }
+     /* normal character? */
+     if (c >= ' ' && c <= '~') {
+         /* switch out of UTF-7 mode */
+         if (utf7mode) {
+          if (bitstogo) {
+          *dst++ = base64chars[(bitbuf << (6 - bitstogo)) & 0x3F];
+          }
+          *dst++ = '-';
+          utf7mode = 0;
+          bitstogo = bitbuf = 0;
+         }
+         *dst++ = c;
+         /* encode '&' as '&-' */
+         if (c == '&') {
+          *dst++ = '-';
+         }
+         continue;
+     }
+     /* switch to UTF-7 mode */
+     if (!utf7mode) {
+         *dst++ = '&';
+         utf7mode = 1;
+     }
+     /* Encode US-ASCII characters as themselves */
+     if (c < 0x80) {
+         ucs4 = c;
+         utf8total = 1;
+     } else if (utf8total) {
+         /* this is a subsequent octet of a multi-octet character */
+         /* save UTF8 bits into UCS4 */
+
+
+
+Melnikov & Newman           Standards Track                    [Page 28]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+         ucs4 = (ucs4 << 6) | (c & 0x3FUL);
+         if (++utf8pos < utf8total) {
+          continue;
+         }
+     } else {
+         /* this is the first octet of a multi-octet character */
+         utf8pos = 1;
+         if (c < 0xE0) {
+          utf8total = 2;
+          ucs4 = c & 0x1F;
+         } else if (c < 0xF0) {
+          utf8total = 3;
+          ucs4 = c & 0x0F;
+         } else {
+          /* NOTE: can't convert UTF8 sequences longer than 4 */
+          utf8total = 4;
+          ucs4 = c & 0x03;
+         }
+         continue;
+     }
+     /* Finished with UTF-8 character.  Make sure it isn't an
+        overlong sequence.  If it is, return failure. */
+     if ((ucs4 < 0x80 && utf8total > 1) ||
+         (ucs4 < 0x0800 && utf8total > 2) ||
+         (ucs4 < 0x00010000 && utf8total > 3) ||
+         (ucs4 < 0x00200000 && utf8total > 4) ||
+         (ucs4 < 0x04000000 && utf8total > 5) ||
+         (ucs4 < 0x80000000 && utf8total > 6)) {
+         return 0;
+     }
+     /* loop to split ucs4 into two utf16 chars if necessary */
+     utf8total = 0;
+     do {
+         if (ucs4 >= UTF16BASE) {
+                ucs4 -= UTF16BASE;
+          bitbuf = (bitbuf << 16) | ((ucs4 >> UTF16SHIFT)
+                            + UTF16HIGHSTART);
+          ucs4 = (ucs4 & UTF16MASK) + UTF16LOSTART;
+          utf16flag = 1;
+         } else {
+          bitbuf = (bitbuf << 16) | ucs4;
+          utf16flag = 0;
+         }
+         bitstogo += 16;
+         /* spew out base64 */
+         while (bitstogo >= 6) {
+          bitstogo -= 6;
+          *dst++ = base64chars[(bitstogo ? (bitbuf >> bitstogo)
+
+
+
+Melnikov & Newman           Standards Track                    [Page 29]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+                               : bitbuf)
+                         & 0x3F];
+         }
+     } while (utf16flag);
+    }
+    /* if in UTF-7 mode, finish in ASCII */
+    if (utf7mode) {
+     if (bitstogo) {
+         *dst++ = base64chars[(bitbuf << (6 - bitstogo)) & 0x3F];
+     }
+     *dst++ = '-';
+    }
+    /* tie off string */
+    *dst = '\0';
+    return 1;
+}
+
+Appendix B.  List of Changes since RFC 2192
+
+   Updated boilerplate, list of editor's, etc.
+   Updated references.
+   Updated ABNF not to use _, to use SP instead of SPACE, etc.
+   Updated example domains to use example.org.
+   Fixed ABNF error in "imessagelist" non-terminal.
+   Updated ABNF, due to changes in RFC 3501, RFC 4466, and RFC 3986.
+   Renamed "iuserauth" non-terminal to <iuserinfo>.
+   Clarified that the userinfo component describes both authorization
+   identity and mailbox naming scope.
+   Allow for non-synchronizing literals in "enc-search".
+   Added "ipartial" specifier that denotes a partial FETCH.
+   Moved URLAUTH text from RFC 4467 to this document.
+   Updated ABNF for the whole server to allow missing trailing "/"
+   (e.g., "imap://imap.example.com" is now valid and is the same as
+   "imap://imap.example.com/").
+   Clarified how relative-path references are constructed.
+   Added more examples demonstrating relative-path references.
+   Added rules for relative URLs and restructured ABNF as the result.
+   Removed text on use of relative URLs in MHTML.
+   Added examples demonstrating security considerations when resolving
+   URLs.
+   Recommend usage of STARTTLS/SASL security layer to protect
+   confidential data.
+   Removed some advices about connection reuse that were incorrect.
+   Removed URLs referencing a list of mailboxes, as this feature
+   hasn't seen any deployments.
+   Clarified that user name "anonymous" is case-insensitive.
+
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 30]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+Appendix C.  List of Changes since RFC 4467
+
+   Renamed <mechanism> to <uauth-mechanism>.  Restructured ABNF.
+
+Appendix D.  Acknowledgments
+
+   Text describing URLAUTH was lifted from [URLAUTH] by Mark Crispin.
+
+   Stephane H. Maes contributed some ideas to this document; he also
+   co-edited early versions of this document.
+
+   The editors would like to thank Mark Crispin, Ken Murchison, Ted
+   Hardie, Zoltan Ordogh, Dave Cridland, Kjetil Torgrim Homme, Lisa
+   Dusseault, Spencer Dawkins, Filip Navara, Shawn M. Emery, Sam
+   Hartman, Russ Housley, and Lars Eggert for the time they devoted to
+   reviewing this document and/or for the comments received.
+
+Authors' Addresses
+
+   Chris Newman (Author/Editor)
+   Sun Microsystems
+   3401 Centrelake Dr., Suite 410
+   Ontario, CA 91761
+   EMail: chris.newman@sun.com
+
+   Alexey Melnikov (Editor)
+   Isode Limited
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex
+   TW12 2BX, UK
+   EMail: Alexey.Melnikov@isode.com
+   URI:   http://www.melnikov.ca/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 31]
+
+RFC 5092                    IMAP URL Scheme                November 2007
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2007).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Newman           Standards Track                    [Page 32]
+
diff --git a/imap/docs/rfc/rfc5161.txt b/imap/docs/rfc/rfc5161.txt
new file mode 100644
index 00000000..13bbbf74
--- /dev/null
+++ b/imap/docs/rfc/rfc5161.txt
@@ -0,0 +1,395 @@
+
+
+
+
+
+
+Network Working Group                                A. Gulbrandsen, Ed.
+Request for Comments: 5161                        Oryx Mail Systems GmbH
+Category: Standards Track                               A. Melnikov, Ed.
+                                                           Isode Limited
+                                                              March 2008
+
+
+                       The IMAP ENABLE Extension
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   Most IMAP extensions are used by the client when it wants to and the
+   server supports it.  However, a few extensions require the server to
+   know whether a client supports that extension.  The ENABLE extension
+   allows an IMAP client to say which extensions it supports.
+
+1.  Overview
+
+   Several IMAP extensions allow the server to return unsolicited
+   responses specific to these extensions in certain circumstances.
+   However, servers cannot send those unsolicited responses until they
+   know that the clients support such extensions and thus won't choke on
+   the extension response data.
+
+   Up until now, extensions have typically stated that a server cannot
+   send the unsolicited responses until after the client has used a
+   command with the extension data (i.e., at that point the server knows
+   the client is aware of the extension).  CONDSTORE ([RFC4551]),
+   ANNOTATE ([ANNOTATE]), and some extensions under consideration at the
+   moment use various commands to enable server extensions.  For
+   example, CONDSTORE uses a SELECT or FETCH parameter, and ANNOTATE
+   uses a side effect of FETCH.
+
+   The ENABLE extension provides an explicit indication from the client
+   that it supports particular extensions.  This is done using a new
+   ENABLE command.
+
+   An IMAP server that supports ENABLE advertises this by including the
+   word ENABLE in its capability list.
+
+
+
+
+Gulbrandsen & Melnikov      Standards Track                     [Page 1]
+
+RFC 5161               The IMAP ENABLE Extension              March 2008
+
+
+   Most IMAP extensions do not require the client to enable the
+   extension in any way.
+
+2.  Conventions Used in This Document
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC2119].
+
+   Formal syntax is defined by [RFC5234] and [RFC3501].
+
+   Example lines prefaced by "C:" are sent by the client and ones
+   prefaced by "S:" by the server.  The five characters [...] means that
+   something has been elided.
+
+3.  Protocol Changes
+
+3.1.  The ENABLE Command
+
+   Arguments: capability names
+
+   Result:    OK: Relevant capabilities enabled
+              BAD: No arguments, or syntax error in an argument
+
+   The ENABLE command takes a list of capability names, and requests the
+   server to enable the named extensions.  Once enabled using ENABLE,
+   each extension remains active until the IMAP connection is closed.
+   For each argument, the server does the following:
+
+   - If the argument is not an extension known to the server, the server
+     MUST ignore the argument.
+
+   - If the argument is an extension known to the server, and it is not
+     specifically permitted to be enabled using ENABLE, the server MUST
+     ignore the argument.  (Note that knowing about an extension doesn't
+     necessarily imply supporting that extension.)
+
+   - If the argument is an extension that is supported by the server and
+     that needs to be enabled, the server MUST enable the extension for
+     the duration of the connection.  At present, this applies only to
+     CONDSTORE ([RFC4551]).  Note that once an extension is enabled,
+     there is no way to disable it.
+
+   If the ENABLE command is successful, the server MUST send an untagged
+   ENABLED response (see Section 3.2).
+
+
+
+
+
+
+Gulbrandsen & Melnikov      Standards Track                     [Page 2]
+
+RFC 5161               The IMAP ENABLE Extension              March 2008
+
+
+   Clients SHOULD only include extensions that need to be enabled by the
+   server.  At the time of publication, CONDSTORE is the only such
+   extension (i.e., ENABLE CONDSTORE is an additional "CONDSTORE
+   enabling command" as defined in [RFC4551]).  Future RFCs may add to
+   this list.
+
+   The ENABLE command is only valid in the authenticated state (see
+   [RFC3501]), before any mailbox is selected.  Clients MUST NOT issue
+   ENABLE once they SELECT/EXAMINE a mailbox; however, server
+   implementations don't have to check that no mailbox is selected or
+   was previously selected during the duration of a connection.
+
+   The ENABLE command can be issued multiple times in a session.  It is
+   additive; i.e., "ENABLE a b", followed by "ENABLE c" is the same as a
+   single command "ENABLE a b c".  When multiple ENABLE commands are
+   issued, each corresponding ENABLED response SHOULD only contain
+   extensions enabled by the corresponding ENABLE command.
+
+   There are no limitations on pipelining ENABLE.  For example, it is
+   possible to send ENABLE and then immediately SELECT, or a LOGIN
+   immediately followed by ENABLE.
+
+   The server MUST NOT change the CAPABILITY list as a result of
+   executing ENABLE; i.e., a CAPABILITY command issued right after an
+   ENABLE command MUST list the same capabilities as a CAPABILITY
+   command issued before the ENABLE command.  This is demonstrated in
+   the following example:
+
+      C: t1 CAPABILITY
+      S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA
+      S: t1 OK foo
+      C: t2 ENABLE CONDSTORE X-GOOD-IDEA
+      S: * ENABLED X-GOOD-IDEA
+      S: t2 OK foo
+      C: t3 CAPABILITY
+      S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA
+      S: t3 OK foo again
+
+   In the following example, the client enables CONDSTORE:
+
+      C: a1 ENABLE CONDSTORE
+      S: * ENABLED CONDSTORE
+      S: a1 OK Conditional Store enabled
+
+
+
+
+
+
+
+
+Gulbrandsen & Melnikov      Standards Track                     [Page 3]
+
+RFC 5161               The IMAP ENABLE Extension              March 2008
+
+
+3.2.  The ENABLED Response
+
+   Contents:   capability listing
+
+   The ENABLED response occurs as a result of an ENABLE command.  The
+   capability listing contains a space-separated listing of capability
+   names that the server supports and that were successfully enabled.
+   The ENABLED response may contain no capabilities, which means that no
+   extensions listed by the client were successfully enabled.
+
+3.3.  Note to Designers of Extensions That May Use the ENABLE Command
+
+   Designers of IMAP extensions are discouraged from creating extensions
+   that require ENABLE unless there is no good alternative design.
+   Specifically, extensions that cause potentially incompatible behavior
+   changes to deployed server responses (and thus benefit from ENABLE)
+   have a higher complexity cost than extensions that do not.
+
+4.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [RFC5234] including the core
+   rules in Appendix B.1.  [RFC3501] defines the non-terminals
+   "capability" and "command-any".
+
+   Except as noted otherwise, all alphabetic characters are
+   case-insensitive.  The use of upper or lower case characters to
+   define token strings is for editorial clarity only.  Implementations
+   MUST accept these strings in a case-insensitive fashion.
+
+      capability    =/ "ENABLE"
+
+      command-any   =/ "ENABLE" 1*(SP capability)
+
+      response-data =/ "*" SP enable-data CRLF
+
+      enable-data   = "ENABLED" *(SP capability)
+
+5.  Security Considerations
+
+   It is believed that this extension doesn't add any security
+   considerations that are not already present in the base IMAP protocol
+   [RFC3501].
+
+6.  IANA Considerations
+
+   The IANA has added ENABLE to the IMAP4 Capabilities Registry.
+
+
+
+
+Gulbrandsen & Melnikov      Standards Track                     [Page 4]
+
+RFC 5161               The IMAP ENABLE Extension              March 2008
+
+
+7.  Acknowledgments
+
+   The editors would like to thank Randy Gellens, Chris Newman, Peter
+   Coates, Dave Cridland, Mark Crispin, Ned Freed, Dan Karp, Cyrus
+   Daboo, Ken Murchison, and Eric Burger for comments and corrections.
+   However, this doesn't necessarily mean that they endorse this
+   extension, agree with all details, or are responsible for errors
+   introduced by the editors.
+
+8.  Normative References
+
+   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC3501]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+              4rev1", RFC 3501, March 2003.
+
+   [RFC5234]  Crocker, D., Ed., and P. Overell, "Augmented BNF for
+              Syntax Specifications: ABNF", STD 68, RFC 5234, January
+              2008.
+
+   [RFC4551]  Melnikov, A. and S. Hole, "IMAP Extension for Conditional
+              STORE Operation or Quick Flag Changes Resynchronization",
+              RFC 4551, June 2006.
+
+9.  Informative References
+
+   [ANNOTATE] Daboo, C. and R. Gellens, "IMAP ANNOTATE Extension", Work
+              in Progress, August 2006.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen & Melnikov      Standards Track                     [Page 5]
+
+RFC 5161               The IMAP ENABLE Extension              March 2008
+
+
+Editors' Addresses
+
+   Arnt Gulbrandsen
+   Oryx Mail Systems GmbH
+   Schweppermannstr. 8
+   D-81671 Muenchen
+   Germany
+
+   Fax: +49 89 4502 9758
+   EMail: arnt@oryx.com
+
+
+   Alexey Melnikov
+   Isode Ltd
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex  TW12 2BX
+   UK
+
+   EMail: Alexey.Melnikov@isode.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen & Melnikov      Standards Track                     [Page 6]
+
+RFC 5161               The IMAP ENABLE Extension              March 2008
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2008).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen & Melnikov      Standards Track                     [Page 7]
+
diff --git a/imap/docs/rfc/rfc5162.txt b/imap/docs/rfc/rfc5162.txt
new file mode 100644
index 00000000..305c54fb
--- /dev/null
+++ b/imap/docs/rfc/rfc5162.txt
@@ -0,0 +1,1291 @@
+
+
+
+
+
+
+Network Working Group                                        A. Melnikov
+Request for Comments: 5162                                   D. Cridland
+Category: Standards Track                                      Isode Ltd
+                                                               C. Wilson
+                                                                   Nokia
+                                                              March 2008
+
+
+          IMAP4 Extensions for Quick Mailbox Resynchronization
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   This document defines an IMAP4 extension, which gives an IMAP client
+   the ability to quickly resynchronize any previously opened mailbox as
+   part of the SELECT command, without the need for server-side state or
+   additional client round-trips.  This extension also introduces a new
+   response that allows for a more compact representation of a list of
+   expunged messages (and always includes the Unique Identifiers (UIDs)
+   expunged).
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                     [Page 1]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+Table of Contents
+
+   1.  Introduction and Overview  . . . . . . . . . . . . . . . . . .  2
+   2.  Requirements Notation  . . . . . . . . . . . . . . . . . . . .  4
+   3.  IMAP Protocol Changes  . . . . . . . . . . . . . . . . . . . .  4
+     3.1.  QRESYNC Parameter to SELECT/EXAMINE  . . . . . . . . . . .  4
+     3.2.  VANISHED UID FETCH Modifier  . . . . . . . . . . . . . . .  8
+     3.3.  EXPUNGE Command  . . . . . . . . . . . . . . . . . . . . . 10
+     3.4.  CLOSE Command  . . . . . . . . . . . . . . . . . . . . . . 11
+     3.5.  UID EXPUNGE Command  . . . . . . . . . . . . . . . . . . . 11
+     3.6.  VANISHED Response  . . . . . . . . . . . . . . . . . . . . 12
+     3.7.  CLOSED Response Code . . . . . . . . . . . . . . . . . . . 15
+   4.  Server Implementation Considerations . . . . . . . . . . . . . 15
+     4.1.  Server Implementations That Don't Store Extra State  . . . 15
+     4.2.  Server Implementations Storing Minimal State . . . . . . . 16
+     4.3.  Additional State Required on the Server  . . . . . . . . . 16
+   5.  Updated Synchronization Sequence . . . . . . . . . . . . . . . 17
+   6.  Formal Syntax  . . . . . . . . . . . . . . . . . . . . . . . . 19
+   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
+   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 21
+   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 21
+   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
+     10.1. Normative References . . . . . . . . . . . . . . . . . . . 21
+     10.2. Informative References . . . . . . . . . . . . . . . . . . 22
+
+1.  Introduction and Overview
+
+   The [CONDSTORE] extension gives a disconnected client the ability to
+   quickly resynchronize IMAP flag changes for previously seen messages.
+   This can be done using the CHANGEDSINCE FETCH modifier once a mailbox
+   is opened.  In order for the client to discover which messages have
+   been expunged, the client still has to issue a UID FETCH or a UID
+   SEARCH command.  This document defines an extension to [CONDSTORE]
+   that allows a reconnecting client to perform full resynchronization,
+   including discovery of expunged messages, in a single round-trip.
+   This extension also introduces a new response, VANISHED, that allows
+   for a more compact representation of a list of expunged messages.
+
+   This extension can be useful for mobile clients that can experience
+   frequent disconnects caused by environmental factors (battery life,
+   signal strength, etc.).  Such clients need a way to quickly reconnect
+   to the IMAP server, while minimizing delay experienced by the user as
+   well as the amount of traffic (and hence the expense) generated by
+   resynchronization.
+
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                     [Page 2]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   By extending the SELECT command to perform the additional
+   resynchronization, this also allows clients to reduce concurrent
+   connections to the IMAP server held purely for the sake of avoiding
+   the resynchronization.
+
+   The quick resync IMAP extension is present if an IMAP4 server returns
+   "QRESYNC" as one of the supported capabilities to the CAPABILITY
+   command.
+
+   Servers supporting this extension MUST implement and advertise
+   support for the [ENABLE] IMAP extension.  Also, the presence of the
+   "QRESYNC" capability implies support for the [CONDSTORE] IMAP
+   extension even if the CONDSTORE capability isn't advertised.  A
+   server compliant with this specification is REQUIREd to support
+   "ENABLE QRESYNC" and "ENABLE QRESYNC CONDSTORE" (which are "CONDSTORE
+   enabling commands", as defined in [CONDSTORE], and have identical
+   results), but there is no requirement for a compliant server to
+   support "ENABLE CONDSTORE" by itself.  The "ENABLE QRESYNC"/"ENABLE
+   QRESYNC CONDSTORE" command also tells the server that it SHOULD start
+   sending VANISHED responses (see Section 3.6) instead of EXPUNGE
+   responses.  This change remains in effect until the connection is
+   closed.
+
+   For compatibility with clients that only support the [CONDSTORE] IMAP
+   extension, servers SHOULD advertise CONDSTORE in the CAPABILITY
+   response as well.
+
+   A client making use of this extension MUST issue "ENABLE QRESYNC"
+   once it is authenticated.  A server MUST respond with a tagged BAD
+   response if the QRESYNC parameter to the SELECT/EXAMINE command or
+   the VANISHED UID FETCH modifier is specified and the client hasn't
+   issued "ENABLE QRESYNC" in the current connection.
+
+   This document puts additional requirements on a server implementing
+   the [CONDSTORE] extension.  Each mailbox that supports persistent
+   storage of mod-sequences, i.e., for which the server has sent a
+   HIGHESTMODSEQ untagged OK response code on a successful SELECT/
+   EXAMINE, MUST increment the per-mailbox mod-sequence when one or more
+   messages are expunged due to EXPUNGE, UID EXPUNGE or CLOSE; the
+   server MUST associate the incremented mod-sequence with the UIDs of
+   the expunged messages.
+
+   A client that supports CONDSTORE but not this extension might
+   resynchronize a mailbox and discover that its HIGHESTMODSEQ has
+   increased from the value cached by the client.  If the increase is
+   only due to messages having been expunged since the client last
+   synchronized, the client is likely to send a FETCH ...  CHANGEDSINCE
+   command that returns no data.  Thus, a client that supports CONDSTORE
+
+
+
+Melnikov, et al.            Standards Track                     [Page 3]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   but not this extension might incur a penalty of an unneeded round-
+   trip when resynchronizing some mailboxes (those that have had
+   messages expunged but no flag changes since the last
+   synchronization).
+
+   This extra round-trip is only incurred by clients that support
+   CONDSTORE but not this extension, and only when a mailbox has had
+   messages expunged but no flag changes to non-expunged messages.
+   Since CONDSTORE is a relatively new extension, it is thought likely
+   that clients that support it will also support this extension.
+
+2.  Requirements Notation
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in [RFC2119].
+
+   In examples, "C:" and "S:" indicate lines sent by the client and
+   server respectively.  If a single "C:" or "S:" label applies to
+   multiple lines, then the line breaks between those lines are for
+   editorial clarity only and are not part of the actual protocol
+   exchange.  The five characters [...] means that something has been
+   elided.
+
+   Understanding of the IMAP message sequence numbers and UIDs and the
+   EXPUNGE response [RFC3501] is essential when reading this document.
+
+3.  IMAP Protocol Changes
+
+3.1.  QRESYNC Parameter to SELECT/EXAMINE
+
+   The Quick Resynchronization parameter to SELECT/EXAMINE commands has
+   four arguments:
+
+   o  the last known UIDVALIDITY,
+
+   o  the last known modification sequence,
+
+   o  the optional set of known UIDs, and
+
+   o  an optional parenthesized list of known sequence ranges and their
+      corresponding UIDs.
+
+   A server MUST respond with a tagged BAD response if the Quick
+   Resynchronization parameter to SELECT/EXAMINE command is specified
+   and the client hasn't issued "ENABLE QRESYNC" in the current
+   connection.
+
+
+
+
+Melnikov, et al.            Standards Track                     [Page 4]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   Before opening the specified mailbox, the server verifies all
+   arguments for syntactic validity.  If any parameter is not
+   syntactically valid, the server returns the tagged BAD response, and
+   the mailbox remains unselected.  Once the check is done, the server
+   opens the mailbox as if no SELECT/EXAMINE parameters are specified
+   (this is subject to processing of other parameters as defined in
+   other extensions).  In particular this means that the server MUST
+   send all untagged responses as specified in Sections 6.3.1 and 6.3.2
+   of [RFC3501].
+
+   After that, the server checks the UIDVALIDITY value provided by the
+   client.  If the provided UIDVALIDITY doesn't match the UIDVALIDITY
+   for the mailbox being opened, then the server MUST ignore the
+   remaining parameters and behave as if no dynamic message data
+   changed.  The client can discover this situation by comparing the
+   UIDVALIDITY value returned by the server.  This behavior allows the
+   client not to synchronize the mailbox or decide on the best
+   synchronization strategy.
+
+   Example: Attempting to resynchronize INBOX, but the provided
+            UIDVALIDITY parameter doesn't match the current UIDVALIDITY
+            value.
+
+   C: A02 SELECT INBOX (QRESYNC (67890007 20050715194045000
+            41,43:211,214:541))
+            S: * 464 EXISTS
+            S: * 3 RECENT
+            S: * OK [UIDVALIDITY 3857529045] UIDVALIDITY
+            S: * OK [UIDNEXT 550] Predicted next UID
+            S: * OK [HIGHESTMODSEQ 90060128194045007]
+            S: * OK [UNSEEN 12] Message 12 is first unseen
+            S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
+            S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
+            \Deleted \Seen \*)] Permanent flags
+            S: A02 OK [READ-WRITE] Sorry, UIDVALIDITY mismatch
+
+   Modification Sequence and UID Parameters:
+
+   A server that doesn't support the persistent storage of mod-sequences
+   for the mailbox MUST send the OK untagged response including the
+   NOMODSEQ response code with every successful SELECT or EXAMINE
+   command, as described in [CONDSTORE].  Such a server doesn't need to
+   remember mod-sequences for expunged messages in the mailbox.  It MUST
+   ignore the remaining parameters and behave as if no dynamic message
+   data changed.
+
+   If the provided UIDVALIDITY matches that of the selected mailbox, the
+   server then checks the last known modification sequence.
+
+
+
+Melnikov, et al.            Standards Track                     [Page 5]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   The server sends the client any pending flag changes (using FETCH
+   responses that MUST contain UIDs) and expunges those that have
+   occurred in this mailbox since the provided modification sequence.
+
+   If the list of known UIDs was also provided, the server should only
+   report flag changes and expunges for the specified messages.  If the
+   client did not provide the list of UIDs, the server acts as if the
+   client has specified "1:<maxuid>", where <maxuid> is the mailbox's
+   UIDNEXT value minus 1.  If the mailbox is empty and never had any
+   messages in it, then lack of the list of UIDs is interpreted as an
+   empty set of UIDs.
+
+   Thus, the client can process just these pending events and need not
+   perform a full resynchronization.  Without the message sequence
+   number matching information, the result of this step is semantically
+   equivalent to the client issuing:
+   tag1 UID FETCH "known-uids" (FLAGS) (CHANGEDSINCE
+   "mod-sequence-value" VANISHED)
+
+   Example:
+      C: A03 SELECT INBOX (QRESYNC (67890007
+         90060115194045000 41,43:211,214:541))
+      S: * OK [CLOSED]
+      S: * 314 EXISTS
+      S: * 15 RECENT
+      S: * OK [UIDVALIDITY 67890007] UIDVALIDITY
+      S: * OK [UIDNEXT 567] Predicted next UID
+      S: * OK [HIGHESTMODSEQ 90060115205545359]
+      S: * OK [UNSEEN 7] There are some unseen messages in the mailbox
+      S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
+      S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
+         \Deleted \Seen \*)] Permanent flags
+      S: * VANISHED (EARLIER) 41,43:116,118,120:211,214:540
+      S: * 49 FETCH (UID 117 FLAGS (\Seen \Answered) MODSEQ
+         (90060115194045001))
+      S: * 50 FETCH (UID 119 FLAGS (\Draft $MDNSent) MODSEQ
+         (90060115194045308))
+      S: ...
+      S: * 100 FETCH (UID 541 FLAGS (\Seen $Forwarded) MODSEQ
+         (90060115194045001))
+      S: A03 OK [READ-WRITE] mailbox selected
+
+   Message sequence match data:
+
+   A client MAY provide a parenthesized list of a message sequence set
+   and the corresponding UID sets.  Both MUST be provided in ascending
+   order.  The server uses this data to restrict the range for which it
+   provides expunged message information.
+
+
+
+Melnikov, et al.            Standards Track                     [Page 6]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   Conceptually, the client provides a small sample of sequence numbers
+   for which it knows the corresponding UIDs.  The server then compares
+   each sequence number and UID pair the client provides with the
+   current state of the mailbox.  If a pair matches, then the client
+   knows of any expunges up to, and including, the message, and thus
+   will not include that range in the VANISHED response, even if the
+   "mod-sequence-value" provided by the client is too old for the server
+   to have data of when those messages were expunged.
+
+   Thus, if the Nth message number in the first set in the list is 4,
+   and the Nth UID in the second set in the list is 8, and the mailbox's
+   fourth message has UID 8, then no UIDs equal to or less than 8 are
+   present in the VANISHED response.  If the (N+1)th message number is
+   12, and the (N+1)th UID is 24, and the (N+1)th message in the mailbox
+   has UID 25, then the lowest UID included in the VANISHED response
+   would be 9.
+
+   In the following two examples, the server is unable to remember
+   expunges at all, and only UIDs with messages divisible by three are
+   present in the mailbox.  In the first example, the client does not
+   use the fourth parameter; in the second, it provides it.  This
+   example is somewhat extreme, but shows that judicious usage of the
+   sequence match data can save a substantial amount of bandwidth.
+
+   Example:
+      C: A04 SELECT INBOX (QRESYNC (67890007
+         90060115194045000 1:29997))
+      S: * 10003 EXISTS
+      S: * 5 RECENT
+      S: * OK [UIDVALIDITY 67890007] UIDVALIDITY
+      S: * OK [UIDNEXT 30013] Predicted next UID
+      S: * OK [HIGHESTMODSEQ 90060115205545359]
+      S: * OK [UNSEEN 7] There are some unseen messages in the mailbox
+      S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
+      S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
+         \Deleted \Seen \*)] Permanent flags
+      S: * VANISHED (EARLIER) 1:2,4:5,7:8,10:11,13:14 [...]
+         29998:29999,30001:30002,30004:30005,30007:30008
+      S: * 9889 FETCH (UID 29667 FLAGS (\Seen \Answered) MODSEQ
+         (90060115194045027))
+      S: * 9890 FETCH (UID 29670 FLAGS (\Draft $MDNSent) MODSEQ
+         (90060115194045028))
+      S: ...
+      S: * 9999 FETCH (UID 29997 FLAGS (\Seen $Forwarded) MODSEQ
+         (90060115194045031))
+      S: A04 OK [READ-WRITE] mailbox selected
+
+
+
+
+
+Melnikov, et al.            Standards Track                     [Page 7]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   Example:
+      C: B04 SELECT INBOX (QRESYNC (67890007
+         90060115194045000 1:29997 (5000,7500,9000,9990:9999 15000,
+         22500,27000,29970,29973,29976,29979,29982,29985,29988,29991,
+         29994,29997)))
+      S: * 10003 EXISTS
+      S: * 5 RECENT
+      S: * OK [UIDVALIDITY 67890007] UIDVALIDITY
+      S: * OK [UIDNEXT 30013] Predicted next UID
+      S: * OK [HIGHESTMODSEQ 90060115205545359]
+      S: * OK [UNSEEN 7] There are some unseen messages in the mailbox
+      S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
+      S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
+         \Deleted \Seen \*)] Permanent flags
+      S: * VANISHED (EARLIER) 29998:29999,30001:30002,30004:30005,30007:
+         30008
+      S: * 9889 FETCH (UID 29667 FLAGS (\Seen \Answered) MODSEQ
+         (90060115194045027))
+      S: * 9890 FETCH (UID 29670 FLAGS (\Draft $MDNSent) MODSEQ
+         (90060115194045028))
+      S: ...
+      S: * 9999 FETCH (UID 29997 FLAGS (\Seen $Forwarded) MODSEQ
+         (90060115194045031))
+      S: B04 OK [READ-WRITE] mailbox selected
+
+3.2.  VANISHED UID FETCH Modifier
+
+   [IMAPABNF] has extended the syntax of the FETCH and UID FETCH
+   commands to include an optional FETCH modifier.  This document
+   defines a new UID FETCH modifier: VANISHED.
+
+   Note, that the VANISHED UID FETCH modifier is NOT allowed with a
+   FETCH command.  The server MUST return a tagged BAD response if this
+   response is specified as a modifier to the FETCH command.
+
+   A server MUST respond with a tagged BAD response if the VANISHED UID
+   FETCH modifier is specified and the client hasn't issued "ENABLE
+   QRESYNC" in the current connection.
+
+   The VANISHED UID FETCH modifier MUST only be specified together with
+   the CHANGEDSINCE UID FETCH modifier.
+
+   The VANISHED UID FETCH modifier instructs the server to report those
+   messages from the UID set parameter that have been expunged and whose
+   associated mod-sequence is larger than the specified mod-sequence.
+   That is, the client requests to be informed of messages from the
+   specified set that were expunged since the specified mod-sequence.
+   Note that the mod-sequence(s) associated with these messages were
+
+
+
+Melnikov, et al.            Standards Track                     [Page 8]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   updated when the messages were expunged (as described above).  The
+   expunged messages are reported using the VANISHED response as
+   described in Section 3.6, which MUST contain the EARLIER tag.  Any
+   VANISHED (EARLIER) responses MUST be returned before any FETCH
+   responses, as otherwise the client might get confused about how
+   message numbers map to UIDs.
+
+   Note: A server that receives a mod-sequence smaller than <minmodseq>,
+   where <minmodseq> is the value of the smallest expunged mod-sequence
+   it remembers minus one, MUST behave as if it was requested to report
+   all expunged messages from the provided UID set parameter.
+
+   Example 1: Without the VANISHED UID FETCH modifier, a CONDSTORE-aware
+   client [CONDSTORE] needs to issue separate commands to learn of flag
+   changes and expunged messages since the last synchronization:
+
+   C: s100 UID FETCH 300:500 (FLAGS) (CHANGEDSINCE 12345)
+   S: * 1 FETCH (UID 404 MODSEQ (65402) FLAGS (\Seen))
+   S: * 2 FETCH (UID 406 MODSEQ (75403) FLAGS (\Deleted))
+   S: * 4 FETCH (UID 408 MODSEQ (29738) FLAGS ($NoJunk
+       $AutoJunk $MDNSent))
+   S: s100 OK FETCH completed
+   C: s101 UID SEARCH 300:500
+   S: * SEARCH 404 406 407 408 410 412
+   S: s101 OK search completed
+
+   Where 300 and 500 are the lowest and highest UIDs from client's
+   cache.  The second SEARCH response tells the client that the messages
+   with UIDs 407, 410, and 412 are still present, but their flags
+   haven't changed since the specified modification sequence.
+
+   Using the VANISHED UID FETCH modifier, it is sufficient to issue only
+   a single command:
+
+   C: s100 UID FETCH 300:500 (FLAGS) (CHANGEDSINCE 12345
+       VANISHED)
+   S: * VANISHED (EARLIER) 300:310,405,411
+   S: * 1 FETCH (UID 404 MODSEQ (65402) FLAGS (\Seen))
+   S: * 2 FETCH (UID 406 MODSEQ (75403) FLAGS (\Deleted))
+   S: * 4 FETCH (UID 408 MODSEQ (29738) FLAGS ($NoJunk
+       $AutoJunk $MDNSent))
+   S: s100 OK FETCH completed
+
+
+
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                     [Page 9]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+3.3.  EXPUNGE Command
+
+   Arguments: none
+
+   Responses: untagged responses: EXPUNGE or VANISHED
+
+   Result: OK - expunge completed
+           NO - expunge failure: can't expunge (e.g., permission denied)
+           BAD - command unknown or arguments invalid
+
+   This section updates the definition of the EXPUNGE command described
+   in Section 6.4.3 of [RFC3501].
+
+   The EXPUNGE command permanently removes all messages that have the
+   \Deleted flag set from the currently selected mailbox.  Before
+   returning an OK to the client, those messages that are removed are
+   reported using a VANISHED response or EXPUNGE responses.
+
+   If the server is capable of storing modification sequences for the
+   selected mailbox, it MUST increment the per-mailbox mod-sequence if
+   at least one message was permanently removed due to the execution of
+   the EXPUNGE command.  For each permanently removed message, the
+   server MUST remember the incremented mod-sequence and corresponding
+   UID.  If at least one message got expunged, the server MUST send the
+   updated per-mailbox modification sequence using the HIGHESTMODSEQ
+   response code (defined in [CONDSTORE]) in the tagged OK response.
+
+      Example:    C: A202 EXPUNGE
+                  S: * 3 EXPUNGE
+                  S: * 3 EXPUNGE
+                  S: * 5 EXPUNGE
+                  S: * 8 EXPUNGE
+                  S: A202 OK [HIGHESTMODSEQ 20010715194045319] expunged
+
+   Note: In this example, messages 3, 4, 7, and 11 had the \Deleted flag
+   set.  The first "* 3 EXPUNGE" reports message # 3 as expunged.  The
+   second "* 3 EXPUNGE" reports message # 4 as expunged (the message
+   number got decremented due to the previous EXPUNGE response).  See
+   the description of the EXPUNGE response in [RFC3501] for further
+   explanation.
+
+   Note that if the server chooses to always send VANISHED responses
+   instead of EXPUNGE responses, the previous example might look like
+   this:
+
+      Example:    C: B202 EXPUNGE
+                  S: * VANISHED 405,407,410,425
+                  S: B202 OK [HIGHESTMODSEQ 20010715194045319] expunged
+
+
+
+Melnikov, et al.            Standards Track                    [Page 10]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   Here messages with message numbers 3, 4, 7, and 11 have respective
+   UIDs 405, 407, 410, and 425.
+
+3.4.  CLOSE Command
+
+   Arguments: none
+
+   Responses: no specific responses for this command
+
+   Result: OK - close completed, now in authenticated state
+           BAD - command unknown or arguments invalid
+
+   This section updates the definition of the CLOSE command described in
+   Section 6.4.2 of [RFC3501].
+
+   The CLOSE command permanently removes all messages that have the
+   \Deleted flag set from the currently selected mailbox, and returns to
+   the authenticated state from the selected state.  No untagged EXPUNGE
+   (or VANISHED) responses are sent.
+
+   If the server is capable of storing modification sequences for the
+   selected mailbox, it MUST increment the per-mailbox mod-sequence if
+   at least one message was permanently removed due to the execution of
+   the CLOSE command.  For each permanently removed message, the server
+   MUST remember the incremented mod-sequence and corresponding UID.  If
+   at least one message got expunged, the server MUST send the updated
+   per-mailbox modification sequence using the HIGHESTMODSEQ response
+   code (defined in [CONDSTORE]) in the tagged OK response.
+
+      Example:    C: A202 CLOSE
+                  S: A202 OK [HIGHESTMODSEQ 20010715194045319] done
+
+3.5.  UID EXPUNGE Command
+
+   Arguments: message set
+
+   Responses: untagged responses: EXPUNGE or VANISHED
+
+   Result: OK - expunge completed
+           NO - expunge failure: can't expunge (e.g., permission denied)
+           BAD - command unknown or arguments invalid
+
+   This section updates the definition of the UID EXPUNGE command
+   described in Section 2.1 of [UIDPLUS].  Servers that implement both
+   [UIDPLUS] and QRESYNC extensions must implement UID EXPUNGE as
+   described in this section.
+
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 11]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   The UID EXPUNGE command permanently removes from the currently
+   selected mailbox all messages that both have the \Deleted flag set
+   and have a UID that is included in the specified message set.  If a
+   message either does not have the \Deleted flag set or has a UID that
+   is not included in the specified message set, it is not affected.
+
+   This command is particularly useful for disconnected mode clients.
+   By using UID EXPUNGE instead of EXPUNGE when resynchronizing with the
+   server, the client can avoid inadvertently removing any messages that
+   have been marked as \Deleted by other clients between the time that
+   the client was last connected and the time the client resynchronizes.
+
+   Before returning an OK to the client, those messages that are removed
+   are reported using a VANISHED response or EXPUNGE responses.
+
+   If the server is capable of storing modification sequences for the
+   selected mailbox, it MUST increment the per-mailbox mod-sequence if
+   at least one message was permanently removed due to the execution of
+   the UID EXPUNGE command.  For each permanently removed message, the
+   server MUST remember the incremented mod-sequence and corresponding
+   UID.  If at least one message got expunged, the server MUST send the
+   updated per-mailbox modification sequence using the HIGHESTMODSEQ
+   response code (defined in [CONDSTORE]) in the tagged OK response.
+
+   Example:    C: . UID EXPUNGE 3000:3002
+               S: * 3 EXPUNGE
+               S: * 3 EXPUNGE
+               S: * 3 EXPUNGE
+               S: . OK [HIGHESTMODSEQ 20010715194045319] Ok
+
+   Note: In this example, at least messages with message numbers 3, 4,
+   and 5 (UIDs 3000 to 3002) had the \Deleted flag set.  The first "* 3
+   EXPUNGE" reports message # 3 as expunged.  The second "* 3 EXPUNGE"
+   reports message # 4 as expunged (the message number got decremented
+   due to the previous EXPUNGE response).  See the description of the
+   EXPUNGE response in [RFC3501] for further explanation.
+
+3.6.  VANISHED Response
+
+   Contents:  an optional EARLIER tag
+
+   list of UIDs
+
+   The VANISHED response reports that the specified UIDs have been
+   permanently removed from the mailbox.  This response is similar to
+   the EXPUNGE response [RFC3501]; however, it can return information
+   about multiple messages, and it returns UIDs instead of message
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 12]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   numbers.  The first benefit saves bandwidth, while the second is more
+   convenient for clients that only use UIDs to access the IMAP server.
+
+   The VANISHED response has the same restrictions on when it can be
+   sent as does the EXPUNGE response (see below).
+
+   The VANISHED response has two forms.  The first form contains the
+   EARLIER tag, which signifies that the response was caused by a UID
+   FETCH (VANISHED) or a SELECT/EXAMINE (QRESYNC) command.  This
+   response is sent if the UID set parameter to the UID FETCH (VANISHED)
+   command includes UIDs of messages that are no longer in the mailbox.
+   When the client sees a VANISHED EARLIER response, it MUST NOT
+   decrement message sequence numbers for each successive message in the
+   mailbox.
+
+   The second form doesn't contain the EARLIER tag and is described
+   below.  Once a client has issued "ENABLE QRESYNC", the server SHOULD
+   use the VANISHED response without the EARLIER tag instead of the
+   EXPUNGE response.  The server SHOULD continue using VANISHED in lieu
+   of EXPUNGE for the duration of the connection.  In particular, this
+   affects the EXPUNGE [RFC3501] and UID EXPUNGE [UIDPLUS] commands, as
+   well as messages expunged in other connections.  Such a VANISHED
+   response MUST NOT contain the EARLIER tag.
+
+   A VANISHED response sent because of an EXPUNGE or UID EXPUNGE command
+   or because messages were expunged in other connections (i.e., the
+   VANISHED response without the EARLIER tag) also decrements the number
+   of messages in the mailbox; it is not necessary for the server to
+   send an EXISTS response with the new value.  It also decrements
+   message sequence numbers for each successive message in the mailbox
+   (see the example at the end of this section).  Note that a VANISHED
+   response caused by EXPUNGE, UID EXPUNGE, or messages expunged in
+   other connections SHOULD only contain UIDs for messages expunged
+   since the last VANISHED/EXPUNGE response sent for the currently
+   opened mailbox or since the mailbox was opened.  That is, servers
+   SHOULD NOT send UIDs for previously expunged messages, unless
+   explicitly requested to do so by the UID FETCH (VANISHED) command.
+
+   Note that client implementors must take care to properly decrement
+   the number of messages in the mailbox even if a server violates this
+   last SHOULD or repeats the same UID multiple times in the returned
+   UID set.  In general, this means that a client using this extension
+   should either avoid using message numbers entirely, or have a
+   complete mapping of UIDs to message sequence numbers for the selected
+   mailbox.
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 13]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   Because clients handle the two different forms of the VANISHED
+   response differently, servers MUST NOT report UIDs resulting from a
+   UID FETCH (VANISHED) or a SELECT/EXAMINE (QRESYNC) in the same
+   VANISHED response as UIDs of messages expunged now (i.e., messages
+   expunged in other connections).  Instead, the server MUST send
+   separate VANISHED responses: one with the EARLIER tag and one
+   without.
+
+   A VANISHED response MUST NOT be sent when no command is in progress,
+   nor while responding to a FETCH, STORE, or SEARCH command.  This rule
+   is necessary to prevent a loss of synchronization of message sequence
+   numbers between client and server.  A command is not "in progress"
+   until the complete command has been received; in particular, a
+   command is not "in progress" during the negotiation of command
+   continuation.
+
+   Note: UID FETCH, UID STORE, and UID SEARCH are different commands
+   from FETCH, STORE, and SEARCH.  A VANISHED response MAY be sent
+   during a UID command.  However, the VANISHED response MUST NOT be
+   sent during a UID SEARCH command that contains message numbers in the
+   search criteria.
+
+   The update from the VANISHED response MUST be recorded by the client.
+
+   Example: Let's assume that there is the following mapping between
+   message numbers and UIDs in the currently selected mailbox (here "X"
+   marks messages with the \Deleted flag set, and "x" represents UIDs
+   which are not relevant for the example):
+
+   Message numbers:   1    2    3    4    5  6   7  8  9 10  11
+   UIDs:              x  504  505  507  508  x 510  x  x  x 625
+   \Deleted messages:           X    X           X            X
+
+   In the presence of the extension defined in this document:
+
+   C: A202 EXPUNGE
+   S: * VANISHED 505,507,510,625
+   S: A202 OK EXPUNGE completed
+
+   Without the QRESYNC extension, the same example might look like:
+
+   C: A202 EXPUNGE
+   S: * 3 EXPUNGE
+   S: * 3 EXPUNGE
+   S: * 5 EXPUNGE
+   S: * 8 EXPUNGE
+   S: A202 OK EXPUNGE completed
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 14]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   (Continuing previous example) If subsequently messages with UIDs 504
+   and 508 got marked as \Deleted:
+
+   C: A210 EXPUNGE
+   S: * VANISHED 504,508
+   S: A210 OK EXPUNGE completed
+
+   i.e., the last VANISHED response only contains UIDs of messages
+   expunged since the previous VANISHED response.
+
+3.7.  CLOSED Response Code
+
+   The CLOSED response code has no parameters.  A server implementing
+   the extension defined in this document MUST return the CLOSED
+   response code when the currently selected mailbox is closed
+   implicitly using the SELECT/EXAMINE command on another mailbox.  The
+   CLOSED response code serves as a boundary between responses for the
+   previously opened mailbox (which was closed) and the newly selected
+   mailbox: all responses before the CLOSED response code relate to the
+   mailbox that was closed, and all subsequent responses relate to the
+   newly opened mailbox.
+
+   There is no need to return the CLOSED response code on completion of
+   the CLOSE or the UNSELECT [UNSELECT] command (or similar) whose
+   purpose is to close the currently selected mailbox without opening a
+   new one.
+
+4.  Server Implementation Considerations
+
+   This section describes a minimalist implementation, a moderate
+   implementation, and an example of a full implementation.
+
+4.1.  Server Implementations That Don't Store Extra State
+
+   Strictly speaking, a server implementation that doesn't remember mod-
+   sequences associated with expunged messages can be considered
+   compliant with this specification.  Such implementations return all
+   expunged messages specified in the UID set of the UID FETCH
+   (VANISHED) command every time, without paying attention to the
+   specified CHANGEDSINCE mod-sequence.  Such implementations are
+   discouraged, as they can end up returning VANISHED responses that are
+   bigger than the result of a UID SEARCH command for the same UID set.
+
+   Clients that use the message sequence match data can reduce the scope
+   of this VANISHED response substantially in the typical case where
+   expunges have not happened, or happen only toward the end of the
+   mailbox.
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 15]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+4.2.  Server Implementations Storing Minimal State
+
+   A server that stores the HIGHESTMODSEQ value at the time of the last
+   EXPUNGE can omit the VANISHED response when a client provides a
+   MODSEQ value that is equal to, or higher than, the current value of
+   this datum, that is, when there have been no EXPUNGEs.
+
+   A client providing message sequence match data can reduce the scope
+   as above.  In the case where there have been no expunges, the server
+   can ignore this data.
+
+4.3.  Additional State Required on the Server
+
+   When compared to the [CONDSTORE] extension, this extension requires
+   servers to store additional state associated with expunged messages.
+   Note that implementations are not required to store this state in
+   persistent storage; however, use of persistent storage is advisable.
+
+   One possible way to correctly implement the extension described in
+   this document is to store a queue of <UID set, mod-sequence> pairs.
+   <UID set> can be represented as a sequence of <min UID, max UID>
+   pairs.
+
+   When messages are expunged, one or more entries are added to the
+   queue tail.
+
+   When the server receives a request to return messages expunged since
+   a given mod-sequence, it will search the queue from the tail (i.e.,
+   going from the highest expunged mod-sequence to the lowest) until it
+   sees the first record with a mod-sequence less than or equal to the
+   given mod-sequence or it reaches the head of the queue.
+
+   Note that indefinitely storing information about expunged messages
+   can cause storage and related problems for an implementation.  In the
+   worst case, this could result in almost 64Gb of storage for each IMAP
+   mailbox.  For example, consider an implementation that stores <min
+   UID, max UID, mod-sequence> triples for each range of messages
+   expunged at the same time.  Each triple requires 16 octets: 4 octets
+   for each of the two UIDs, and 8 octets for the mod-sequence.  Assume
+   that there is a mailbox containing a single message with a UID of
+   2**32-1 (the maximum possible UID value), where messages had
+   previously existed with UIDs starting at 1, and have been expunged
+   one at a time.  For this mailbox alone, storage is required for the
+   triples <1, 1, modseq1>, <2, 2, modseq2>, ..., <2**32-2, 2**32-2,
+   modseq4294967294>.
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 16]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   Hence, implementations are encouraged to adopt strategies to protect
+   against such storage problems, such as limiting the size of the queue
+   used to store mod-sequences for expunged messages and "expiring"
+   older records when this limit is reached.  When the selected
+   implementation-specific queue limit is reached, the oldest record(s)
+   are deleted from the queue (note that such records are located at the
+   queue head).  For all such "expired" records, the server needs to
+   store a single mod-sequence, which is the highest mod-sequence for
+   all "expired" expunged messages.
+
+   Note that if the client provides the message sequence match data,
+   this can heavily reduce the data cost of sending a complete set of
+   missing UIDs; thus, reducing the problems for clients if a server is
+   unable to persist much of this queue.  If the queue contains data
+   back to the requested mod-sequence, this data can be ignored.
+
+   Also, note that if the UIDVALIDITY of the mailbox changes or if the
+   mailbox is deleted, then any state associated with expunged messages
+   doesn't need to be preserved and SHOULD be deleted.
+
+5.  Updated Synchronization Sequence
+
+   This section updates the description of optimized synchronization in
+   Section 6.1 of the [IMAP-DISC].
+
+   An advanced disconnected mail client should use the QRESYNC and
+   [CONDSTORE] extensions when they are supported by the server.  The
+   client uses the value from the HIGHESTMODSEQ OK response code
+   received on mailbox opening to determine if it needs to
+   resynchronize.  Once the synchronization is complete, it MUST cache
+   the received value (unless the mailbox UIDVALIDITY value has changed;
+   see below).  The client MUST update its copy of the HIGHESTMODSEQ
+   value whenever the server sends a subsequent HIGHESTMODSEQ OK
+   response code.
+
+   After completing a full synchronization, the client MUST also take
+   note of any unsolicited MODSEQ FETCH data items received from the
+   server.  Whenever the client receives a tagged response to a command,
+   it calculates the highest value among all MODSEQ FETCH data items
+   received since the last tagged response.  If this value is bigger
+   than the client's copy of the HIGHESTMODSEQ value, then the client
+   MUST use this value as its new HIGHESTMODSEQ value.
+
+   Note: It is not safe to update the client's copy of the HIGHESTMODSEQ
+   value with a MODSEQ FETCH data item value as soon as it is received
+   because servers are not required to send MODSEQ FETCH data items in
+   increasing modseqence order.  This can lead to the client missing
+   some changes in case of connectivity loss.
+
+
+
+Melnikov, et al.            Standards Track                    [Page 17]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   When opening the mailbox for synchronization, the client uses the
+   QRESYNC parameter to the SELECT/EXAMINE command.  The QRESYNC
+   parameter is followed by the UIDVALIDITY and mailbox HIGHESTMODSEQ
+   values, as known to the client.  It can be optionally followed by the
+   set of UIDs, for example, if the client is only interested in partial
+   synchronization of the mailbox.  The client may also transmit a list
+   containing its knowledge of message numbers.
+
+   If the SELECT/EXAMINE command is successful, the client compares
+   UIDVALIDITY as described in step d)1) in Section 3 of the
+   [IMAP-DISC].  If the cached UIDVALIDITY value matches the one
+   returned by the server and the server also returns the HIGHESTMODSEQ
+   response code, then the server reports expunged messages and returns
+   flag changes for all messages specified by the client in the UID set
+   parameter (or for all messages in the mailbox, if the client omitted
+   the UID set parameter).  At this point, the client is synchronized,
+   except for maybe the new messages.
+
+   If upon a successful SELECT/EXAMINE (QRESYNC) command the client
+   receives a NOMODSEQ OK untagged response (instead of the
+   HIGHESTMODSEQ response code), it MUST remove the last known
+   HIGHESTMODSEQ value from its cache and follow the more general
+   instructions in Section 3 of the [IMAP-DISC].
+
+   At this point, the client is in sync with the server regarding old
+   messages.  This client can now fetch information about new messages
+   (if requested by the user).
+
+   Step d) ("Server-to-client synchronization") in Section 4 of the
+   [IMAP-DISC] in the presence of the QRESYNC & CONDSTORE extensions is
+   amended as follows:
+
+   d) "Server-to-client synchronization" -- for each mailbox that
+      requires synchronization, do the following:
+
+   1a) Check the mailbox UIDVALIDITY (see Section 4.1 of the [IMAP-DISC]
+       for more details) after issuing SELECT/EXAMINE (QRESYNC) command.
+
+       If the UIDVALIDITY value returned by the server differs, the
+       client MUST
+
+       *   empty the local cache of that mailbox;
+
+       *   "forget" the cached HIGHESTMODSEQ value for the mailbox;
+
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 18]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+       *   remove any pending "actions" which refer to UIDs in that
+           mailbox.  Note, this doesn't affect actions performed on
+           client generated fake UIDs (see Section 5 of the
+           [IMAP-DISC]);
+
+   2)  Fetch the current "descriptors";
+
+       I) Discover new messages.
+
+   3)  Fetch the bodies of any "interesting" messages that the client
+       doesn't already have.
+
+   Example: The UIDVALIDITY value is the same, but the HIGHESTMODSEQ
+            value has changed on the server while the client was
+            offline:
+
+    C: A142 SELECT INBOX (QRESYNC (3857529045 20010715194032001 1:198))
+    S: * 172 EXISTS
+    S: * 1 RECENT
+    S: * OK [UNSEEN 12] Message 12 is first unseen
+    S: * OK [UIDVALIDITY 3857529045] UIDs valid
+    S: * OK [UIDNEXT 201] Predicted next UID
+    S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+    S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+    S: * OK [HIGHESTMODSEQ 20010715194045007]
+    S: * VANISHED (EARLIER) 1:5,7:8,10:15
+    S: * 2 FETCH (UID 6 MODSEQ (20010715205008000)
+        FLAGS (\Deleted))
+    S: * 5 FETCH (UID 9 MODSEQ (20010715195517000)
+        FLAGS ($NoJunk $AutoJunk $MDNSent))
+       ...
+    S: A142 OK [READ-WRITE] SELECT completed
+
+6.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].
+
+   Non-terminals referenced but not defined below are as defined by
+   [RFC3501], [CONDSTORE], or [IMAPABNF].
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper or lower case characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 19]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+   capability          =/ "QRESYNC"
+
+   select-param        =  "QRESYNC" SP "(" uidvalidity SP
+                       mod-sequence-value [SP known-uids]
+                       [SP seq-match-data] ")"
+                       ;; conforms to the generic select-param
+                       ;; syntax defined in [IMAPABNF]
+
+   seq-match-data      =  "(" known-sequence-set SP known-uid-set ")"
+
+   uidvalidity         =  nz-number
+
+   known-uids          =  sequence-set
+                       ;; sequence of UIDs, "*" is not allowed
+
+   known-sequence-set  =  sequence-set
+                       ;; set of message numbers corresponding to
+                       ;; the UIDs in known-uid-set, in ascending order.
+                       ;; * is not allowed.
+
+   known-uid-set       =  sequence-set
+                       ;; set of UIDs corresponding to the messages in
+                       ;; known-sequence-set, in ascending order.
+                       ;; * is not allowed.
+
+   message-data        =/ expunged-resp
+
+   expunged-resp       =  "VANISHED" [SP "(EARLIER)"] SP known-uids
+
+   rexpunges-fetch-mod =  "VANISHED"
+                       ;; VANISHED UID FETCH modifier conforms
+                       ;; to the fetch-modifier syntax
+                       ;; defined in [IMAPABNF].  It is only
+                       ;; allowed in the UID FETCH command.
+
+   resp-text-code      =/ "CLOSED"
+
+7.  Security Considerations
+
+   As always, it is important to thoroughly test clients and servers
+   implementing this extension, as it changes how the server reports
+   expunged messages to the client.
+
+   Security considerations relevant to [CONDSTORE] are relevant to this
+   extension.
+
+   This document doesn't raise any new security concerns not already
+   raised by [CONDSTORE] or [RFC3501].
+
+
+
+Melnikov, et al.            Standards Track                    [Page 20]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+8.  IANA Considerations
+
+   IMAP4 capabilities are registered by publishing a standards track or
+   IESG approved experimental RFC.  The registry is currently located
+   at:
+
+      http://www.iana.org/assignments/imap4-capabilities
+
+   This document defines the QRESYNC IMAP capability.  IANA has added
+   this capability to the registry.
+
+9.  Acknowledgments
+
+   Thanks to Steve Hole, Cyrus Daboo, and Michael Wener for encouraging
+   creation of this document.
+
+   Valuable comments, both in agreement and in dissent, were received
+   from Timo Sirainen, Michael Wener, Randall Gellens, Arnt Gulbrandsen,
+   Chris Newman, Peter Coates, Mark Crispin, Elwyn Davies, Dan Karp,
+   Eric Rescorla, and Mike Zraly.
+
+   This document takes substantial text from [RFC3501] by Mark Crispin.
+
+10.  References
+
+10.1.  Normative References
+
+   [ABNF]       Crocker, D. and P. Overell, "Augmented BNF for Syntax
+                Specifications: ABNF", STD 68, RFC 5234, January 2008.
+
+   [CONDSTORE]  Melnikov, A. and S. Hole, "IMAP Extension for
+                Conditional STORE Operation or Quick Flag Changes
+                Resynchronization", RFC 4551, June 2006.
+
+   [ENABLE]     Gulbrandsen, A., Ed. and A. Melnikov, Ed., "The IMAP
+                ENABLE Extension", RFC 5161, March 2008.
+
+   [IMAPABNF]   Melnikov, A. and C. Daboo, "Collected Extensions to
+                IMAP4 ABNF", RFC 4466, April 2006.
+
+   [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate
+                Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC3501]    Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+                4rev1", RFC 3501, March 2003.
+
+   [UIDPLUS]    Crispin, M., "Internet Message Access Protocol (IMAP) -
+                UIDPLUS extension", RFC 4315, December 2005.
+
+
+
+Melnikov, et al.            Standards Track                    [Page 21]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+10.2.  Informative References
+
+   [IMAP-DISC]  Melnikov, A., Ed., "Synchronization Operations For
+                Disconnected Imap4 Clients", RFC 4549, June 2006.
+
+   [UNSELECT]   Melnikov, A., "Internet Message Access Protocol (IMAP)
+                UNSELECT command", RFC 3691, February 2004.
+
+Authors' Addresses
+
+   Alexey Melnikov
+   Isode Ltd
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex  TW12 2BX
+   UK
+
+   EMail: Alexey.Melnikov@isode.com
+
+
+   Dave Cridland
+   Isode Ltd
+   5 Castle Business Village
+   36 Station Road
+   Hampton, Middlesex  TW12 2BX
+   UK
+
+   EMail: dave.cridland@isode.com
+
+
+   Corby Wilson
+   Nokia
+   5 Wayside Rd.
+   Burlington, MA  01803
+   USA
+
+   EMail: corby@computer.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 22]
+
+RFC 5162               IMAP Quick Mailbox Resync              March 2008
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2008).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov, et al.            Standards Track                    [Page 23]
+
diff --git a/imap/docs/rfc/rfc5234.txt b/imap/docs/rfc/rfc5234.txt
new file mode 100644
index 00000000..42bb44ca
--- /dev/null
+++ b/imap/docs/rfc/rfc5234.txt
@@ -0,0 +1,899 @@
+
+
+
+
+
+
+Network Working Group                                    D. Crocker, Ed.
+Request for Comments: 5234                   Brandenburg InternetWorking
+STD: 68                                                       P. Overell
+Obsoletes: 4234                                                THUS plc.
+Category: Standards Track                                   January 2008
+
+
+             Augmented BNF for Syntax Specifications: ABNF
+
+Status of This Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Abstract
+
+   Internet technical specifications often need to define a formal
+   syntax.  Over the years, a modified version of Backus-Naur Form
+   (BNF), called Augmented BNF (ABNF), has been popular among many
+   Internet specifications.  The current specification documents ABNF.
+   It balances compactness and simplicity with reasonable
+   representational power.  The differences between standard BNF and
+   ABNF involve naming rules, repetition, alternatives, order-
+   independence, and value ranges.  This specification also supplies
+   additional rule definitions and encoding for a core lexical analyzer
+   of the type common to several Internet specifications.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                     [Page 1]
+
+RFC 5234                          ABNF                      January 2008
+
+
+Table of Contents
+
+   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
+   2.  Rule Definition  . . . . . . . . . . . . . . . . . . . . . . .  3
+     2.1.  Rule Naming  . . . . . . . . . . . . . . . . . . . . . . .  3
+     2.2.  Rule Form  . . . . . . . . . . . . . . . . . . . . . . . .  4
+     2.3.  Terminal Values  . . . . . . . . . . . . . . . . . . . . .  4
+     2.4.  External Encodings . . . . . . . . . . . . . . . . . . . .  6
+   3.  Operators  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
+     3.1.  Concatenation:  Rule1 Rule2  . . . . . . . . . . . . . . .  6
+     3.2.  Alternatives:  Rule1 / Rule2 . . . . . . . . . . . . . . .  7
+     3.3.  Incremental Alternatives: Rule1 =/ Rule2 . . . . . . . . .  7
+     3.4.  Value Range Alternatives:  %c##-## . . . . . . . . . . . .  8
+     3.5.  Sequence Group:  (Rule1 Rule2) . . . . . . . . . . . . . .  8
+     3.6.  Variable Repetition:  *Rule  . . . . . . . . . . . . . . .  9
+     3.7.  Specific Repetition:  nRule  . . . . . . . . . . . . . . .  9
+     3.8.  Optional Sequence:  [RULE] . . . . . . . . . . . . . . . .  9
+     3.9.  Comment:  ; Comment  . . . . . . . . . . . . . . . . . . .  9
+     3.10. Operator Precedence  . . . . . . . . . . . . . . . . . . . 10
+   4.  ABNF Definition of ABNF  . . . . . . . . . . . . . . . . . . . 10
+   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
+   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
+     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
+     6.2.  Informative References . . . . . . . . . . . . . . . . . . 12
+   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 13
+   Appendix B.  Core ABNF of ABNF . . . . . . . . . . . . . . . . . . 13
+     B.1.  Core Rules . . . . . . . . . . . . . . . . . . . . . . . . 13
+     B.2.  Common Encoding  . . . . . . . . . . . . . . . . . . . . . 15
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                     [Page 2]
+
+RFC 5234                          ABNF                      January 2008
+
+
+1.  Introduction
+
+   Internet technical specifications often need to define a formal
+   syntax and are free to employ whatever notation their authors deem
+   useful.  Over the years, a modified version of Backus-Naur Form
+   (BNF), called Augmented BNF (ABNF), has been popular among many
+   Internet specifications.  It balances compactness and simplicity with
+   reasonable representational power.  In the early days of the Arpanet,
+   each specification contained its own definition of ABNF.  This
+   included the email specifications, [RFC733] and then [RFC822], which
+   came to be the common citations for defining ABNF.  The current
+   document separates those definitions to permit selective reference.
+   Predictably, it also provides some modifications and enhancements.
+
+   The differences between standard BNF and ABNF involve naming rules,
+   repetition, alternatives, order-independence, and value ranges.
+   Appendix B supplies rule definitions and encoding for a core lexical
+   analyzer of the type common to several Internet specifications.  It
+   is provided as a convenience and is otherwise separate from the meta
+   language defined in the body of this document, and separate from its
+   formal status.
+
+2.  Rule Definition
+
+2.1.  Rule Naming
+
+   The name of a rule is simply the name itself, that is, a sequence of
+   characters, beginning with an alphabetic character, and followed by a
+   combination of alphabetics, digits, and hyphens (dashes).
+
+   NOTE:
+
+      Rule names are case insensitive.
+
+   The names <rulename>, <Rulename>, <RULENAME>, and <rUlENamE> all
+   refer to the same rule.
+
+   Unlike original BNF, angle brackets ("<", ">") are not required.
+   However, angle brackets may be used around a rule name whenever their
+   presence facilitates in discerning the use of a rule name.  This is
+   typically restricted to rule name references in free-form prose, or
+   to distinguish partial rules that combine into a string not separated
+   by white space, such as shown in the discussion about repetition,
+   below.
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                     [Page 3]
+
+RFC 5234                          ABNF                      January 2008
+
+
+2.2.  Rule Form
+
+   A rule is defined by the following sequence:
+
+         name =  elements crlf
+
+   where <name> is the name of the rule, <elements> is one or more rule
+   names or terminal specifications, and <crlf> is the end-of-line
+   indicator (carriage return followed by line feed).  The equal sign
+   separates the name from the definition of the rule.  The elements
+   form a sequence of one or more rule names and/or value definitions,
+   combined according to the various operators defined in this document,
+   such as alternative and repetition.
+
+   For visual ease, rule definitions are left aligned.  When a rule
+   requires multiple lines, the continuation lines are indented.  The
+   left alignment and indentation are relative to the first lines of the
+   ABNF rules and need not match the left margin of the document.
+
+2.3.  Terminal Values
+
+   Rules resolve into a string of terminal values, sometimes called
+   characters.  In ABNF, a character is merely a non-negative integer.
+   In certain contexts, a specific mapping (encoding) of values into a
+   character set (such as ASCII) will be specified.
+
+   Terminals are specified by one or more numeric characters, with the
+   base interpretation of those characters indicated explicitly.  The
+   following bases are currently defined:
+
+         b           =  binary
+
+         d           =  decimal
+
+         x           =  hexadecimal
+
+   Hence:
+
+         CR          =  %d13
+
+         CR          =  %x0D
+
+   respectively specify the decimal and hexadecimal representation of
+   [US-ASCII] for carriage return.
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                     [Page 4]
+
+RFC 5234                          ABNF                      January 2008
+
+
+   A concatenated string of such values is specified compactly, using a
+   period (".") to indicate a separation of characters within that
+   value.  Hence:
+
+         CRLF        =  %d13.10
+
+   ABNF permits the specification of literal text strings directly,
+   enclosed in quotation marks.  Hence:
+
+         command     =  "command string"
+
+   Literal text strings are interpreted as a concatenated set of
+   printable characters.
+
+   NOTE:
+
+      ABNF strings are case insensitive and the character set for these
+      strings is US-ASCII.
+
+   Hence:
+
+         rulename = "abc"
+
+   and:
+
+         rulename = "aBc"
+
+   will match "abc", "Abc", "aBc", "abC", "ABc", "aBC", "AbC", and
+   "ABC".
+
+      To specify a rule that is case sensitive, specify the characters
+      individually.
+
+   For example:
+
+         rulename    =  %d97 %d98 %d99
+
+   or
+
+         rulename    =  %d97.98.99
+
+   will match only the string that comprises only the lowercase
+   characters, abc.
+
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                     [Page 5]
+
+RFC 5234                          ABNF                      January 2008
+
+
+2.4.  External Encodings
+
+   External representations of terminal value characters will vary
+   according to constraints in the storage or transmission environment.
+   Hence, the same ABNF-based grammar may have multiple external
+   encodings, such as one for a 7-bit US-ASCII environment, another for
+   a binary octet environment, and still a different one when 16-bit
+   Unicode is used.  Encoding details are beyond the scope of ABNF,
+   although Appendix B provides definitions for a 7-bit US-ASCII
+   environment as has been common to much of the Internet.
+
+   By separating external encoding from the syntax, it is intended that
+   alternate encoding environments can be used for the same syntax.
+
+3.  Operators
+
+3.1.  Concatenation:  Rule1 Rule2
+
+   A rule can define a simple, ordered string of values (i.e., a
+   concatenation of contiguous characters) by listing a sequence of rule
+   names.  For example:
+
+         foo         =  %x61           ; a
+
+         bar         =  %x62           ; b
+
+         mumble      =  foo bar foo
+
+   So that the rule <mumble> matches the lowercase string "aba".
+
+   Linear white space: Concatenation is at the core of the ABNF parsing
+   model.  A string of contiguous characters (values) is parsed
+   according to the rules defined in ABNF.  For Internet specifications,
+   there is some history of permitting linear white space (space and
+   horizontal tab) to be freely and implicitly interspersed around major
+   constructs, such as delimiting special characters or atomic strings.
+
+   NOTE:
+
+      This specification for ABNF does not provide for implicit
+      specification of linear white space.
+
+   Any grammar that wishes to permit linear white space around
+   delimiters or string segments must specify it explicitly.  It is
+   often useful to provide for such white space in "core" rules that are
+   then used variously among higher-level rules.  The "core" rules might
+   be formed into a lexical analyzer or simply be part of the main
+   ruleset.
+
+
+
+Crocker & Overell           Standards Track                     [Page 6]
+
+RFC 5234                          ABNF                      January 2008
+
+
+3.2.  Alternatives:  Rule1 / Rule2
+
+   Elements separated by a forward slash ("/") are alternatives.
+   Therefore,
+
+         foo / bar
+
+   will accept <foo> or <bar>.
+
+   NOTE:
+
+      A quoted string containing alphabetic characters is a special form
+      for specifying alternative characters and is interpreted as a non-
+      terminal representing the set of combinatorial strings with the
+      contained characters, in the specified order but with any mixture
+      of upper- and lowercase.
+
+3.3.  Incremental Alternatives: Rule1 =/ Rule2
+
+   It is sometimes convenient to specify a list of alternatives in
+   fragments.  That is, an initial rule may match one or more
+   alternatives, with later rule definitions adding to the set of
+   alternatives.  This is particularly useful for otherwise independent
+   specifications that derive from the same parent ruleset, such as
+   often occurs with parameter lists.  ABNF permits this incremental
+   definition through the construct:
+
+         oldrule     =/ additional-alternatives
+
+   So that the ruleset
+
+         ruleset     =  alt1 / alt2
+
+         ruleset     =/ alt3
+
+         ruleset     =/ alt4 / alt5
+
+   is the same as specifying
+
+         ruleset     =  alt1 / alt2 / alt3 / alt4 / alt5
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                     [Page 7]
+
+RFC 5234                          ABNF                      January 2008
+
+
+3.4.  Value Range Alternatives:  %c##-##
+
+   A range of alternative numeric values can be specified compactly,
+   using a dash ("-") to indicate the range of alternative values.
+   Hence:
+
+         DIGIT       =  %x30-39
+
+   is equivalent to:
+
+         DIGIT       =  "0" / "1" / "2" / "3" / "4" / "5" / "6" /
+
+                        "7" / "8" / "9"
+
+   Concatenated numeric values and numeric value ranges cannot be
+   specified in the same string.  A numeric value may use the dotted
+   notation for concatenation or it may use the dash notation to specify
+   one value range.  Hence, to specify one printable character between
+   end-of-line sequences, the specification could be:
+
+         char-line = %x0D.0A %x20-7E %x0D.0A
+
+3.5.  Sequence Group:  (Rule1 Rule2)
+
+   Elements enclosed in parentheses are treated as a single element,
+   whose contents are strictly ordered.  Thus,
+
+         elem (foo / bar) blat
+
+   matches (elem foo blat) or (elem bar blat), and
+
+         elem foo / bar blat
+
+   matches (elem foo) or (bar blat).
+
+   NOTE:
+
+      It is strongly advised that grouping notation be used, rather than
+      relying on the proper reading of "bare" alternations, when
+      alternatives consist of multiple rule names or literals.
+
+   Hence, it is recommended that the following form be used:
+
+        (elem foo) / (bar blat)
+
+   It will avoid misinterpretation by casual readers.
+
+
+
+
+
+Crocker & Overell           Standards Track                     [Page 8]
+
+RFC 5234                          ABNF                      January 2008
+
+
+   The sequence group notation is also used within free text to set off
+   an element sequence from the prose.
+
+3.6.  Variable Repetition:  *Rule
+
+   The operator "*" preceding an element indicates repetition.  The full
+   form is:
+
+         <a>*<b>element
+
+   where <a> and <b> are optional decimal values, indicating at least
+   <a> and at most <b> occurrences of the element.
+
+   Default values are 0 and infinity so that *<element> allows any
+   number, including zero; 1*<element> requires at least one;
+   3*3<element> allows exactly 3; and 1*2<element> allows one or two.
+
+3.7.  Specific Repetition:  nRule
+
+   A rule of the form:
+
+         <n>element
+
+   is equivalent to
+
+         <n>*<n>element
+
+   That is, exactly <n> occurrences of <element>.  Thus, 2DIGIT is a
+   2-digit number, and 3ALPHA is a string of three alphabetic
+   characters.
+
+3.8.  Optional Sequence:  [RULE]
+
+   Square brackets enclose an optional element sequence:
+
+         [foo bar]
+
+   is equivalent to
+
+         *1(foo bar).
+
+3.9.  Comment:  ; Comment
+
+   A semicolon starts a comment that continues to the end of line.  This
+   is a simple way of including useful notes in parallel with the
+   specifications.
+
+
+
+
+
+Crocker & Overell           Standards Track                     [Page 9]
+
+RFC 5234                          ABNF                      January 2008
+
+
+3.10.  Operator Precedence
+
+   The various mechanisms described above have the following precedence,
+   from highest (binding tightest) at the top, to lowest (loosest) at
+   the bottom:
+
+      Rule name, prose-val, Terminal value
+
+      Comment
+
+      Value range
+
+      Repetition
+
+      Grouping, Optional
+
+      Concatenation
+
+      Alternative
+
+   Use of the alternative operator, freely mixed with concatenations,
+   can be confusing.
+
+      Again, it is recommended that the grouping operator be used to
+      make explicit concatenation groups.
+
+4.  ABNF Definition of ABNF
+
+   NOTES:
+
+      1.  This syntax requires a formatting of rules that is relatively
+          strict.  Hence, the version of a ruleset included in a
+          specification might need preprocessing to ensure that it can
+          be interpreted by an ABNF parser.
+
+      2.  This syntax uses the rules provided in Appendix B.
+
+
+         rulelist       =  1*( rule / (*c-wsp c-nl) )
+
+         rule           =  rulename defined-as elements c-nl
+                                ; continues if next line starts
+                                ;  with white space
+
+         rulename       =  ALPHA *(ALPHA / DIGIT / "-")
+
+
+
+
+
+
+Crocker & Overell           Standards Track                    [Page 10]
+
+RFC 5234                          ABNF                      January 2008
+
+
+         defined-as     =  *c-wsp ("=" / "=/") *c-wsp
+                                ; basic rules definition and
+                                ;  incremental alternatives
+
+         elements       =  alternation *c-wsp
+
+         c-wsp          =  WSP / (c-nl WSP)
+
+         c-nl           =  comment / CRLF
+                                ; comment or newline
+
+         comment        =  ";" *(WSP / VCHAR) CRLF
+
+         alternation    =  concatenation
+                           *(*c-wsp "/" *c-wsp concatenation)
+
+         concatenation  =  repetition *(1*c-wsp repetition)
+
+         repetition     =  [repeat] element
+
+         repeat         =  1*DIGIT / (*DIGIT "*" *DIGIT)
+
+         element        =  rulename / group / option /
+                           char-val / num-val / prose-val
+
+         group          =  "(" *c-wsp alternation *c-wsp ")"
+
+         option         =  "[" *c-wsp alternation *c-wsp "]"
+
+         char-val       =  DQUOTE *(%x20-21 / %x23-7E) DQUOTE
+                                ; quoted string of SP and VCHAR
+                                ;  without DQUOTE
+
+         num-val        =  "%" (bin-val / dec-val / hex-val)
+
+         bin-val        =  "b" 1*BIT
+                           [ 1*("." 1*BIT) / ("-" 1*BIT) ]
+                                ; series of concatenated bit values
+                                ;  or single ONEOF range
+
+         dec-val        =  "d" 1*DIGIT
+                           [ 1*("." 1*DIGIT) / ("-" 1*DIGIT) ]
+
+         hex-val        =  "x" 1*HEXDIG
+                           [ 1*("." 1*HEXDIG) / ("-" 1*HEXDIG) ]
+
+
+
+
+
+
+Crocker & Overell           Standards Track                    [Page 11]
+
+RFC 5234                          ABNF                      January 2008
+
+
+         prose-val      =  "<" *(%x20-3D / %x3F-7E) ">"
+                                ; bracketed string of SP and VCHAR
+                                ;  without angles
+                                ; prose description, to be used as
+                                ;  last resort
+
+5.  Security Considerations
+
+   Security is truly believed to be irrelevant to this document.
+
+6.  References
+
+6.1.  Normative References
+
+   [US-ASCII]  American National Standards Institute, "Coded Character
+               Set -- 7-bit American Standard Code for Information
+               Interchange", ANSI X3.4, 1986.
+
+6.2.  Informative References
+
+   [RFC733]    Crocker, D., Vittal, J., Pogran, K., and D. Henderson,
+               "Standard for the format of ARPA network text messages",
+               RFC 733, November 1977.
+
+   [RFC822]    Crocker, D., "Standard for the format of ARPA Internet
+               text messages", STD 11, RFC 822, August 1982.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                    [Page 12]
+
+RFC 5234                          ABNF                      January 2008
+
+
+Appendix A.  Acknowledgements
+
+   The syntax for ABNF was originally specified in RFC 733.  Ken L.
+   Harrenstien, of SRI International, was responsible for re-coding the
+   BNF into an Augmented BNF that makes the representation smaller and
+   easier to understand.
+
+   This recent project began as a simple effort to cull out the portion
+   of RFC 822 that has been repeatedly cited by non-email specification
+   writers, namely the description of Augmented BNF.  Rather than simply
+   and blindly converting the existing text into a separate document,
+   the working group chose to give careful consideration to the
+   deficiencies, as well as benefits, of the existing specification and
+   related specifications made available over the last 15 years, and
+   therefore to pursue enhancement.  This turned the project into
+   something rather more ambitious than was first intended.
+   Interestingly, the result is not massively different from that
+   original, although decisions, such as removing the list notation,
+   came as a surprise.
+
+   This "separated" version of the specification was part of the DRUMS
+   working group, with significant contributions from Jerome Abela,
+   Harald Alvestrand, Robert Elz, Roger Fajman, Aviva Garrett, Tom
+   Harsch, Dan Kohn, Bill McQuillan, Keith Moore, Chris Newman, Pete
+   Resnick, and Henning Schulzrinne.
+
+   Julian Reschke warrants a special thanks for converting the Draft
+   Standard version to XML source form.
+
+Appendix B.  Core ABNF of ABNF
+
+   This appendix contains some basic rules that are in common use.
+   Basic rules are in uppercase.  Note that these rules are only valid
+   for ABNF encoded in 7-bit ASCII or in characters sets that are a
+   superset of 7-bit ASCII.
+
+B.1.  Core Rules
+
+   Certain basic rules are in uppercase, such as SP, HTAB, CRLF, DIGIT,
+   ALPHA, etc.
+
+         ALPHA          =  %x41-5A / %x61-7A   ; A-Z / a-z
+
+         BIT            =  "0" / "1"
+
+         CHAR           =  %x01-7F
+                                ; any 7-bit US-ASCII character,
+                                ;  excluding NUL
+
+
+
+Crocker & Overell           Standards Track                    [Page 13]
+
+RFC 5234                          ABNF                      January 2008
+
+
+         CR             =  %x0D
+                                ; carriage return
+
+         CRLF           =  CR LF
+                                ; Internet standard newline
+
+         CTL            =  %x00-1F / %x7F
+                                ; controls
+
+         DIGIT          =  %x30-39
+                                ; 0-9
+
+         DQUOTE         =  %x22
+                                ; " (Double Quote)
+
+         HEXDIG         =  DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
+
+         HTAB           =  %x09
+                                ; horizontal tab
+
+         LF             =  %x0A
+                                ; linefeed
+
+         LWSP           =  *(WSP / CRLF WSP)
+                                ; Use of this linear-white-space rule
+                                ;  permits lines containing only white
+                                ;  space that are no longer legal in
+                                ;  mail headers and have caused
+                                ;  interoperability problems in other
+                                ;  contexts.
+                                ; Do not use when defining mail
+                                ;  headers and use with caution in
+                                ;  other contexts.
+
+         OCTET          =  %x00-FF
+                                ; 8 bits of data
+
+         SP             =  %x20
+
+         VCHAR          =  %x21-7E
+                                ; visible (printing) characters
+
+         WSP            =  SP / HTAB
+                                ; white space
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                    [Page 14]
+
+RFC 5234                          ABNF                      January 2008
+
+
+B.2.  Common Encoding
+
+   Externally, data are represented as "network virtual ASCII" (namely,
+   7-bit US-ASCII in an 8-bit field), with the high (8th) bit set to
+   zero.  A string of values is in "network byte order", in which the
+   higher-valued bytes are represented on the left-hand side and are
+   sent over the network first.
+
+Authors' Addresses
+
+   Dave Crocker (editor)
+   Brandenburg InternetWorking
+   675 Spruce Dr.
+   Sunnyvale, CA  94086
+   US
+
+   Phone: +1.408.246.8253
+   EMail: dcrocker@bbiw.net
+
+
+   Paul Overell
+   THUS plc.
+   1/2 Berkeley Square,
+   99 Berkeley Street
+   Glasgow  G3 7HR
+   UK
+
+   EMail: paul.overell@thus.net
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                    [Page 15]
+
+RFC 5234                          ABNF                      January 2008
+
+
+Full Copyright Statement
+
+   Copyright (C) The IETF Trust (2008).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
+   such proprietary rights by implementers or users of this
+   specification can be obtained from the IETF on-line IPR repository at
+   http://www.ietf.org/ipr.
+
+   The IETF invites any interested party to bring to its attention any
+   copyrights, patents or patent applications, or other proprietary
+   rights that may cover technology that may be required to implement
+   this standard.  Please address the information to the IETF at
+   ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell           Standards Track                    [Page 16]
+