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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] + |