Network Working Group M. Crispin INTERNET DRAFT: IMAP UIDPLUS extension May 2005 Document: internet-drafts/draft-crispin-imap-rfc2359bis-00.txt Internet Message Access Protocol (IMAP) - UIDPLUS extension Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html A revised version of this document will be submitted to the RFC editor as an Informational Document for the Internet Community. A revised version of this draft document will be submitted to the RFC editor as a Proposed Standard for the Internet Community. Discussion and suggestions for improvement are requested, and should be sent to imapext@IMC.ORG. This document will expire before 18 November 2005. Distribution of this memo is unlimited. 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. 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", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [KEYWORDS]. Introduction and Overview The UIDPLUS extension is present in any IMAP server implementation which 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 which 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 the same functionality, albeit less efficiently, by using facilities in the base protocol. 1. Additional Commands The following command definition is an extension to [IMAP] section 6.4. 1.1 UID EXPUNGE Command Arguments: message 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 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 is has a UID that is not included in the specified message set, it is not affected. This command may be used to ensure that a replayed EXPUNGE command does not remove any messages that have been marked as \Deleted between the time that the user requested the expunge operation and the time the server processes the command. 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. The client could alternatively fall back to using the EXPUNGE command, risking the unintended removal of some messages. Example: C: A003 UID EXPUNGE 3000:3002 S: * 3 EXPUNGE S: * 3 EXPUNGE S: * 3 EXPUNGE S: A003 OK UID EXPUNGE completed 2. Additional Response Codes The following response codes are extensions to the response codes defined in [IMAP] section 7.1. [IMAP] server implementations SHOULD return these response codes. A server which supports the UIDPLUS capability MUST return the APPENDUID or COPYUID response code as part of the tagged OK response to an APPEND or COPY command. The exception is if the destination mailbox that has UIDNOTSTICKY status; in that case, the server MAY omit the APPENDUID or COPYUID response as it is not meaningful. If the server does not return these 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. A server can determine that a mailbox does not support persistent UIDs by observing that the UIDVALIDITY changes with multiple selects of the mailbox. 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, then the second value is a message set containing the UIDs assigned to the appended messages, in the order they were assigned. This message set may not contain extraneous UIDs or the symbol "*". This response code is returned in a tagged OK response to the APPEND command. COPYUID Followed by the UIDVALIDITY of the destination mailbox, a message set containing the UIDs of the message(s) in the source mailbox which were copied to the destination mailbox, and a message set 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 message set is in the order the message(s) were copied; the destination message set corresponds to the source message set and is in the order the UID(s) were assigned. Neither of the message sets may contain extraneous UIDs or the symbol "*". This response code is returned in a tagged OK response to the COPY command. UIDNOTSTICKY The selected mailbox is supported by a mail store which 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 persistant UIDs. This should be avoided when designing new mail stores. Example: C: A003 APPEND saved-messages (\Seen) {297} C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST) C: From: Fred Foobar C: Subject: afternoon meeting C: To: mooch@example.com C: Message-Id: 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 for this session 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 which 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 305 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. 5. 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]: resp_code_apnd = "APPENDUID" SP nz_number SP append-uid append-uid = uniqueid resp_code_copy = "COPYUID" SP nz_number SP uid-set SP uid-set uid_expunge = "UID" SP "EXPUNGE" SP sequence-set uid-set = (uniqueid / uid-range) *("," uid-set) uid-range = (uid-number ":" uid-number) ; two uniquid values and all values between ; these two regards of order. ; Example: 2:4 and 4:2 are equivalent. Servers which support [MULTIAPPEND] will have the following extension to the above rules: append-uid =/ uid-set 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. [RFC-2822] Resnick, P., "Internet Message Format", RFC 2822, April 2001. Informative References [MULTIAPPEND] Crispin, M., "Internet Message Access Protocol (IMAP) - MULTIAPPEND Extension", RFC 3502, March 2003. 7. Security Considerations There are no known security issues with this extension. 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 IPR Disclosure Acknowledgement By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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