7Network Working Group M. Crispin
8Request for Comments: 3502 University of Washington
9Category: Standards Track March 2003
12 Internet Message Access Protocol (IMAP) - MULTIAPPEND Extension
16 This document specifies an Internet standards track protocol for the
17 Internet community, and requests discussion and suggestions for
18 improvements. Please refer to the current edition of the "Internet
19 Official Protocol Standards" (STD 1) for the standardization state
20 and status of this protocol. Distribution of this memo is unlimited.
24 Copyright (C) The Internet Society (2003). All Rights Reserved.
28 This document describes the multiappending extension to the Internet
29 Message Access Protocol (IMAP) (RFC 3501). This extension provides
30 substantial performance improvements for IMAP clients which upload
31 multiple messages at a time to a mailbox on the server.
33 A server which supports this extension indicates this with a
34 capability name of "MULTIAPPEND".
38 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
39 "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
40 be interpreted as described in [KEYWORDS].
44 The MULTIAPPEND extension permits uploading of multiple messages with
45 a single command. When used in conjunction with the [LITERAL+]
46 extension, the entire upload is accomplished in a single
47 command/response round trip.
49 A MULTIAPPEND APPEND operation is atomic; either all messages are
50 successfully appended, or no messages are appended.
52 In the base IMAP specification, each message must be appended in a
53 separate command, and there is no mechanism to "unappend" messages if
54 an error occurs while appending. Also, some mail stores may require
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60RFC 3502 IMAP MULTIAPPEND March 2003
63 an expensive "open/lock + sync/unlock/close" operation as part of
64 appending; this can be quite expensive if it must be done on a
67 If the server supports both LITERAL+ and pipelining but not
68 MULTIAPPEND, it may be possible to get some of the performance
69 advantages of MULTIAPPEND by doing a pipelined "batch" append.
70 However, it will not work as well as MULTIAPPEND for the following
73 1) Multiple APPEND commands, even as part of a pipelined batch,
74 are non-atomic by definition. There is no way to revert the
75 mailbox to the state before the batch append in the event of an
78 2) It may not be feasible for the server to coalesce pipelined
79 APPEND operations so as to avoid the "open/lock +
80 sync/unlock/close" overhead described above. In any case, such
81 coalescing would be timing dependent and thus potentially
82 unreliable. In particular, with traditional UNIX mailbox files,
83 it is assumed that a lock is held only for a single atomic
84 operation, and many applications disregard any lock that is
87 3) If an error occurs, depending upon the nature of the error,
88 it is possible for additional messages to be appended after the
89 error. For example, the user wants to append 5 messages, but a
90 disk quota error occurs with the third message because of its
91 size. However, the fourth and fifth messages have already been
92 sent in the pipeline, so the mailbox ends up with the first,
93 second, fourth, and fifth messages of the batch appended.
97 Arguments: mailbox name
98 one or more messages to upload, specified as:
99 OPTIONAL flag parenthesized list
100 OPTIONAL date/time string
103 Data: no specific responses for this command
105 Result: OK - append completed
106 NO - append error: can't append to that mailbox, error
107 in flags or date/time or message text,
109 BAD - command unknown or arguments invalid
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116RFC 3502 IMAP MULTIAPPEND March 2003
119 The APPEND command appends the literal arguments as new messages
120 to the end of the specified destination mailbox. This argument
121 SHOULD be in the format of an [RFC-2822] message. 8-bit
122 characters are permitted in the message. A server implementation
123 that is unable to preserve 8-bit data properly MUST be able to
124 reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB]
125 content transfer encoding.
127 Note: There MAY be exceptions, e.g., draft messages, in
128 which required [RFC-2822] header lines are omitted in the
129 message literal argument to APPEND. The full implications
130 of doing so MUST be understood and carefully weighed.
132 If a flag parenthesized list is specified, the flags SHOULD be set
133 in the resulting message; otherwise, the flag list of the
134 resulting message is set empty by default.
136 If a date-time is specified, the internal date SHOULD be set in
137 the resulting message; otherwise, the internal date of the
138 resulting message is set to the current date and time by default.
140 A zero-length message literal argument is an error, and MUST
141 return a NO. This can be used to cancel the append.
143 If the append is unsuccessful for any reason (including being
144 cancelled), the mailbox MUST be restored to its state before the
145 APPEND attempt; no partial appending is permitted. The server MAY
146 return an error before processing all the message arguments.
148 If the destination mailbox does not exist, a server MUST return an
149 error, and MUST NOT automatically create the mailbox. Unless it
150 is certain that the destination mailbox can not be created, the
151 server MUST send the response code "[TRYCREATE]" as the prefix of
152 the text of the tagged NO response. This gives a hint to the
153 client that it can attempt a CREATE command and retry the APPEND
154 if the CREATE is successful.
156 If the mailbox is currently selected, the normal new message
157 actions SHOULD occur. Specifically, the server SHOULD notify the
158 client immediately via an untagged EXISTS response. If the server
159 does not do so, the client MAY issue a NOOP command (or failing
160 that, a CHECK command) after one or more APPEND commands.
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172RFC 3502 IMAP MULTIAPPEND March 2003
175 Example: C: A003 APPEND saved-messages (\Seen) {329}
176 S: + Ready for literal data
177 C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
178 C: From: Fred Foobar <foobar@Blurdybloop.example.COM>
179 C: Subject: afternoon meeting
180 C: To: mooch@owatagu.example.net
181 C: Message-Id: <B27397-0100000@Blurdybloop.example.COM>
183 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
185 C: Hello Joe, do you think we can meet at 3:30 tomorrow?
186 C: (\Seen) " 7-Feb-1994 22:43:04 -0800" {295}
187 S: + Ready for literal data
188 C: Date: Mon, 7 Feb 1994 22:43:04 -0800 (PST)
189 C: From: Joe Mooch <mooch@OWaTaGu.example.net>
190 C: Subject: Re: afternoon meeting
191 C: To: foobar@blurdybloop.example.com
192 C: Message-Id: <a0434793874930@OWaTaGu.example.net>
194 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
196 C: 3:30 is fine with me.
198 S: A003 OK APPEND completed
199 C: A004 APPEND bogusname (\Flagged) {1023}
200 S: A004 NO [TRYCREATE] No such mailbox as bogusname
201 C: A005 APPEND test (\Flagged) {99}
202 S: + Ready for literal data
203 C: Date: Mon, 7 Feb 2000 22:43:04 -0800 (PST)
204 C: From: Fred Foobar <fred@example.com>
207 S: A005 NO APPEND failed: Disk quota exceeded
209 Note: The APPEND command is not used for message delivery,
210 because it does not provide a mechanism to transfer [SMTP]
211 envelope information.
213Modification to IMAP4rev1 Base Protocol Formal Syntax
215 The following syntax specification uses the Augmented Backus-Naur
216 Form (ABNF) notation as specified in [ABNF].
218 append = "APPEND" SP mailbox 1*append-message
220 append-message = [SP flag-list] [SP date-time] SP literal
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228RFC 3502 IMAP MULTIAPPEND March 2003
231MULTIAPPEND Interaction with UIDPLUS Extension
233 Servers which support both MULTIAPPEND and [UIDPLUS] will have the
234 "resp-code-apnd" rule modified as follows:
236 resp-code-apnd = "APPENDUID" SP nz-number SP set
238 That is, the APPENDUID response code returns as many UIDs as there
239 were messages appended in the multiple append. The UIDs returned
240 should be in the order the articles where appended. The message set
241 may not contain extraneous UIDs or the symbol "*".
243Security Considerations
245 The MULTIAPPEND extension does not raise any security considerations
246 that are not present in the base [IMAP] protocol, and these issues
247 are discussed in [IMAP]. Nevertheless, it is important to remember
248 that IMAP4rev1 protocol transactions, including electronic mail data,
249 are sent in the clear over the network unless protection from
250 snooping is negotiated, either by the use of STARTTLS, privacy
251 protection is negotiated in the AUTHENTICATE command, or some other
252 protection mechanism is in effect.
256 [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
257 Specifications: ABNF", RFC 2234, November 1997.
259 [IMAP] Crispin, M., "Internet Message Access Protocol - Version
260 4rev1", RFC 3501, March 2003.
262 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
263 Requirement Levels", BCP 14, RFC 2119, March 1997.
265 [MIME-IMB] Freed, N. and N. Borenstein, "MIME (Multipurpose Internet
266 Mail Extensions) Part One: Format of Internet Message
267 Bodies", RFC 2045, November 1996.
269 [RFC-2822] Resnick, P., "Internet Message Format", RFC 2822, April
282Crispin Standards Track [Page 5]
284RFC 3502 IMAP MULTIAPPEND March 2003
287Informative References
289 [LITERAL+] Myers, J., "IMAP4 non-synchronizing literals", RFC 2088,
292 [UIDPLUS] Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June 1988.
294 [SMTP] Klensin, J., Editor, "Simple Mail Transfer Protocol", RFC
300 Networks and Distributed Computing
301 University of Washington
303 Seattle, WA 98105-4527
305 Phone: (206) 543-5762
306 EMail: MRC@CAC.Washington.EDU
338Crispin Standards Track [Page 6]
340RFC 3502 IMAP MULTIAPPEND March 2003
343Full Copyright Statement
345 Copyright (C) The Internet Society (2003). All Rights Reserved.
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