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Network Working Group                                         P. ResnickRequest for Comments: 4469                         QUALCOMM IncorporatedUpdates:3501,3502                                           April 2006Category: Standards TrackInternet Message Access Protocol (IMAP) CATENATE ExtensionStatus 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.Resnick                     Standards Track                     [Page 1]

RFC 4469                IMAP CATENATE Extension               April 20061.  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 20063.  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 URLResnick                     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 inSection 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 20064.2.  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 20066.  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.Resnick                     Standards Track                     [Page 6]

RFC 4469                IMAP CATENATE Extension               April 2006Appendix 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 completedResnick                     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 completedResnick                     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 CompletedResnick                     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 20069.  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.Resnick                     Standards Track                    [Page 11]

RFC 4469                IMAP CATENATE Extension               April 2006Author'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/Resnick                     Standards Track                    [Page 12]

RFC 4469                IMAP CATENATE Extension               April 2006Full Copyright Statement   Copyright (C) The Internet Society (2006).   This document is subject to the rights, licenses and restrictions   contained inBCP 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 inBCP 78 andBCP 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 athttp://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]