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Versions: 00 01 02 03 04 05 RFC 4469

LEMONADE                                                      P. Resnick
Internet-Draft                                     QUALCOMM Incorporated
Expires: August 20, 2005                               February 16, 2005


       Internet Message Access Protocol (IMAP) CATENATE Extension
                    draft-ietf-lemonade-catenate-04

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   The CATENATE extension to the Internet Message Access Protocol (IMAP)
   modifies the APPEND command to allow clients to create messages on
   the IMAP server which 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 on to a new message without having to first download the data
   and then upload it back to the server.



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1.  Introduction

   The CATENATE extension to the Internet Message Access Protocol (IMAP)
   [1] allows the client to create a message on the server which 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 modifies 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 of the pieces and catenates
   them into the output message.  The CATENATE extension can also
   co-exist 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 which 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
   the 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
   of the scope of this document.)

   The new 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 including other data by making a
   copy of the original and catenating the new data.

2.  The CATENATE Capability

   A server which supports this extension returns "CATENATE" as one of
   the responses to the CAPABILITY command.

3.  The APPEND command

   Arguments:     mailbox name
                  (The following can be repeated in the presence of the
                  MULTIAPPEND extension [3])





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                  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 of 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 old 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 new form is used, the token "CATENATE"
   and a parenthesized list of message literals and message URLs
   follows, each of which are appended to the new message.  If a message
   literal is specified (indicated by the "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.

      Note: This document only describes the behavior of the APPEND
      command using message URLs (as defined by [2]) which refer to
      specific messages or message parts on the current IMAP server.
      Use of a URL that refers to anything other than a message or
      message part on the current IMAP server is outside of the scope of
      this document, 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 RFC 2822 [4] message.  This includes inserting
   appropriate MIME [5] boundaries between body parts if necessary.




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   Responses behave just as the 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 which 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, 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.

4.2  TOOBIG Response

   The TOOBIG response code is returned if the resulting message will
   exceed the 4Gb IMAP message limit.  This might happen, for example,
   if the client specifies 3 URLs for 2Gb 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 4Gb limit.  The server may also wish to return the
   TOOBIG response code if the resulting message exceeds the server
   specific message size limit.





















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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] and IMAP [1] specifications.  Note
   that resp-text-code is extended from original IMAP [1] specification.

   append = "APPEND" SP mailbox 1*append-message
               ; only a single append-message may appear
               ; if MULTIAPPEND capability is not present

   append-message = append-opts SP (literal / append-catenate)

   append-opts = [SP flag-list] [SP date-time]

   append-catenate = "CATENATE" SP "(" catenate-parts ")"

   catenate-parts = (text-literal / url) *(SP (text-literal / url))

   text-literal = "TEXT" SP literal

   url = "URL" SP astring

   badurl_response_code = "BADURL" SP url-resp-text

   url-resp-text = 1*(%x01-09 /
                      %x0B-0C /
                      %x0E-5B /
                      %x5D-FE) ; Any TEXT-CHAR except "]"

   toobig_response_code = "TOOBIG"

   resp-text-code =/ badurl_response_code / toobig_response_code

   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].

6.  Acknowledgments

   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]



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   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.  IANA is requested to add this
   capability to the registry.

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 "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/;
    UID=20;section=HEADER" TEXT {40}
   S: + Ready for literal data
   C: --------------030308070208000400050907
   C:  URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/;
    UID=20;section=1.MIME" URL "imap://imap.example.org/Drafts;
    UIDVALIDITY=385759045/;UID=20;section=1" TEXT {40}
   S: + Ready for literal data
   C: --------------030308070208000400050907
   C:  URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/;
    UID=30" {44}
   S: + Ready for literal data
   C: --------------030308070208000400050907--
   C: )
   S: A003 OK catenate append completed










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   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 "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/;
    UID=20;Section=2.MIME" URL "imap://imap.example.org/Drafts;
    UIDVALIDITY=385759045/;UID=20;Section=2" TEXT {44}
   S: + Ready for literal data
   C: --------------030308070208000400050907--
   C: )
   S: A003 OK [APPENDUID 385759045 45] append Completed
   C: A004 UID STORE 20 +FLAGS.SILENT (\Deleted)
   S: A004 OK STORE completed









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   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 "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/;
    UID=21;section=HEADER" TEXT {40}
   S: + Ready for literal data
   C: --------------030308070208000400050903
   C:  URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/;
    UID=21;section=1.MIME" URL "imap://imap.example.org/Drafts;
    UIDVALIDITY=385759045/;UID=21;section=1" TEXT {255}
   S: + Ready for literal data
   C: --------------030308070208000400050903
   C: Content-type: text/plain; charset="us-ascii"
   C: Content-transfer-encoding: 7bit
   C:
   C: This bodypart contained a Power Point presentation, that was
   C: deleted upon your request.
   C: --------------030308070208000400050903--
   C: )
   S: A003 OK append Completed




























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   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 "imap://imap.example.org/INBOX;UIDVALIDITY=785799047/;
    UID=11467" TEXT {40}
   S: + Ready for literal data
   C: --------------030308070208000400050904
   C:  URL "imap://imap.example.org/INBOX;UIDVALIDITY=785799047/;
    UID=113330;section=1.5.9" TEXT {40}
   S: + Ready for literal data
   C: --------------030308070208000400050904
   C:  URL "imap://imap.example.org/INBOX;UIDVALIDITY=785799047/;
    UID=11916" TEXT {44}
   S: + Ready for literal data
   C: --------------030308070208000400050904--
   C: )
   S: A003 NO [BADURL "imap://imap.example.org/INBOX;UIDVALIDITY=785799047/
    ;UID=113330;section=1.5.9"] CATENATE append has failed, one message expunged


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) -



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        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]  Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June 1998.

   [7]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.


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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