LEMONADE P. Resnick
Internet-Draft QUALCOMM Incorporated
Expires: June 29, 2004 December 30, 2003
Internet Message Access Protocol (IMAP) CATENATE Extension
draft-ietf-lemonade-catenate-01
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The CATENATE extension to the Internet Message Access Protocol (IMAP)
allows 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 command works much like the APPEND
command except 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.
There are some obvious uses for the CATENATE command. The motivating
use case for this command was to provide a way for a
resource-constrained client to compose a message for future delivery
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. (Mechanisms for sending the message are
outside of the scope of this document.)
CATENATE 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. CATENATE 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.
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2. The CATENATE Capability
A server which supports this extension returns "CATENATE" as one of
the responses to the CAPABILITY command.
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3. The CATENATE command
Arguments: mailbox name
OPTIONAL flag parenthesized list
OPTIONAL date/time string
one or more message parts to catenate, specified as:
message literal
or
message (or message part) URL
Responses: no specific responses for this command
Result:
OK - catenate completed
NO - catenate 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 CATENATE command concatenates all of the message parts and
appends them as a new message to the end of the specified mailbox.
The optional flag parenthesized list and date/time string are used
just as they are in the APPEND command, setting the flags and the
internal date, respectively. The subsequent parameters specify the
message parts that are appended sequentially to the output message.
If a message literal is specified (indicated by the octet count
enclosed in braces), the octets following the count are appended just
as they would be with the APPEND command. If a message URL is
specified, the octets of that body part are appended, as if the
literal returned in a FETCH BODY response were put in place of the
message part specifier. The CATENATE command does not cause the \Seen
flag to be set for any catenated body part.
Note: This document only describes the behavior of the CATENATE
command using a message URL (as defined by [2]) which refers to a
specific message or message part in the currently selected mailbox
on the current IMAP server. (Because of that, the CATENATE command
is valid in the selected state for purposes of this
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specification.) Use of a URL that refers to anything other than a
message or message part from the currently selected mailbox 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 [3] message. This includes inserting
appropriate MIME [4] boundaries between body parts if necessary.
Responses behave just as the APPEND command. If the server implements
the IMAP UIDPLUS extension [5], it will also return an APPENDUID
response code in the tagged OK response.
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4. Formal Syntax
The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) [6] notation. Undefined elements are defined in the
formal syntax of the ABNF [6], IMAP [1], and IMAP URL [2]
specifications.
catenate = "CATENATE" SP mailbox [SP flag-list] [SP date-time]
1*(SP (literal / imapurl))
Figure 1
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5. 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.
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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] Resnick, P., "Internet Message Format", RFC 2822, April 2001.
[4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, November 1996.
[5] Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June 1998.
[6] Crocker, D. 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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