The IMAP ENABLE Extension
RFC 5161
| Document | Type |
RFC - Proposed Standard
(March 2008; No errata)
Was draft-gulbrandsen-imap-enable (individual in app area)
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 5161 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Chris Newman | ||
| Send notices to | (None) | ||
Network Working Group A. Gulbrandsen, Ed.
Request for Comments: 5161 Oryx Mail Systems GmbH
Category: Standards Track A. Melnikov, Ed.
Isode Limited
March 2008
The IMAP ENABLE Extension
Status 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.
Abstract
Most IMAP extensions are used by the client when it wants to and the
server supports it. However, a few extensions require the server to
know whether a client supports that extension. The ENABLE extension
allows an IMAP client to say which extensions it supports.
1. Overview
Several IMAP extensions allow the server to return unsolicited
responses specific to these extensions in certain circumstances.
However, servers cannot send those unsolicited responses until they
know that the clients support such extensions and thus won't choke on
the extension response data.
Up until now, extensions have typically stated that a server cannot
send the unsolicited responses until after the client has used a
command with the extension data (i.e., at that point the server knows
the client is aware of the extension). CONDSTORE ([RFC4551]),
ANNOTATE ([ANNOTATE]), and some extensions under consideration at the
moment use various commands to enable server extensions. For
example, CONDSTORE uses a SELECT or FETCH parameter, and ANNOTATE
uses a side effect of FETCH.
The ENABLE extension provides an explicit indication from the client
that it supports particular extensions. This is done using a new
ENABLE command.
An IMAP server that supports ENABLE advertises this by including the
word ENABLE in its capability list.
Gulbrandsen & Melnikov Standards Track [Page 1]
RFC 5161 The IMAP ENABLE Extension March 2008
Most IMAP extensions do not require the client to enable the
extension in any way.
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Formal syntax is defined by [RFC5234] and [RFC3501].
Example lines prefaced by "C:" are sent by the client and ones
prefaced by "S:" by the server. The five characters [...] means that
something has been elided.
3. Protocol Changes
3.1. The ENABLE Command
Arguments: capability names
Result: OK: Relevant capabilities enabled
BAD: No arguments, or syntax error in an argument
The ENABLE command takes a list of capability names, and requests the
server to enable the named extensions. Once enabled using ENABLE,
each extension remains active until the IMAP connection is closed.
For each argument, the server does the following:
- If the argument is not an extension known to the server, the server
MUST ignore the argument.
- If the argument is an extension known to the server, and it is not
specifically permitted to be enabled using ENABLE, the server MUST
ignore the argument. (Note that knowing about an extension doesn't
necessarily imply supporting that extension.)
- If the argument is an extension that is supported by the server and
that needs to be enabled, the server MUST enable the extension for
the duration of the connection. At present, this applies only to
CONDSTORE ([RFC4551]). Note that once an extension is enabled,
there is no way to disable it.
If the ENABLE command is successful, the server MUST send an untagged
ENABLED response (see Section 3.2).
Gulbrandsen & Melnikov Standards Track [Page 2]
RFC 5161 The IMAP ENABLE Extension March 2008
Clients SHOULD only include extensions that need to be enabled by the
server. At the time of publication, CONDSTORE is the only such
extension (i.e., ENABLE CONDSTORE is an additional "CONDSTORE
enabling command" as defined in [RFC4551]). Future RFCs may add to
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