Protocol Action: 'IMAP4 LIST Command Extensions' to Proposed Standard

The IESG has approved the following document:

- 'IMAP4 LIST Command Extensions '
   <draft-ietf-imapext-list-extensions-18.txt> as a Proposed Standard

This document is the product of the Internet Message Access Protocol 
Extension Working Group. 

The IESG contact persons are Lisa Dusseault and Ted Hardie.

A URL of this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-imapext-list-extensions-18.txt

Technical Summary

IMAP4 [RFC 3501] has two commands for listing mailboxes: LIST and LSUB.
Unfortunately, these commands are not extensible: As extensions requiring
specialized lists have been added to IMAP, new list commands have to be
added toinclude the functions of both LIST and LSUB. If the extensions
need to work together with other commands, a set of commands mixing the
different options must be added, increasing the size of the set with each
new extension. This document describes an extension to the base LIST
command that will allow these additions to be done with mutually
compatible options to the LIST command, avoiding the exponential increase
in specialized list commands. It extends the allowable options in the LIST
command itself as well as extending the allowable return options. The new
options allow for the return of information for the Child Mailbox
Extension [RFC 33480] as well as providing functionality to replace (and
eventually deprecate) the Mailbox Referrals RLIST and RLSUB
commands [RFC 2193].

Working Group Summary

This document is a product of the IMAP Extensions (IMAPEXT) Working Group.
This document has received *extensive* review in the working group.
However, unlike some documents that might have gone through 17 versions
over the course of 5+ years, this document does in fact seem to be the
product of good working group consensus, not simply working group
exhaustion. It took quite a long time and several versions for the working
group to settle on the right balance between richness of functionality
(e.g., in different properties that could be requestedand returned) and
the ease of implementation. As new working group members have come on
board over the years with new IMAP client and server implementations,
features were tuned to accommodate those implementors. Approximately
half-a-dozen implementations of the spec (including both servers and
clients) have been implemented to date and corrections to the document
have been made in response. Overall, the working group is quite happy with
the results.

Protocol Quality

Pete Resnick, IMAP Extensions (IMAPEXT) working group chair, and Lisa
Dusseault,reviewed this document for the IESG.

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