[Svn] RFC3501 [7.1] optional CAPABILITY response

Eric Stadtherr estadtherr at gmail.com
Sat May 17 21:09:11 CEST 2008

On Sat, 17 May 2008 20:16:39 +0200, Thomas Bruederli <roundcube at gmail.com>
> Hello again
> Since revision 1368, the separate call for capabilities is omitted, if
> welcome message of the IMAP server already contains CAPABILITY.
> Unfortunately my IMAP server (uw-imap) does return a CAPABILITY section 
> right away but this is not complete and differs from the one that is 
> returned when issuing the CAPABILITY command.
> I recognized this because I could not sort the message list anymore which

> was possible with previous versions of RoundCube.
> What do you think, should we revert this? I know that uw-imap probably
> does 
> not behave the way is should but this change breaks RoundCube seriously.

The RFC is not 100% clear in this instance. It seems that the CAPABILITY
set is allowed to change during a session. For example, after a STARTTLS
exchange completes, the set of allowed authentication mechanisms is allowed
to change. Perhaps UW-IMAP changes the overall capability set after the
user is authenticated, which does not seem to be explicitly forbidden by
the RFC.

Given this discovery, it seems safest to just go ahead and explicitly
request CAPABILITY after the initialization is completed. This is
admittedly one more round trip to the server, but who knows what other
capabilities might be missing from the optional initial set in other

> ~Thomas
> _______________________________________________
> http://lists.roundcube.net/mailman/listinfo/svn
Eric Stadtherr
estadtherr at gmail.com


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