[Dovecot] Capability info in hello message not complete?

[Timo Sirainen]

On Thu, 2009-10-01 at 14:59 +0200, Michal Hlavinka wrote:
> Hi,
> 
> one Fedora user complains about not some troubles after update to dovecot 1.2. 
> He suspects wrong capability information given by dovecot 1.2
> 
> In dovecot.conf he uses imap_capability= option. While response to 'A 
> CAPABILITY' respects imap_capability value, the capability info in hello 
> message does not.
> 
> for imap_capability=IMAP4 IMAP4rev1 ACL NAMESPACE CHILDREN SORT QUOTA 
> THREAD=ORDEREDSUBJECT UNSELECT IDLE STARTTLS AUTH=PLAIN

I suppose he's using Dovecot as a proxy? Because Dovecot doesn't support
IMAP4 or THREAD=ORDEREDSUBJECT.

> but hello message is:
> * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE STARTTLS 
> AUTH=PLAIN] Dovecot ready.

Hmm. Yeah..

> But it seems even when imap_capability is not used capability in hello message 
> is not complete:
..
> is this expected? Do you think capability information in hello message really 
> can befool clients?

The capability in greeting message is short on purpose. It's only enough
capabilities to get client logged in. After login Dovecot sends an
updated full capability list to the client. It uses a few different
tricks to get most clients understand the change.

So the only potential problem I see here is if client understands the
greeting capability and permanently remembers that the server supports
LITERAL+, ID and ENABLE after login but the destination server actually
doesn't. The other capabilities are relevant only before login. I'm not
entirely sure what, if anything, I should do about this.

I'd anyway like to hear what exactly is the problem and with what
client, preferably with IMAP traffic logs showing what's happening
wrong.
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