Possible IMAP IDLE bug in Dovecot 2.2.18 and 2.2.25

[The Doctor]

On Wed, Aug 24, 2016 at 12:49:02PM +0300, Timo Sirainen wrote:
> On 23 Aug 2016, at 15:08, cleber-listas at inetweb.com.br wrote:
> > 
> > Hello Guys,
> > I guess that I found a bug in Dovecot 2.2.18 and 2.2.25 versions. The 
> > problem it's when I try to connect in a Dovecot used a proxy to another 
> > e-mail server (in our case it's a Smartermail Server) the DoveCot send a 
> > lot of IDLE commands to the destination server. With that, the LOG files 
> > grow and grow and grow :(
> > 
> > I make a test with 1 connection only and if you see the log file in the 
> > same second the dovecot send 25, 40 IDLE commands. But, when I disconnect 
> > the client (outlook 2013) the dovecot continue to send the IDLE command for 
> > some seconds.
> 
> After login Dovecot proxy no longer understands anything about the traffic. It simply keeps proxying the IMAP traffic between the client and server. So Dovecot isn't the one generating the IDLE commands, it's Outlook.
> 
> > If I try to connect directly to Smartermail with Outlook this don't 
> > occurrs.
> 
> That is stranger then. Maybe it has something to do with having a different CAPABILITY response. You could try setting imap_capability setting to same as what Smartermail announces. Other than that I can't really think of anything specific that you could do or we could fix on Dovecot code.

Older Outlook client software is simply just not keeping
up to standard.  Unless M$ cares to remove SSL2 and SSL3 
support from their software, it is easier just to update
your client e-mail software which is more current and compliant
to recent 2015+ standarnds.

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