[Dovecot] Problems with the IMAP proxy after upgrading from dovecot 1.1.16 to 1.211

[Holger Richter]

>> May  7 14:47:42 ttt dovecot: auth(default):   
>> worker-server(uid,yyy.yyy.yyy.yyy): Aborted: Lookup timed out
>> May  7 14:47:42 ttt dovecot: auth-worker(default): mysql: Connected to
>> lll.lll.lll.lll (imapauth)
>
> "Lookup timed out" really shouldn't be happening.. That sounds like
> Dovecot's MySQL connections hangs after a while? You have some stateful
> firewall between Dovecot and MySQL that drops idling connections and
> afterwards starts dropping the connection's packets?

Indeed, there is a firewall with stateful inspection between Dovecot  
and MySQL. The only workaround is a downgrade to Dovecot 1.1.20. I  
think my problem has to do with the changes in  
src/auth/auth-worker-server.c in changeset 8859.