[Dovecot] dovecot imap auth fails to reconnect pgsql backend

[Frank Wang]

> Hi,
>     We've observed frequent auth failure recently from the SquirrelMail
> frontend. The imap server is the dovecot-1.0.7-2 from Centos 5.2. The
> auth backend is a pgsql database on another server. The only way to make
> it work is to restart the dovecot, though sometimes it'll recover
> automatically, but you don't know when. At first we thought there might
> be a network problem, but we can always run pgsql client from the
> dovecot server to connect and query the backend database during the auth
> failure. We then upgraded to dovecot-1.1.3 from atrpms.net yesterday,
> and still the same. It looks like the dovecot fails to reconnect/retry
> pgsql backend.
It's the router, a H3C Quidway AR28-31 with the latest firmware VRP3.4
F0306p06, caused the problem. We upgraded it last week and found part of
the database connection from the mail server were blocked by the
firewall in the DB server syslog because of the bad tcp state. After
revert the firmware, mail server auth act normal again. 

Regards,
Frank Wang