[Dovecot] dovecot ssl problem

[Alexander Heuer]

Hi there,
I am having a weird problem with dovecot and ssl.
If I am accessing the dovecot imap server with for example sylpheed-claws or evolution, everything works fine. If it is accessed via windows either by outlook or thunderbird, we get occassional timeouts.
It's working fine for a few hours, then for 5 to 20 minutes, every attempt to connect from the outside results in "Connection to server timed out". Added to that, the problem only arises, if a direct SSL connection to Port 993 is used. Using Sylpheed with STARTTLS to Port 143 from the outside works fine as well.

It's not a firewall Problem, since port 993 and 143 are open, the config files have been checked over and over for 2 weeks and are good as well.

Dovecot log says:
imap-login: Apr 20 13:26:05 Warning: SSL_read() syscall failed: Connection timed out [83.104.224.142]

Doing uber verbose output doesn't bring up any extended information, syslog stays clean as well.
The Problem is not directly reproducable by a certain action, it just arises from time to time. There can be 3 working days without problems, or 6 timeouts > 20 minutes within one day.

System is Debian Sarge unstable with a custom 2.6.10 Kernel.
During the timeouts, mail is still received and put into the users mailboxes by exim, it's just that you cannot access the imap server for approx 20 minutes.

Dovecot version is 0.99.14

Regards
Alexander Heuer