[Dovecot] Problems with Mozilla

Hello,

I've some problems with Dovecot and Mozilla. First of all i have to mention, that Dovecot is installed on SuSE Linux 8.2 and uses up to 20 Win32 Mozilla clients. If you need further information, please let me know.

My problem is, that I got one or two times a week a login failure from Mozilla, and the clients can't connect anymore. The error message from Mozilla after a long time "checking server capabilities" is "server is not an imap4 server". I haven't found something usable in the logs except for a login timeout of the clients who want to connect. If i kill the imap and imap-login tasks and restart redove, everything works well for some days. Is there anyone who knows something about my problem?

regards Tres!