Hello

We have a server on which we run multiple instances of dovecot. Each instance serving a domain and binding to a specific IP. The whole thing on three servers using the proxy ability and replication of dovecot.

Now one domain has more users and we start seeing very strange behaviour.

As soon as about 45 users have connected to the imap service ip of that instance, the server accepts the connections and then disconnects without showing the IMAP banner. This happens on all of our three servers and only for that specific domain (which has most connections).

While this occurs, there is no problem with the other instances for other domains on the same physical machine. So the database backend etc. are not the issue.

While this occurs, there is no hint of what goes wrong in the logfiles. I did even set mail_debug=yes but that still does not produce any output of why clients get disconnected prior to the server displaying the banner.

Any hints on where I could start looking for the error, or get more debug output as with mail_debug=yes ?

-Benoit-