Originally Posted by kshazad86
My imap server and ftp server recently went down, this is the error message:
Any ideas how I can investigate the root cause?
Dovecot is known to have some issues with crashing or failing to respond due to issues related to the internal clock of the server being changed via syncing. You should try swapping to Courier.
If IMAP still continues to fail most likely your server is reaching its maximum IMAP connection limit quite a few times. In turn this will cause chkservd to restart the service, as it could not connect.
At this point you would want to raise this limit in WHM -> Service Configuration -> Mailserver Configuration -> Maximum IMAP Connections (Total). I believe increasing the IMAP Connections limit to 100 would be more than sufficient and solve your problems in addition to swapping Dovecot for Courier.
You should also note, switching mail servers may cause some mail clients to re-download all stored mail messages for their account. This is primarily seen with POP3 configured accounts.
Hopefully this solves your problem.