We are having issues with our Postfix. The POP and IMAP services randomly stops working an sent e-mails return a "Command time limit exceeded".

We've found out that running these command fix the problem:

service cyrus-imapd stop
rm /var/lib/imap/tls_sessions.db*
rm /var/lib/imap/deliver.db*
rm /var/lib/imap/db/*
service cyrus-imapd start
service saslauthd restart
But then, minutes after, the issue comes again. We are running these commands repeatedly but we need to fix this issue.

Any clue?