Dovecot problems after change from courier to dovecot


Active Member
Jan 24, 2009
cPanel Access Level
Root Administrator
Recently all our servers had automatic change from courier to dovecot. After this we have been receiving lot of problem reports from our customers. We are still trying to pinpoint the exact problem and we are open to any ideas from you. However the increase in email related problems reported after the change has been over 10 fold thus it has to have something to do with dovecot configuration or the change it self.

Following problems / errors have been reported:
  • cPanel RoundCube: Unexpected condition from IMAP server, closed or corrupt connection to IMAP. Possible mailboxcorruption.
  • cPanel RoundCube: An error occurred! Server error! (OK).
  • Outlook: Synchronizing subscribed folders for [email protected].' reported error (0x800CCCC0E) : 'Outlook cannot synchronize subscribed folders for [email protected]. Error: Cannot connect to the server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).
  • Outlook: Sending and receiving reported error "0x80004005" : The operation failed.
  • Outlook: Emails stuck in the send folder. May be due to the above errors.
  • Outlook: Duplicate emails received to Outlook when using POP3. However no duplicate emails in the server nor any forwarders etc that could make up duplicates.
The cPanel RoundCube "Unexpected condition from IMAP server, closed or corrupt connection to IMAP. Possible mailboxcorruption." error has been the most usual error and we got around hundred of these reports from customers within few days after the change.

Any ideas? What kind of dovecot configuration is suggested in large systems?

Also I have to state that with courier we had very little problems. The courier was really robust.


Staff member
Apr 11, 2011
Hello :)

It's possible these are separate issues, so it's a good idea to investigate each problem individually. First, do you notice any specific entries in /var/log/maillog or /var/log/exim_mainlog when receiving the error messages in Outlook?

Thank you.