I have solved the issue. However it was not an Horde/IMP issue. I just missed one step in the migration process from Courier-IMAP to dovecot. Actually I didn't renamed the Courier-IMAP subscription file to dovecot's *subscriptions* file. More details at: http://wiki.dovecot.org/Migration#head-4f3425222ecde743f302d5c276e80a365a8b487c http://wiki.dovecot.org/Migration