Issue: A user is unable to access their email, instead they receive a message as the example below:
Unexpected condition from IMAP server, closed or corrupt connection to IMAP. Possible mailbox corruption.
Often this is the result of a corrupt dovecot.index file.
Server logs located at /var/log/maillog will likely display lines such as the below:
dovecot: pop3(email@example.com): Warning: fscking index file /home/username/mail/domain.com/username/dovecot.index
Users of Microsoft Outlook will see errors that reference: Outlook Error 0x8004210A
Solution: Remove the file so that it is automatically recreated.
SSH into server.
Search for dovecot.index
mv dovecot.index dovecot.index-corrupt
Log back into email and the index file will be recreated.