Upgrade to 3.1 broke Dovecot configuration
Today I upgraded my server from 3.0.5 to 3.1.5. It went mostly fine, but all mailboxes were empty after the upgrade. New mails would come in though. Upon further inspection, it turned out that previously, mail was stored to
/var/vmail/mydomain.com/myuser/{cur,new,.Subfolder}
while after the upgrade, mails were being stored in
/var/vmail/mydomain.com/myuser/Maildir/{cur,new,.Subfolder}
I coulnd't quite make up in the configuration files what caused this difference (But it seemed to occur from the maildir location being stored in the database?), but I ended up moving all mails into the Maildir subdirectory. A lot of work for dozens of e-mail accounts.
Any clue what could've caused this?