Originally Posted by till
Check that the settings under System > server config > mail are correct. especially the imap server type and the filter language must match the software installed on your server.
For sure they're set to the correct things but it is possible that the courier-maildrop package wasn't installed at the very beginning. It has been for a few weeks already now. Is there configuration I need to edit?
EDIT: Although the package maildrop was installed since the beginning. By the looks of it this is the package that is needed so I just removed the courier-maildrop package. Still not working though...