Courier IMAP: inbox empty after upgrade to lenny
After upgrading my mail server (mail.nobaq.net) from Debian etch to Debian lenny, all IMAP inboxes were empty (IMAP server: courier/SSL). Even the list for subscribed folders in Thunderbird was empty.
After a long time I found the solution: The new version of courier seems to require the Maildir directory to be owned by the specific user. Furthermore, the group must be set to the primary group of the user (in my case "users"). All other permissions seem to be ignored.