I have modified my delivery agent to deposit files in my Maildir already containing custom flags. For example, x is appended for files that are sent from local users, y is for e-mails from Contacts and z is for e-mails from Whitelisted sources. A file will thus be delivered in the Maildir and be called something like: filename:2,yz Also in the Maildir I created a file called dovecot-keywords and have added these 3 flags in there as so: #cat dovecot-keywords 23 Local 24 InContacts 25 Whitelisted I went ahead and erased all the dovecot-uid* dovecot.index* files but Dovecot won't recognize the flags - furthermore, it labels z as 'unknown-25'! - for both old messages or new messages. Here is a bit of IMAP conversation: a02 select inbox * FLAGS (\Answered \Flagged \Deleted \Seen \Draft unknown-25 Whitelisted ) * OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft unknown-25 Whitelisted \*)] Flags permitted. a03 SEARCH KEYWORD Whitelisted * SEARCH * FLAGS (\Answered \Flagged \Deleted \Seen \Draft unknown-25 Whitelisted Whitelisted) * OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft unknown-25 Whitelisted Whitelisted \*)] Flags permitted. a03 OK Search completed (0.004 secs). a04 SEARCH KEYWORD unknown-25 * SEARCH a04 OK Search completed (0.004 secs). I know for sure there are files with the z letter in their name in the Inbox. What is going wrong ?