[Dovecot] user_db, uid/gid and maildir

Im experimenting with putting all my virtual users mail under 1 directory with belonging to a system user created for the purpose. The mode on the directory (and subdirectories) is 770.

I keep all my virtual users details in a postgres database.

My interpretation of the wiki documentation is that if the user_db query returns a uid column and a gid column containing the numeric uid and gid of the owner of the directory, then dovecot should have no problem using mail in these folders. Is that correct?

(I'm actually getting permission errors appear in the log file on the directories when I try and attach with a client, which reports "Cannot get LIST information for pattern `*' on IMAP server a.b.com unknown".)

thanks Glenn