[Dovecot] Detecting unused accounts

I'm looking for a way to figure out which accounts have not been logged in to in over n days. It occurs to me that, perhaps, the way to do this would be to look at the mtime on one of the dovecot-maintained files, like 'dovecot-uidlist'. Is there a particular file that would be modified on (almost) every login, whether it be via POP or IMAP?

-Ben

-- Ben Beuchler There is no spoon. insyte@emt-p.org -- The Matrix