[Dovecot] Tracking logins

Hi,

I'm using dovecot-2.1.17 on fc18 and wondered if there is some mechanism, perhaps a database, that can store the logins/logouts for each user? I realize there's something already logged to syslog, but I'd like more of a history.

While lastlog is great for users that actually login, my dovecot users don't login, just check email via pop and imap.

Any ideas greatly appreciated. Thanks, Alex