[Dovecot] Restricting access to imap ?

[Jakob Curdes]

Is there a way to restrict access to imap on a per-user basis ? 
Situation is as following : internal server w/many users, some users 
work also from home. I would like to make their mailboxes accessible 
from outside via imaps, but only for selected users with strong 
passwords. If dovecot would run via inetd, I could use hosts.allow 
patterns for this. Any idea or is this just not possible ? (I know the 
easiest way would be to connect via VPN but thst is not possible at the 
moment).

Yours,
Jakob Curdes