[Dovecot] Public mailboxes with ACL in 1.2

Hi,

I'm new to Dovecot 1.2 and I'd like to replace uw-imap.

I'd like to have the following setup:

• Personal mailboxes using maildir for all users (no problem)
• Public mailboxes for certain people who are in special groups from /etc/group localed in /var/spool/public as a maildir with subfolders for each group (which should only be visible for that group and also secured by filesystem group permissions). At best those folders should be visible for the users below "shared"-folder or parallel to the inbox.

The public mailboxes should be secured by custom ACLs (so that not all ppl. can create new folders and so on).

How can I make Dovecot authenticate against pam and use groups in /etc/group?

When I activate the ACL plugin all public or shared mailboxes are hidden. How can I avoid this for the public mailboxes?

Thanks in advance. Sven