[Dovecot] which architecture to use?

[GVG GVG]

Dear List,

Based on the following installed environment:

- OpenBSD (latest version!)
- PostgreSQL
- dovecot with SSL

would like to have a mail server which accepts system as well as virtual
users and being able to connect to their mailboxes either via an MUA
(Thunderbird etc.) or a web interface (squirrel mail?).

When using the web interface, non registered users should be able to creat
e-mail accounts which will be dovecot virtual users!

Which components should I use?

Thanks