[Dovecot] Fully virtualized w/ postfix?

Hi folks,

I've poked through the archives and google and have not seen how do do this. Is it possible to virtualize ALL emails on a system? That is, I want delivery only to e.g. /var/mail/vmail/domain.tld/user/Maildir/, and for authentication & userdb to:

1. Try /etc/passwd, and if someone is there, automatically append the "default" domain, otherwise,
2. Authenticate off a mysql db or similar.

Is this kind of "fallthrough" user lookup and auth. possible with dovecot? I assume the delivery can probably be done by just telling postfix to use dovecot as the local delivery agent.

Thanks for your help!

--JB