[Dovecot] Problems finding information on passwd-file

I've recently converted over to dovecot to uw-imap, and am having a

heck of a time trying to find actual docs that describe how to set up virtual users properly without using ldap or posgres.. Basically I need to know what goes in auth_userdb and auth_passdb for a system with *NO* local user accounts in /etc/passwd and /etc/shadow. I will only create mbox files for these users in /var/mail/%u and alternately a home directory where they can store their own mail folders under /home/%u.

How can I do this, given the current dovecot codebase? I've googled

for a few hours, talked to many people on irc, and checked the mailing lists (of what I could find) related to this, and found nothing whatsoever describing how to achive this. Dovecot apparently supports "virtual users", but I can't find any supporting documentation that describes exactly HOW to set that up.

Thanks in advance.

d.