[Dovecot] Need a little shadow to MySQL conversion help

Excuse me for being stupid and confused.

I'm trying to convert my dovecot install from passwd-file to mysql. I have a single table called "users" that has 3 fields, user_name, domain_name and password. The data came from passwd/shadow files so it uses the same password encryption as the shadow files do. The directory where the email is stored is calculated elsewhere and not stored in the database. The UID and GID are both mail for all virtual users. The user logs in passing the full email address and the password.

So - what would be the config for using MySQL? Do I even need a userdb? If so - what would it be?

Thanks in advance.