I was wondering if there was a PAM module, or some kind of software that could translate a username@domain.com logging into a dovecot IMAP server, into a linux user account by reading the /etc/postfix/virtual file for virtual mappings that to the user account. My virtual file might look like this:

user1@testdomain.com localuser
user10@otherdomain.com localuser

I would like to enter the credentials "user1@testdomain.com" or "user10@otherdomain.com" in my webmail client, have it pass the credentials to dovecot, and finally parse the virtual file for matches to the "localuser" linux system account. Then the login process would login the "localuser" linux system account and let the webmail user see mail from the user's maildir.

Is this even possible?

Thanks in advance.

you will probably have to parse the name and look it up manually, but it's possible that something like this exists. either way it should be fairly simple, providing you have access to the "table" with the addresses and local user names.