Postfix/Dovecot Issue

I am having a problem with my Postmfix > Dovecot installation. I have used webmin to administer with mostly defaults. The problem I am having is this:

When I migrated their old cpanel backups, it put all their waiting mail in a file called /var/mail/username@domain.com

Dovecot is working fine with this, I can access webmail and also pop mail from this box.

However, postfix is delivering all new mail to a file called /var/mail/username-domain.com. Thus its not getting received by the users.

In virtual domains under the postfix configuration in webmin, I can see the translation of username@domain.com –---> username-domain.com but if I try to edit this to username@domain.com---->username@domain.com or just delete this mapping period, postfix bounces the mail back to sender with "username" is not on this server.

Thanks for any help in advance,

Justin