Incoming email (postfix) trouble

Hey! I just setup a virtualmin server and love it so far.

The only oroblem I'm having isn't the server will not accept any incoming email whatsoever. It replies back to the sender with the following message. I have made sure that mail is enabled on the domains, that the accounts in question have been created and can be accessed via webmail. These accounts are also able to send mail. The server has a FQDM and I've checked that the domain mapping lookup tables setting is set to hash:/etc/postfix/virtual

What am I missing?

This is the mail system at host latte.quacktacular.net.
 
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
 
For further assistance, please send mail to postmaster.
 
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
 
The mail system
 
<":fail:"@quacktacular.net> (expanded from <the@debrin.ca>): User unknown in
   virtual alias table