You'll notice in the admin interface there's only 1 way to add in source to feed. To get email to go out of the right virtual mta use the pattern-list directive. <pattern-list vmta> mail-from /domain1.com/ virtual-mta=virtualmta1 mail-from /domain2.com/ virtual-mta=virtualmta2 </pattern-list> in your source directive add: pattern-list vmta Yes, I realize this is nothing revolutionary, but it might help out a newbie.
