Bouncing mail for invalid users

One way to solve this is to use the virtusertable to only accept mail for the specific valid users and reject mail for anyone else.

First list the valid users:


Don't forget postmaster and abuse (which should go to you)

      postmaster@virt.dom    postmaster
      abuse@virt.dom         abuse

And then finally have a default entry which calls the error mailer:

      @virt.dom              error:5.1.1:"550 A-ha, you loose"

This last entry will reject mail to any address other than the 5 listed address.