>> Postfix expects an empty set (i.e. no rows returned) if it is to respond
>> negatively that a virtual alias does not exist. >> Returning NULL does not equal no rows returned. > > email builder: >> Are you sure?? > > 100% confirmed. To return NOTFOUND, you MUST return NO RESULT. So with NULL, Postfix must be trying to do something, like what, map and deliver to n...@example.com and failing? Because I'm finding the same result when returning NULL (rejected after RCPT TO with "Recipient address rejected: User unknown") In any case, this is helpful to know so I can adjust my query appropriately.