How do I setup postfix as a null client for two domains on the same host? I currently have postifx setup as a null client for one of the domains (complete with SPF records). How do I add one more domain to the setup? And after adding the domain, how do I make PHP mail() send out email appropriately from the corresponding domains/IP addresses?
P.S.: I have two IP addresses at my disposal, one of which I use for the first domain.