I've successful got our new postfix server up and running with approx 200 domains on it. Using virtual IPs on a single interface, i have approx 20 IPs listening for mail. However, I've run into a potential problem.

Is there a way to get smtp traffic to go out an IP based on the domain? I have the /etc/hosts all set up with the domains. I also have the users using the correct IPs when they connect to us for their outgoing mail, but it appears all traffic is going out over the first IP address on the interface.

So I'd like to be able to say....

DomainA
mail.domainA.com
pop & smtp use: 208.100.100.1

DomainB
mail.domainB.com
pop & smtp use: 208.100.100.2