Hey all,

I'm looking for some advice on how best to get a Postfix server set up for sending mail out for a couple of domains.

First, this system is used only as an outgoing mail server. It's not a final destination for anything, and no mail is ever received by it. All replies are received on a different server.

The system is already functioning for 1 domain. Reverse records are set, and mail is being delivered normally.

What I'd like to do is set up a second entirely separate domain within Postfix if possible to send mail through. Using a 2nd NIC, I'd need to force email for this second domain to go through the 2nd NIC so I could properly set up the DNS records for the IP.

I've been going through the Postfix documentation, but thus far have been unable to find anything about having a second domain's email be sent through a specific interface.

I'm also not sure how to go about setting up the mydomain setting in the Postfix config for multiple domains. Again, the reading I've done so far has concentrated more on the server being a final destination for multiple domains, not a simple transit server to send mail out from multiple domains.

The server in question is running CentOS 5 and is fully upadated. If more info is needed, please let me know. Once I know where to look I should be able to figure things out from there.

Thanks.

I think you want to set up virtual domains on your Postfix server. There is a VIRTUAL_README file that comes with the distribution that more or less says how to do that, and what options you have. This will not automatically force mail for domain2 to leave via the second NIC, but it will leave (by whatever path the routing table says to use for a particular destination), so it will get delivered.

I think that Postfix is at the wrong level of the TCP/IP stack to try to force an override of the normal IP routing. You should do that by setting routes properly. Unfortunately, you can only specify one default route on a given machine, without doing some fairly bizarre things. Probably the cleanest way I can think of to make this happen (if you *really* want it to happen) is to run two virtual machines, and set up Postfix for one domain on one, and for the other domain on the other. Then you could have two different default routes.

HTH

Maybe multiple instances of postfix will do what you want. Have a look at

http://advosys.ca/papers/postfix-instance.html