I am trying to get postfix to send outgoing mail on a specific interface / IP address. I can find lots of info on how to set the outgoing domain, but that is working fine.

Our system hosts 2 domains, dqzone.com on 72.18.192.214 and dqsoft.com on 72.18.192.215. When I send mail using postfix -f it uses the first interface available which is the 214 address. Unfortunately, I want outgoing mail to all be from dqsoft.com which uses the 215 address, not the default 214 address.

Since the reverse IP lookup for 214 is not dqsoft.com, this causes us to get flagged by some spam programs causing delivery issues.

I have searched the docs and can find a mydomainname= directive for main.cf, but the only interface information I can find is for proxy server stuff which is not what I need.

To clarify, an email header from something I send currently shows:

I want it to show:

Blitzkrieg ('tanks in advance!)
Christopher

you need to explain your network topology really. if you're doing things correctly, then this is nothing to do with postfix or the server it is running on, it's down to your internet edge device - hopefully a firewall, where these IP addresses live. if for some unholy reason those internet ip's are on the server themselves [shudder] then you should be able to do some postrouting natting on the box with iptables without too much trouble.

Both 214 and 215 IPs are both on the same server. It looks like this:

eth0 Ethernet 72.18.192.214 255.255.255.0
eth0:1 Ethernet (Virtual) 72.18.192.215 255.255.255.0

I suppose I could swap the IPs on the virtual and default, but that scares me a bit when all I really need is for the outgoing mail to go out on 215 instead of 214? I know we have some other custom servers that run on 214 that I would then have to reconfigure to listen on 215 instead...

Are you saying ALL outbound traffic is from 214 since 215 is only a virtual port and it is impossible to get mails to show as coming from 215 instead of 214?