What would happen if mail2.foo.com used mail.foo.com as an outbound MTA? Then mail to foo.com would be captured and mail not to foo.com would be sent on its merry way. Wouldn't it?
I use Postini as an inbound and outbound MTA on my single server and it works great.
In the WebAdmin interface choose Servers>mail2.foo.com>MTA. Look for "Relay MTA for external delivery" point that to mail.foo.com. Choose Servers>mail.foo.com>MTA. Look for "MTA Trusted Networks". Put the IP of mail2.foo.bar in it, along with the other IPs that should also be there.
If my thinking is correct the your mail should flow. It's not quite the same as what I've done, so your mileage may vary. Good luck. |