Hopefully this is a simple question, seems easy enough. Basically I'm just
wondering how to setup either outbound NAT or 1:1 NAT to solve a problem I
am having, and neither seem to be documented yet.

My m0n0wall's WAN ip is dynamic, and I have 2 static ips assigned to it
via Server NAT and Proxy ARP. I am using regular NAT rules to forward all
the traffic to the correct servers.

One of the severs behind m0n0 is a mail server, and when it sends mail it
goes out via the WAN (dynamic) ip. This is bad because dynamic ips are
automatically blacklisted on some RBLs.

I'm just looking for the easiest solution to route some or all outbound
traffic out over one of the Static ips, without interfering with my
existing configuration too much.

The end result I'm looking for is for all TCP packets on port 25 from
192.168.0.115 on the LAN to go out via one of the two static ips.

If there is a way to make a outbound rule for that, it would be ideal.

Or perhaps I should be using 1:1 instead of server NAT ?

Thanks a bunch, your suggestions are greatly appreciated.

Josh