How do i forward outgoing traffic for specific port from internal network to specific external ip in watchguard? I know how to forward incoming traffic using SNAT.
While I'm not familiar with Watchguard products, the concept of static NAT should work for both inbound and outbound traffic.
Researching it a little, it appears:
You would configure it using "1 to 1" NAT it appears (Watchguard's terminology for static NAT I guess).
See OPTION #2 in that link from Watchguard.
(Oops...I misread your post. Are you wanting only specific outbound ports to be expressed as a certain external IP or all ports from one IP. My example is all ports from one internal IP. The example PDF should still help you. You should be able to use Dynamic NAT and a policy to allow for instance outbound port 25 from an internal IP to use one external IP and the rest of the ports (as a policy below the port 25 policy) to use a different external IP)