Routing Data out of Specific interface help!

Guys,

I'm using the community (free) edition of untangle. I have a single WAN connection but I have 3-4 external IP addresses.

Can someone provide some guidance on how I could route specific traffic (Say from a host, or based on port / protocol) out of a specific external IP address as opposed to the default external?

I have some services that for security purposes I would like to distribute behind different IP addresses. i.e. I'd like my mail communication to go through a specific external ip, http another, ssh another, etc.

Thanks in advance.

-dt0x