We're currently running a 3-legged firewall under ISA 2004. The external NIC of the server is assigned to approximately a dozen IP addresses but traffic emanating from our internal network always appears to come from the principle IP address assigned to that interface. I am trying to figure out how to force specific traffic (in this case, outbound SMTP) to appear to be from a different address (i.e. one of the OTHER 11) when it leaves... I can't seem to get an outbound rule to allow me to designate the "apparent" source address.