I am trying to design a dual isp internet connection using a 1841 router with 2 t1 wic cards going to 1 pix with a failover pix. the goal is to route email out an existing isp connection and move all other traffic to new isp connection.
AFAIK you can make use of route-maps in which you match the outgoing traffic's port number related to mail using an acceess-list and mention the next hop to be taken for the same.
you can refer these links for more info on configuring up the same..
