Multiple routes/network question...

[cyber7]

Hi Guys, I am almost at the point of installing Zimbra and have a question regarding the server, prior to installing Zimbra.

My environment (CentOS 64BIT):
3 network cards:
(1)Connects to a DIGINET line.
(2)Connects to an ADSL line.
(3)Connects to my LAN.

What I would like to do is route
(1)MAIL TRAFFIC to the DIGINET line
(2)WWW TRAFFIC to the ADSL line
(3)LAN is easy

What would be the best tool to achieve this? The server is built with a FIREWALL, SQUID PROXY (with Rules).

I hope you can help
Kind regards
Aubrey Kloppers
South Africa