Filtering SPAM with Linux

[<ivan.hernandez () globalsis com ar>]

Hello. I have a box with linux that is acting as NAT and Firewall (also
cache with squid and reverse proxy with pound).
I have an internal MS Exchange server that goes to internet via NAT, and
i dont have any chance of removing it, but i would like to filter the
incoming traffic to remove spam.
My net looks something like this:


INTERNET <---> x.x.x.x LINUX BOX 10.1.20.100 <---> 10.1.20.1 MS Exchange

What can i use in the linux box? I have found things like MessageWall and
so, but i need better recomendations from people that already doed it.

Thanks!!
Ivan Hernandez

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