Security software choices & recommendations

[baronne]

Hi,

I am looking into setting up an Ubuntu server. I'm keen to look into the various products available for:
Spam protection
Internet filtering / proxy
Mail Server

What software is out there, I've heard of a few here and there such as SpamAssasin and DansGuardian.
I'd be grateful to hear your thoughts & recommendations of the stuff that's available.

Cheers
Baronne