Howtoforge posted a guide about setting up Ubuntu Jeos as a spamfilter
>> The Perfect SpamSnake - Ubuntu Jeos 9.10
This tutorial shows how to set up an Ubuntu Jeos based server as a spamfilter in gateway mode. In the end, you will have a SpamSnake gateway which will relay clean emails to your MTA. You will also be able to view your incoming queue, train your SpamSnake and carry out a few more advanced operations via MailWatch.
>> The Perfect SpamSnake - Ubuntu Jeos 9.10