If you want open source antivirus, you can only use ClamAV.
Anyway there are a number of free or commercial antivirus solutions for Linux. (I don't know if any of these supports Thunderbird).

http://www.linux.com/articles/22899

This is a good article about antivirus solutions. You can use ClamAV along with Sylpheed(Claws) because it has integration for it.

Bye, Gyuszk

2008/5/9 Tony Caudel <tony.caudel@gmail.com>:
I am currently using the clamv anti-virus program.  I was wondering if there is a better one for Gentoo, especially one that integrates well with Thunderbird.  That has been my one disappointment with clamav.  Not necessarily clamav's fault since T/B maintains its emails in one long file.

Tony

--
Those who would give up essential Liberty, to purchase a little temporary
Safety, deserve neither Liberty nor Safety.
 -- Benjamin Franklin