Don't always believe what you here.
A well written virus will dessimate any system, regardless.
Take the I Love you virus. It was written for outlook. While it did not destroy outlook, it used a mechanism in outlook to deploy. That same virus, when run in netscape, destroyed netscape to the point that you could not use it.
When deploying *ANY* mail client or gateway, you should employ virus protcetion/scanning software.
My long standing belief is that *ALL* attachments should be scanned/quarrantined/blocked at the mail gateway and not the client side.
There are several products that do this, NAI's groupshield and TredMicro are among the top ones. Norton also has a product, but I still have bitter feelings over norton andtheir aol style of octopi installations.
In any event, what ever you choose, make sure you get AV software with it and configure it for extenstion blocking.
What is extension blocking? It is the ability to block file extensions instead of just viruses. So if the latest and greatest .vbs virus is released and you have your gateway configured to block all .vbs extenstions, then it will not infect your netwk.
For a list of what I preach to block:
www.directionweb.com/nettools/extensions.txt