Return Delivery of Mail I've never Sent

[Bob Perry]

Just setup mutt and I've begun to notice mail return to me 
indicating that it did not pass the server content filter, 
etc.  The last one stated that a virus was found, file name 
disco.zip, virus name W32/Netsky.c at MM!zip and apprarently 
was found by McAfee Scanning Engine (4359/4.3.20).  What 
makes it worse is that the recipient is not recognizable.

I understand that my system can be used as a mail relay and 
would like to know how to combat this.  Can anyone point me 
in the right direction so that I can quickly resolve this 
issue?

Thanks,
Bob Perry

-- 
I've learned that whatever hits the fan will not be evenly
distributed.

FreeBSD 4.9-RELEASE-p2 #0