That's funny. With this recent mydoom virus I got a lot of "I think your email server is infected with a virus" messgages. I like being able to tell them it does not effect our stable linux servers, only fragile windows PCs.
I also had a client a while back who actually left because she the email server was rejected a .url attachment. She thought we were accusing her of sending viruses. I told her to simply post the url in the body of the email or if it was another type of attachment zip it up like the error messages states. She flew off the lid and lucky for me left.
"This message has been rejected because it has
a potentially executable attachment "Compare Prices and Read Reviews on Gotcha!: Swindles, Scams, Cons & Rip-Offs.url"
This form of attachment has been used by
recent viruses or other malware.
If you meant to send this file then please
package it up as a zip file and resend it."