Deb,
There is a particular feature of e-mail worms such as Netsky, Mydoom, Sobig.f and Bagel which could cause some inconvenience.
Basically these worms have the potential to spoof an e-mail address - that means to make it look like it has originated from somebody / somewhere else. There will be other people who have had their machines infected by an e-mail worm.
If they have your address in their contacts list, the worm may try to send itself to that address AND send a mail elsewhere purporting to originate from your address.
If the message is then detected as a virus and bounced by the intended recipient's mail system, an error message will be generated and sent to your address, and you will not be sure of what is happening.
These worms victimize innocent bystanders by sending out its worm email with fake From addresses. The worm searches through the real infected person's hard drive, sifting through their files looking for email addresses. It then composes its email using the found addresses in both the From and To lines of the email.
Ironically, the one person whose name never seems to appear in the From field is the actual person who is infected and whose machine is spurting out this malicious spam worm.
In essence, those who never become infected by the worm are the real victims and often have to contend with other angry recipients who don't understand the forging technique and accuse them of being the sender. And if the worm's volume weren't enough, the innocent also receive the out of office replies, undeliverable messages, and virus alerts.
These return message notifications cause additional stress for everyone except the infected person who remains blissfully unaware of the scourge to which they are subjecting their friends, families, and colleagues.
I hope this helps.