Questions

Q1 Why did I receive a "returned" email that I didn't send?
Q2 Can I avoid worms and viruses?

Answers

Q1: Why did I receive a "returned" email that I didn't send?

Many email worms, a.k.a. "viruses," will send themselves to new targets and forge their return address. If it then bounces, it will be sent to the person who's address was forged.

Let's look at an example. Bob, Mary, and Sue all have email. Bob's computer becomes infected with a worm/virus. That worm will then send itself to Sue and forge Mary's address. Mary's computer was never involved in this process, but it looks like it was. Now Sue receives the worm. This might cause confusion for Sue. Alternatively, Sue's email system might bounce it "back to" Mary and warn her that she has a worm on her computer.

As the example shows, the person with the problem is never aware of it. Everyone else receives confusing email messages.

Q2: Can I avoid worms and viruses?

Our email servers check all incoming messages for known worms. We use many techniques to detect and deal with them. Many of them are rejected before they even enter our email server. Many more are identified and "tagged" when you receive them. This "tagging" is visible in the subject line. If a worm is suspected, the subject line is changed to begin with "*****WORM*****". Unless the sender of those messages tells you that its OK (e.g. over the phone, in person, etc.) you should just delete them.

Unfortunately, sometimes it can take weeks for us to become aware of a new worm and figure out how to detect it without deleting any other email. If you receive odd email that does not have "*****WORM*****" in the subject line, then you should forward it to help@cairodurham.org. With enough samples, we may be able to block it in the future.