Why do I receive undeliverable notices for messages that I never sent, and from people I don't know?

If you receive UNDELIVERABLE NOTICES about emails you did not send, you are the victim of "Email Spoofing." Email spoofing is when email appears to have been sent out from one source was actually sent from another source. In essence, your email address was forged. Although you did not send the message, it was sent from another computer that has your email address in it.

Most undeliverable emails are sent by computers infected with email-type viruses. These viruses infect computers that do not have proper up-to-date virus protection. Once the computer is infected, these viruses scan the Address Book, Inbox, and other areas of the infected machine gathering email addresses. After gathering email addresses, the virus generates virus-infected emails, randomly putting the harvested addresses that it found during its scan into both the TO: and FROM: fields of bogus emails. The emails usually contain a copy of the virus disguised as an attachment. These viruses act as an email server, that is, they send these emails out when the infected computer is online. These email viruses are smart enough not to use the actual email address of the infected computer.

It is very likely that someone who has your email address on their computer got an email-spoofing virus which placed your email address into the FROM field of the bogus email. If the email is rejected by the receiving email server, (either because it contained a virus or the email address no longer exists) an UNDELIVERABLE NOTICE is sent back to your email address rather than to the computer from which it originated.

There are many viruses that work in this fashion, some of which are extremely active at this time. The industry is working on new methods to reduce this problem. Until then, it's best to simply delete them from your Inbox.