Chuck; The way I understand it, the undeliverable messages are being returned to me because whomever has my email address in their now-infected computer address book, has adopted my email address as the sender.

So if the infected email with my email address as the "sender" is sent to someone with anti-virus protection software, it is being returned to me as "undeliverable" as if I sent it ... which I did not.

If someone else's address book is invaded by the worm and adopts YOUR name as the sender to all the address in that address book, YOU will be receiving the same type notifications that I am from infected undeliverable mail.

This is why many of the email addresses that are being returned to me as undeliverable are not known to me ... because they are stored in someone else's address book who has the virus. But the emails that ARE being delivered with my email address as the return address, were not sent by me. It was sent by the worm in the infected computer.