Weird email messages with "re:movie" and "re:application" in the subject line..

And I've gotten bounces from mail allegedly from me. It's not L3's
fault; this particular worm forges From: lines on its email.

Another day, another worm.

    --Steve Bellovin, (me) (2nd edition of "Firewalls" book)

fault is debatable. Because forgeries are now so common, particularly in worms, why would you send these notifications to anyone other than the recipient? Let the human decide if the right thing to do is notify the sender.