It looks like it might be something generated by one of those
spam viruses.  Probably snarfed the addresses from posts stored
on someone's local PC.  I've had hundreds of "non delivery"
messages from email servers and norton or mcafee NT virus
scanning server software, that posts from my email address or my
domain name were undeliverable --- messages that were forged
emails sent to every email address the virus could find on the
computer's hard drive.

I hope that everyone posting regularly to this group has decent
virus protection, and that you update it daily.  I've got
Postini/McAfee at my ISP's mail server, and Norton on every
Windoze machine on the net (don't need it for the Linux boxes).