He is sending emails spoofing one member and copies the email to others on the list. Some of the addresses are apparently old ones and now invalid, and the sent message bounces back to the member he is spoofing as undeliverable.

At least that's what I'm seeing, as I'm getting the bounced copies back in my mailbox.

I don't think we can do anything about it other than not opening them, deleting them, and waiting for him to get tired of the game. This started about 8-10 days ago.