I have received SPAM before which appeared to have been sent to me by me (one of my e-mail addresses was listed as the sender e-mail address.) Due to the number of spam e-mails Don is getting everyday, I'm thinking that he is getting SPAMMED by a spam-bot or a mass mailing worm which plucks e-mail addresses off of webpages, out of address books, or from anywhere really and then sends e-mail using that spoofed e-mail address.
Cheers!
Bill