Apparently Apple think you can just bounce stuff to spammers:
5. Delivering a One-Two Punch to Spammers
Yes, Mac OS X Mail can help you deliver a staggering blow to
spammers. Simply pull down the Mail menu, choose Junk Mail, and
select Automatic. The next time you receive email, Mail will
move suspect email into a Junk folder.
Now you're ready to deliver a real knockout punch to spammers
by taking advantage of yet another potent spam-fighting weapon:
1. Click on the Junk folder.
2. Type Command-a to select all of the email in the Junk folder.
3. Choose "Bounce to Sender" from the Message menu.
Mail will return the selected messages to the senders marked
"User unknown," making them think your email address invalid,
encouraging them to drop you from their lists, and, thus,
eliminating spam at its source.
Someone really aught to make them publish a retraction of this. People being joe-jobbed get enough bounces from invalid addresses as it is, never mind people bouncing because of their filters.
(I didn't receive this - I'm just re-posting something I saw on a list).