Yep. They use slavery. They just revealed it. Read by yourself:

" Ballmer said only about 10 junk e-mails make it through to his inbox each day because of Microsoft's anti-spam technology. "

And then

" "Literally there's a whole department almost that takes care of it," he said. "

Yes, the best anti-spam technology is a human clicking on JUNK or NOT JUNK for each email. Reminds me of "Asterix légionnaire""Le Bouclier Arverne" when the roman entrepreneur talks into a horn attached to his desk saying "Call the security, now", and then a small slave hidden in the desk under that horn opens a door and starts running to deliver the message...