score low on spam setups.
They use them to check the messages they send and adjust them to be "good" messages all the time.
They are using a myriad of techniques, even I get about 8-10 messages a day, in my inbox that are SPAM.
Though I also get about 200 that are moved directly to my SPAM-Box... for review.
I have been getting about 10 valid messages a day now that I have unsubscribed from most mailing lists.