Yahoo, GMail, AOL (and perhaps a few other providers) have "feedback loops" with the big email service providers that allows them to see who is marking what mes

Yahoo, GMail, AOL (and perhaps a few other providers) have "feedback loops" with the big email service providers that allows them to see who is marking what messages as spam. Mailchimp in particular is pretty aggressive about terminating your account if too many people mark you as spam.