They blew it
         

<p>If you're a business with a mailing list that may be of questionable quality, there are three possible options open to you. One is to err on the safe side, dump the whole list and start over using known best practices for list building. This is commendably cautious, but sometimes hard to justify to the marketing department. Another is to ignore your doubts and just keep sending to the whole list anyway: this is the kind of thing that gets you into spam blacklists. The third option is to do what's called a permission pass, which is to send a brief message to all the addresses on your list asking if they want to remain on it. The message should contain no advertising copy (to reduce the risk of it being seen as a kind of surreptitious spam) and the default should be to unsubscribe: in other words, if someone doesn't write back and say <q>'Yes! Keep me on your list!'</q>, you should drop their mail address. A permission pass is a gray area &mdash; it's a tacit admission that you've done things the wrong way in the past, but also a declaration that you want to start doing them the right way. Permission pass mails should be a last resort, but they shouldn't be viewed as spam.</p>
         

http://www.spamnation.info/blog/archives/2010/04/they-blew-it.html