> If the mail server is Listserv Classic on Windows (which handles
> incoming SMTP itself), how do I implement these checks?

You implement them in your MTA's spam filter, as part of a carefully thought-out and comprehensive series of tests aimed at reaching a workable compromise between incoming spam level and level of rejected but entirely legitimate messages. If you were to simply implement the steps suggested in the Wikipedia, you would not be seeing this message (that I am typing right now), because L-Soft has just been added to at least one DNS blacklist. The reason L-Soft has been blacklisted is that one of the LSTSRV-L subscribers felt that the original message from Cris Fuhrman was uninteresting and thus, by that user's definition, spam. That subscriber reported L-Soft anonymously, perhaps by pushing the wrong button in his e-mail client, and we are now blacklisted. This is a "one strike and you're out" universe; I too will blacklist this person for life if I happen to find out who it was (this happens way too often to be worth the research effort), and I will not care whether or not it was a mistake because of a mail client where the "delete spam" button is 3 times the size of the normal "delete" button and it is so easy to push the wrong button. Even if the user apologizes, the "delete spam" button will still be 3 times the size of the normal delete button, and I am going to get blacklisted again, and again, and again. Why take that risk for a free service? With a full-fledged spam filter, you combine and intersect a lot of blacklists and weed out one-off cases like what just happened on this list.

  Eric