What are mailing lists and how do I join one?

I read this article by this guy who said he got $15000 in between 20-50 days by sending six letters out with a dollar in each of them with this list or whatever with these six people on it or something and I add my name to the list and soon I will have tons of cash coming in through the mail and it's perfectly legal because it is a service and you are paying willing participants. It also said something about posting the message on online message boards.