>This is only partly true. Technologically the solution is difficult, but it's easy from the social side as carriers can blacklist the smaller carriers that all

>This is only partly true. Technologically the solution is difficult, but it's easy from the social side as carriers can blacklist the smaller carriers that allow this fraud to take place. So, the MAPS RBL (and most of the following dns-based blacklists) did this for spam; and it helped a lot - I mean, I think it's the primary reason that ISPs don't actively serve spammers (spammers as defined by the RBL) On the other hand, it didn't solve the problem; if your mailbox isn't behind serious spamfilters, an address that has been on the internet for any period of time still gets hundreds of spam mails a day.