> Incidentally, although it may still be the conventional > wisdom in the IETF that DNSBLs don't work and aren't useful, > in the outside world where 95% or more of mail is spam, > they're essential tools to run a mail server. Although there > are indeed lots of stupid DNSBLs, those aren't the ones that > people use, and there are widely used ones that have > vanishingly low false positive rates that let you knock out > most of the spam cheaply so you can afford to do more > expensive filtering on what's left. Spamhaus estimates, > based on the systems that pay for their data feeds, that > there are about 1.4 billion mailboxes whose mail is filtered > using their lists, and they're the biggest but hardly the > only popular high quality DNSBL. It's pretty clear that > there are a lot more mail systems that do use DNSBLs than don't. As an operator of a large mail domain, I'd like to reiterate John's comments above. DNSBLs work, are very cost (and computationally) effective, and are in widespread use. Regards Jason _______________________________________________ Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf