> On Nov 30, 2017, at 09:03 , Steve Atkins <[email protected]> wrote: > > >> On Nov 30, 2017, at 1:22 AM, Bjørn Mork <[email protected]> wrote: >> >> "John Levine" <[email protected]> writes: >> >>> Broken rDNS is just broken, since there's approximately no reason ever >>> to send from a host that doesn't know its own name. >> >> rDNS is not a host attribute, and will therefore tell you exactly >> nothing about the host. > > It tells you something about the competence of the operator and > whether the host is intended by the owners to send email. > > Or, for a more empirical way to look at it, there's reasonable correlation > between having missing, generic or incorrect reverse DNS and the host > being a source of unwanted or malicious email.
I’m not so sure about that. Lots of hosts that send unwanted/malicious email have missing, generic, or obviously incorrect rDNS. Lots of hosts that send unwanted/malicious email have valid non-generic possibly correct rDNS. I don’t accept email from the former, but I still get plenty of SPAM from the latter. Unfortunately, until we get widespread deployment of something better than IP reputation based systems, SPAM continues to be a low-cost to the sender side with a high burden on the delivery side and therefore remains a very profitable industry. DKIM certainly could help (though I’m not convinced it’s a 100% effective solution, nor am I particularly convinced we’ve found any particularly effective solutions as yet. Perhaps this is simply the inherent cost of maintaining an open communications infrastructure with a low barrier to entry and the potential for anonymous communications which I believe has value to society and should be preserved. Perhaps someone smarter than I will some day develop a better solution. Owen
