Re: Requiring PTR

Hector Santos wrote:
> Many systems, and naively believed AOL too, I believe used services 
> like from MAPS RBL which lookup the zone owner to determine if this 
> was a home or business tier.
They do -- or rather, dynamic vs. static. If you're in the MAPS dynamic 
IP range, you won't even get a TCP connection; you'll be blocked at the 
firewall.
> Its stupid I think and x821 always allowed PTR checking as an option, 
> but it was so unreliable, it wasn't a real issue and hardly used in my 
> experience. 
AOL has been checking for a valid PTR for at least five years. It was 
their judgment that a lack of PTR record was a reliable indicator of a 
spam source. They also experimented with verifying that the PTR and the 
forward A record match, but that got way too many false positives.
FWIW, I ran a bunch of tests using our traps and a pretty good spam/ham 
corpus at Habeas, and reached the same conclusion.
<csg>