In <40db7c8d(_dot_)32154(_at_)achurch(_dot_)org> achurch(_at_)achurch(_dot_)org
(Andrew Church) writes:
I am not aware of a difficulty in setting up a PTR record for an IP
address that runs a mail server. We never said it had to equal the
forward DNS or anything else. We just require rDNS and a valid one at that.
Then you must have had a nice provider. When I had an 8-IP block, I
had a hell of a time (and was ultimately unsuccessful in) trying to get my
ISP to either delegate reverse DNS to me or do rDNS for me. I've since
downgraded to 1 (static) IP, and now I at least have rDNS, though according
to SORBS it "looks like a dynamic dialup address" and the ISP won't let me
change it.
May people are under the misunderstanding that you can't delegate
anything smaller than a class C (aka a /24). You can, but it does
require playing some tricks with DNS. See RFC2317 for details:
http://www.ietf.org/rfc/rfc2317.txt?number=2317
There is a chance that your ISP will delegate the rDNS if they thought
they could.
-wayne