I've noticed that some email servers are having a hard time looking up our reverse dns pointers, so i started looking into why this is. When i used dnsstuff.com, its output shows the following for one of the ip addresses on one of my email servers:
How I am searching:
Asking f.root-servers.net for 65.239.170.207.in-addr.arpa PTR record:
f.root-servers.net says to go to henna.arin.net. (zone: 207.in-addr.arpa.)
Asking henna.arin.net. for 65.239.170.207.in-addr.arpa PTR record:
henna.arin.net [192.26.92.32] says to go to ns1.iplt.twtelecom.net. (zone: 239.170.207.in-addr.arpa.)
Asking ns1.iplt.twtelecom.net. for 65.239.170.207.in-addr.arpa PTR record:
ns1.iplt.twtelecom.net [64.132.94.250] says to go to ns1.choicenet1.com. (zone: 239.170.207.in-addr.arpa.)
WARNING: Duplicate zone found (239.170.207.in-addr.arpa. is repeated). This can prevent the lookup from continuing
(BIND8 and BIND9 will cause a 'server failure' response). Although I will continue, be aware that
most DNS servers will not see your reverse DNS entry.
The problem here is that ARIN says that the zone 239.170.207.in-addr.arpa is handled by ns1.iplt.twtelecom.net (and other DNS servers), whereas ns1.iplt.twtelecom.net then says that the zone 239.170.207.in-addr.arpa is handled by ns1.choicenet1.com (and other DNS servers).
BIND can't handle this, and will stop the reverse DNS lookup. I believe BIND does this because it knows that the 239.170.207.in-addr.arpa zone is handled by ARIN, so therefore it would get stuck in a loop (going from ARIN to twtelecom.net and back to ARIN again).
To fix this, twtelecom.net would either need to tell ARIN to delegate the 239.170.207.in-addr.arpa zone directly to you, or if they want to keep control at ARIN, they need to find some other way to get the zone assigned to you (perhaps separate zones 0.239.170.207.in-addr.arpa, 1.239.170.207.in-addr.arpa, etc.).
-Scott
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