I have one for you DNS experts out there.
We host DNS for a client that runs his own mail server, and we have received delegation from AT&T for his IP block.
I can see nothing wrong in our setup, yet some places can see the PTR record for his mail server's IP address, and some cannot. I have synchronized the name servers so they have exactly the same info.
I can see something wrong:
The online Dig tool at Men and Mice shows the reverse lookup just fine, nslookup shows it also. But DNSReport.com reports that the server's address has no reverse lookup, as does DNSStuff.com
http://www.dnsstuff.com/tools/ptr.ch?ip=12.20.208.99 shows that AT&T is delegating the reverse DNS for 12.20.208.99 to dns.skywaves.net, using the hostname 99.96/28.208.20.12.in-addr.arpa. But dns.skywaves.net doesn't have a PTR record for 99.96/28.208.20.12.in-addr.arpa.
The reason I don't like Men and Mice's DIG tool is this -- it displays the results you want to see, not the results that you should see. If you enter "28.208.20.12.in-addr.arpa" as the "Domain Name", choose PTR, and leave "Name Server" (BAD option!!!) blank, you'll get the SOA record, indicating that the record doesn't exist.
-Scott
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