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How to configure Reverse DNS, PTR and MX records for private email server behind Comcast Static IP
Hello, I have some questions on how to set-up Reverse DNS, PTR and MX records for our private Exchange email server sitting behind a Comcast Static IP address.
We run our own Exchange server on a private network behind static IP address: 70.91.104.193. Our domain is www.estarmail.com and mail.estarmail.com for email. I have registered these domains and set up Reverse DNS, PTR and MX records at REGISTER.COM our registrar.
When I go to DNSQUERY.COM I get no results for A, CNAME, MX and TXT queries. The DNS and PTR query properly return estarmail.com for my IP. The reverse DNS query returns an undefined (???) PTR to my domain. The WHOIS query returns Comcast Business Communications, LLC.
What can I do to get the various missing or incorrect DNS records set up so they will resolve properly to our static IP and domain?
Martin Kultermann
eStar Communications
Office: +1 (773) 697-8283
Cell: +1 (847) 372-2381
Email: Martinator@eStarMail.com
Accepted Solution
tmittelstaedt
Problem solver
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326 Messages
8 years ago
A domain registry like register.com is only authoratative for forward records like A records and MX records. You can only setup PTR records with the hoster of the IP address block - in this case Comcast.
The by the book process is contact Comcast on the phone Mon-Fri 8-5pm Eastern time.
Incidentally your PTR isn't correct. Take a look at the following:
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Users\tedm>nslookup
Default Server: UnKnown
Address: 172.16.1.13
> set type=mx
> estarmail.com
Server: UnKnown
Address: 172.16.1.13
Non-authoritative answer:
estarmail.com MX preference = 0, mail exchanger = mail.estarmail.com
estarmail.com nameserver = dns142.a.register.com
estarmail.com nameserver = dns167.b.register.com
estarmail.com nameserver = dns223.c.register.com
estarmail.com nameserver = dns249.d.register.com
mail.estarmail.com internet address = 70.91.104.193
dns142.a.register.com internet address = 216.21.231.142
dns167.b.register.com internet address = 216.21.232.167
dns223.c.register.com internet address = 216.21.235.223
dns249.d.register.com internet address = 216.21.236.249
> set type=a
> mail.estarmail.com
Server: UnKnown
Address: 172.16.1.13
Non-authoritative answer:
Name: mail.estarmail.com
Address: 70.91.104.193
> set type=ptr
> 70.91.104.193
Server: UnKnown
Address: 172.16.1.13
Non-authoritative answer:
193.104.91.70.in-addr.arpa name = estarmail.com
------>>>>>>>>>>>>>>>>>>>>>>>>>>^^^^^^^^^^^^^
(should be mail.estarmail.com)
91.70.in-addr.arpa nameserver = dns104.comcast.net
91.70.in-addr.arpa nameserver = dns102.comcast.net
91.70.in-addr.arpa nameserver = dns103.comcast.net
91.70.in-addr.arpa nameserver = dns105.comcast.net
91.70.in-addr.arpa nameserver = dns101.comcast.net
dns101.comcast.net internet address = 69.252.250.103
dns101.comcast.net AAAA IPv6 address = 2001:558:fe23:8:69:252:250:103
dns102.comcast.net internet address = 68.87.85.132
dns102.comcast.net AAAA IPv6 address = 2001:558:1004:7:68:87:85:132
dns103.comcast.net internet address = 68.87.76.228
dns103.comcast.net AAAA IPv6 address = 2001:558:1014:c:68:87:76:228
dns104.comcast.net internet address = 68.87.68.244
dns104.comcast.net AAAA IPv6 address = 2001:558:100a:5:68:87:68:244
dns105.comcast.net internet address = 68.87.72.244
dns105.comcast.net AAAA IPv6 address = 2001:558:100e:5:68:87:72:244
>
Forward and reverse records only exist for hostnames not domains.
A domain (estarmail.com) can have a MX record and it can have an A record but the MX
record is only used for routing mail. The A record is not. CNAME records are not used
for routing mail at all. Setting a PTR (reverse DNS) record to point to a domain instead of
a hostname is nonsensical.
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Accepted Solution
Martinator
New problem solver
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2 Messages
8 years ago
Thank you, I have updated the PTR record at REGISTER.COM and opened a ticket at Comcast.
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