Email spam blacklisting, Reverse-DNS, PTRs and you

Covering all DNS, MX, A Record, TXT records and more
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greg
Site Admin
Posts: 73
Joined: Mon Nov 28, 2005 3:01 pm

Email spam blacklisting, Reverse-DNS, PTRs and you

Post by greg »

If you use an Exchange server or other on-site email hosting service, sometimes you may notice you are being blacklisted on one of the internet spam blacklists, namely spamrats.com. You will see the listing due to this message: "It failed on the following criteria: Does IP Address comply with reverse hostname naming convention... Failed"

This is related to a reverse dns entry being incorrect. You can check if your business is compliant by going to http://www.dnsgoodies.com/ and in the Reverse DNS Lookup field, enter the external IP of your Exchange server. This IP should reverse-resolve to the MX record of the domain of your email. So, if your email address is someone@examplecompany.com, that IP should reverse-resolve to the IP of the MX record of examplecompany.com

You need to contact your ISP and get them to change it on their DNS server. It is called the PTR record. The change needs to be made on the DNS server of the company from which you lease your IP address. Your reverse DNS entry should resolve back to your mail server's public server name. ISP's don't do this unless specifically requested, and usually require a small one-time fee. If you need assistance with any of these steps, Pelstar is but a phone call away!
Greg Marlett
Forum Site Administrator
Pelstar Computer Systems
gmarlett@pelstar.com
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