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I have 2 servers :

  1. Web Server (on AWS) for : mydomain.com on IP : X.X.X.1
  2. Mail Server (on Plesk Ubuntu) for : mail.mydomain.com on IP : X.X.X.2

And I have a reverse DNS Spam issue so I would like to set my reverse DNS correctly. So I came to X.X.X.2 and wanted to set my rDns settings to mydomain.com, but my Plesk-Ubuntu hosting provider send me an error message to say that mydomain.com does not resolve X.X.X.2.

How should I set the reverse DNS configuration in this case ?

Maxime NGOE
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1 Answers1

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The PTR record should have a matching A record. While the RFC 1912, 2.1 is only informational,

Some receiving mail servers may use this as an indication of a possible spam source in a scoring system. Most will not reject incoming mail solely on this basis. We recommend that you contact your ISP and ask them to setup a reverse record (PTR) that matches the hostname of your mail server. (MXToolBox Inc., SMTP Reverse DNS Mismatch)

Now that you have:

example.com.            IN   A    192.0.2.1
mail.example.com.       IN   A    192.0.2.2

You should have

2.2.0.192.in-addr.arpa. IN   PTR  mail.example.com.

while you are trying to set

2.2.0.192.in-addr.arpa. IN   PTR  example.com.

instead, giving you the (clear and unambiguous) "example.com does not resolve to 192.0.2.2" error.

In order to handle the original problem you should also use mail.example.com as your SMTP banner:

It is best practice to put the name of your server in your SMTP banner so that anybody who connects via your IP Address has a clue as to who they are talking to. You will get this warning if the name you present yourself as is not in the same domain as the hostname we get when we perform a PTR lookup on your IP Address.

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Esa Jokinen
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