Revese DNS setting is not correct.

Posted on 2014-08-01
Last Modified: 2014-09-01

We are hosting Our Exchange 2007 server inside our firewall.

Most emails to external domains are fine.

But Some emails to external domains return with revers DNS incorrect error message.

I checked with my ISP, Reverse DNS is setup correctly and points to the IP address of the email server.

But the error message refers to the IP address of the outside interface of the firewall instead of the email server.

Why so?

And how to correct it.


Question by:Roger38
    LVL 24

    Accepted Solution

    Your internal to external NAT is not correct. you should NAT your email server internal IP to the email server public IP.
    i.e. internal to external NAT should be like this as an example (>  assuming is your server internal IP and is your email server public IP.

    After NAT please open this site from the exchange server to make sure your NAT is correct.

    Author Comment


    If that's the case, why does it work OK, with majority of the external domains?


    LVL 24

    Expert Comment

    Did you check the ip address by visiting the above site?

    It will work even if you dont have PTR created. for example your email will work well with gmail, yahoo.
    But some of the antispam system will consider your emails as spam without PTR

    Author Closing Comment


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