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  1. #1

    PTR Record, what exactly does it do

    Hi There,

    Can anyone tell me or guide me to a right place where i can find out what exactly some ISP's do by checking the PTR record. I am quiet confused.

    Lets say i send an email via an ASP script from my server, does the ISP take the IP of the SMTP server and do a Revert PTR on that, or does the ISP check the "From" email address and do a reverse PTR on the domain of that email?

    Any advice would be very much appreciated.


  2. #2
    PTR is a reverse DNS record. Most SMTP servers do reverse DNS checking to allow or disallow acceptance of the message. The IP address of your server needs to both forward and reverse match. If your servers IP is and named If you do an nslookup on you should get and if you do it on you should get


  3. #3
    yes i have set my server name to and when you lookup it points to that IP and when you reverese lookup the ip it gives me but the problem is when i lookup my IP it gives me but it also addds a X.X.X.IN-ADDR.ARPA. extension to it. Does this matter?

  4. #4
    How are you looking up the IP address to see the reverse? Are you using nslookup? If so it should ONLY show you your servers Fully Qualified Domain Name (FQDN). if it says then you might have the zonefile configured incorrectly. Are you hosting the reverse record?


  5. #5
    If you are hosting the zonefile for it make sure your record in looks like this

    1 PTR

    If it is missing the ending . it will append the zonefiles name to the end of the record.


  6. #6
    i dont think i am hosting the zone file i am with EV1SERVERS. and i am using the following site to check the rever IP

  7. #7
    Then you should contact whatever company owns that IP address and ask them to put the period at the end of for your IP in there record. If you want me to verify what your saying just PM me the IP addres "if you don't want to publish it on here".

  8. #8
    Join Date
    Jan 2002
    yes, it is normal to have appended to your ip address when you do a ptr lookup.
    Ahmad Alhashemi
    PHP, Apache, C, Python, Perl, SQL
    18 related BrainBench certificates

  9. #9
    When I enter any of my IP addresses or any other IP's I can think of i don't get appended to the domain name it responds with in that URL he gave me.


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