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I need to check a reverse dns using the DNS servers of some domains. But I'm having some problems.

dig -x 212.26.146.21 +short
mx20.gypost.com.

all ok

dig -x 212.26.146.21 @8.8.8.8 +short
mx20.gypost.com.

its ok too

dig SOA google.com +short 
ns1.google.com. dns-admin.google.com. 2014021800 7200 1800 1209600 300

dig -x 212.26.146.21 @ns1.google.com +short

empty

I can't find reverse address using NS record of any domain. What i do wrong? And how i can check my reverse address using dns server of gmx.com, for example.

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Answer for reverse DNS records is other dns-servers then for not reverse. You can look full dns mechanism by command:

$ dig -x 212.26.146.21 +trace

And easy way for get dns-server which you need:

$ dig -x 212.26.146.21 PTR

See AUTHORITY SECTION:

;; AUTHORITY SECTION:
146.26.212.in-addr.arpa. 172799 IN  NS  ns2.adamant.net.
146.26.212.in-addr.arpa. 172799 IN  NS  ns2.lucky.net.
146.26.212.in-addr.arpa. 172799 IN  NS  ns2.iptcom.net.
146.26.212.in-addr.arpa. 172799 IN  NS  ns.adamant.net.

Then:

$ dig -x 212.26.146.21 +short @ns2.lucky.net.
mx20.gypost.com.
  • Some domains can't send mails to my domain. I can't now add log but there some like "cant find reverse dns". How i can find dns server of some domain then? – Kostiuk Aleksandr Sep 10 '14 at 8:25
  • You must know the IP from which your server sends emails. Also you must know helo string, which your mail server sends to others in SMTP protocol. And you must ask your provider, which give you IP for he set PTR on this IP to your hostname. Also you must set A record for this helo to right IP. – loooser Sep 10 '14 at 8:36
  • In other words, resolving IP->hostname must be the same as reversed hostname->IP, and this hostname must be set as helo/ehlo string in your mail server. – loooser Sep 10 '14 at 8:44
  • The fact is that sometimes only letters do not reach. And only some domains. For example, no problem with google. – Kostiuk Aleksandr Sep 10 '14 at 9:04
  • Because only some mail servers check this fact and reject emails from IP which has not reverse dns. – loooser Sep 10 '14 at 9:07

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