Normally when we do a DNS lookup, we check a domain for an associated IP. Reverse DNS is used to check an IP for an associated domain name. For this to work, you need a PTR record in the  IP address zone file. These records do not go in your domains zone file. PTR records are generally maintained by the owner of the IP, most likely your hosting provider or whoever you may be leasing your IP address from.

On a server, the mail server relies heavily on RDNS to verify the sender of a message. If the sending hostname does not match the PTR record, then your message may not authenticate properly with other hosts. When setting your PTR record it is important to set it correctly to the hostname that will be sending the email. By default on cPanel and Plesk servers, the hostname sends all of the mail, therefore your PTR record should match the hostname of the server. If the records don’t match, your emails may be marked as spam, or the IP address could be blacklisted by major email providers!

To test your RDNS, you can run the following commands in your terminal:

~: dig -x 204.12.243.118

host.subversive-host.com

We see that the RDNS answered with the PTR record and  resolves to host.subversive-host.com, now if we dig the hostname, we should come up with the same IP address:

~: dig host.subversive-host.com

204.12.243.118

They both match!

If we got a response from that second command like:

~: dig host.subversive-host.com

10.5.5.5

Then your RDNS lookup would not match and would likely cause problems with e-mail routing.

Most hosts should have this setup for you by default, but if they don’t you may have to find your way through their documentation on how to setup a PTR record for your IP.

If you don’t have a terminal

You can use a web-based DNS checker to check your RDNS. We like IntoDNS.com, they have a pretty good tool that will give you a ton of information about your the DNS for your domain.

 

As always, if you ever need help, our technicians are available 24/7 365 to assist!