DNS can be tricky. There is a lot to know and, even when you think you have a firm grasp on it, surprises still pop up. Reverse DNS and PTR record configuration is one of those sneaky topics, but it's crucial to SPAM prevention during email delivery.
Add a new PTR record and for the name, enter the final digit of the IP address that you’re setting up the reverse record for. In our example, 100. For the Canonical Hostname, enter the domain name you’d like the IP address to resolve to, for instance mailserver.example.com. After you’ve saved your zone file, allow some time for the change to propagate before validating the new reverse DNS record.
You must create the reverse DNS zone on the authoritative DNS nameserver for the main IP address of your server. You can find out which nameserver is the authoritative server by entering the IP address you’re trying to configure into the DIG Web Interface. If the Reverse response is not provided by your nameserver, you’ll need to contact your hosting provider to help you set a PTR record.
You should be able to accomplish that be emailing their support team and letting them know you’d like a PTR record set for the IP address X.X.X.X resolving to yourdomain.example.com. If you are in control of the authoritative nameserver, the first step is to create a reverse DNS zone. The hostname for the zone has to be in a very specific format. It starts with a portion of your IP address written backward followed by .in-addr.arpa.