A PTR (Pointer) record does the exact opposite of an A Record. While an A record translates a domain name into an IP address (Forward DNS), a PTR record translates an IP address back into a domain name. This process is known as Reverse DNS (rDNS).
Check if your mail server's IP address correctly maps back to your hostname to avoid spam filters.
The primary use case for PTR records is anti-spam verification for email servers. When your mail server tries to deliver an email to a receiving server (like Gmail or Yahoo), the receiving server looks at the IP address the connection is coming from.
It then performs a Reverse DNS lookup (checking the PTR record) to see if the IP address claims to be associated with a valid hostname. If the PTR record is missing, or if it doesn't match the sender's domain, the receiving server will view the email as highly suspicious and likely reject it or mark it as spam.
This is the most common point of confusion. You cannot set a PTR record at your domain registrar (like GoDaddy or Namecheap). PTR records are controlled by the entity that owns the IP address. You must contact your web host, ISP, or cloud provider (like AWS, DigitalOcean, or Linode) to set the Reverse DNS for your server's IP.
While technically possible, it is highly discouraged. Having multiple PTR records for a single IP address can cause unpredictable behavior in spam filters. If you host multiple websites on one server, the PTR record should point to the server's primary hostname, not the individual hosted domains.
To make Reverse DNS work within the standard DNS hierarchy, IPv4 addresses are reversed and appended to the special in-addr.arpa domain. For example, to find the PTR record for the IP 192.0.2.1, a DNS query is made for 1.2.0.192.in-addr.arpa.