Glossary

PTR Record

Definition: Pointer record — a reverse DNS record that maps an IP address back to a domain name, used primarily for email server verification.

A PTR record (Pointer record) is the DNS record type used for reverse DNS lookup. While A records map domain names to IP addresses (forward DNS), PTR records map IP addresses back to domain names. PTR records are stored in the special in-addr.arpa zone (for IPv4) or ip6.arpa zone (for IPv6).

PTR Record Format

85.33.21.104.in-addr.arpa.  IN  PTR  mail.example.com.

The IP address is written in reverse order for IPv4: IP 104.21.33.85 → 85.33.21.104.in-addr.arpa.

Who Controls PTR Records?

PTR records are controlled by whoever owns the IP address block — usually your ISP or hosting provider. Unlike A or MX records, you cannot set PTR records yourself through a DNS panel unless your provider delegates the reverse zone to you. Contact your hosting or VPS provider to set or change a PTR record.

PTR Records and Email Deliverability

PTR records are critical for mail servers. Many spam filters perform a reverse DNS check on the sending server's IP address:

  1. The filter looks up the PTR record for the sending IP.
  2. It verifies the resolved hostname matches the claimed sending domain (forward-confirmed reverse DNS — FCrDNS).
  3. A missing or mismatched PTR record significantly increases the chance of email being marked as spam.

PTR Records for Network Troubleshooting

Tools like traceroute and nslookup use PTR records to display hostnames instead of raw IP addresses in network path outputs, making troubleshooting much easier.

Free Tools