What Is a PTR (Reverse DNS) Record?

A PTR (Pointer) record, also known as a Reverse DNS record, maps an IP address back to a domain name. It performs the opposite function of an A record, which maps a domain name to an IP address. PTR records are stored in special reverse DNS zones and are primarily used to verify that an IP address is legitimately associated with a sending domain.

Reverse DNS lookups are widely used in email authentication, network diagnostics, and spam prevention. When a receiving mail server checks the PTR record of an incoming connection, it confirms whether the sending IP resolves to a recognizable and valid domain name. If no PTR record exists, or if the reverse lookup result doesn’t match the expected hostname, the email may be treated as suspicious or rejected.

How PTR (Reverse DNS) Records Work

PTR records reside in the reverse DNS namespace, which mirrors the normal DNS structure but in reverse order. For IPv4, the reverse zone ends in .in-addr.arpa, while IPv6 uses .ip6.arpa.

For example, if a mail server uses the IP address 192.0.2.10, the corresponding PTR record might look like this:

When the receiving server performs a reverse DNS lookup, it retrieves the PTR record and verifies that the result (in this case, mail.example.com) matches the hostname declared during the SMTP handshake or other forward DNS lookups. Consistency between forward and reverse records improves the sending server’s reputation and helps mail pass anti-spam checks.

Why PTR Records Are Important for Email Delivery

PTR records serve as a fundamental trust signal for inbound mail servers. Many receiving systems perform reverse DNS validation before accepting or scoring incoming messages. If an IP address lacks a valid PTR record, the message may be delayed, filtered, or rejected outright.

Best practices include:

• Ensure every mail-sending IP address has a matching PTR record
• Align the PTR record with the domain used in the SMTP HELO or EHLO command
• Maintain consistency between reverse and forward DNS entries
• Avoid generic or mismatched hostnames that can trigger spam filters

While PTR records are not authentication mechanisms like SPF or DKIM, they contribute to sender reputation and are part of the broader framework that mailbox providers use to evaluate message legitimacy.

PTR Records and DMARCeye

DMARCeye analyzes PTR and other DNS records to help organizations identify misconfigurations that could affect deliverability. By monitoring IP addresses associated with your outgoing mail and correlating them with DMARC, SPF, and DKIM results, DMARCeye ensures your domain maintains a trustworthy technical footprint.

The platform highlights missing or incorrect reverse DNS entries, helping you fix alignment issues that could harm sender reputation. With complete visibility into your DNS and authentication setup, DMARCeye strengthens domain credibility and ensures consistent message delivery across all mail servers.

Sign up for a free trial of DMARCeye today and secure your email domain.

To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.