PTR Record — Reverse DNS

What is a PTR record

A PTR record is the reverse of an A record: given an IP address, it returns a hostname. It is commonly known as Reverse DNS (rDNS).

How it is defined

It is not defined in your own DNS zone — it is defined by the owner of the IP address (typically your network provider or hosting provider). The PTR record lives in special zones:

• IPv4: {reversed-ip}.in-addr.arpa
• IPv6: {reversed-hex}.ip6.arpa

Example

For the IP 93.184.216.34, the PTR record would be:

34.216.184.93.in-addr.arpa.  IN  PTR  example.com.

For IPv6 2606:2800:220:1:248:1893:25c8:1946:

6.4.9.1.8.c.5.2.3.9.8.1.8.4.2.0.1.0.0.0.0.2.2.0.0.0.8.2.6.0.6.2.ip6.arpa.  IN  PTR  example.com.

Why it matters

• Email deliverability: when you send email, the receiving server performs an rDNS lookup on your IP. If the PTR is missing or does not match the hostname you declare in the SMTP HELO, your mail is treated as suspicious.
• Network diagnostics: when you run traceroute you see hostnames instead of unknown IPs.
• Logging & security: log analyzers show meaningful hostnames instead of raw IPs.

Forward-confirmed reverse DNS (FCrDNS)

To be considered "valid" by auditors and mail servers, the PTR must be forward-confirmed:

1. IP 93.184.216.34 → PTR returns example.com.
2. Forward lookup of example.com → A returns 93.184.216.34.

Both must match. If not, it is "mismatched rDNS" and reduces mail reputation.

How to request it

If you have a dedicated IP from your hosting provider, ask them to set the PTR to your mail server's hostname. If you are on shared hosting, the PTR typically points to a hostname owned by the provider and cannot be changed.