PTR record

A PTR record (pointer record) is a reverse-DNS entry that maps an IP address back to a domain name. It is the inverse of an A record: where an A record answers "which IP does this name have," a PTR record answers "which name is behind this IP."

What a PTR record involves

Reverse DNS lookups happen in a special in-addr.arpa zone (for IPv4) or ip6.arpa (for IPv6), where the IP address is written in reversed order. The key difference from other records: a PTR is published in a zone belonging to the owner of the IP address pool, not the domain owner. In practice this means:

• the PTR record is set by the hosting, VPS or network provider,
• you cannot change it in your own domain's ordinary DNS panel,
• good practice is for the PTR and the A record to point at each other consistently (forward-confirmed rDNS).

The PTR record in practice

The PTR record's most important role is mail server reputation. Receiving SMTP systems check whether the sender's IP has a valid, matching PTR record — its absence or a default "generic" provider name often means the message is rejected outright or flagged as spam. That is why, when running your own mail server on a VPS, configuring the PTR record — alongside SPF, DKIM and DMARC — is one of the first steps. Beyond email, rDNS is also used in logs and diagnostic tools.