Simple definition
A PTR record is a reverse-DNS record that maps an IP address to a host name.
Technical definition
IPv4 reverse lookups use the in-addr.arpa namespace, while IPv6 uses ip6.arpa. The reverse zone is normally controlled by the organization that manages the IP address block rather than simply by the domain owner.
How it works / role
The resolver converts the IP address into a reverse-query name and requests the matching PTR record. The result can be used by diagnostic tools and by services such as email to compare a server’s announced identity with its address.
What is it used for?
Identify the name associated with an IP address, improve network diagnostics, and support reputation or consistency checks for mail servers.
Practical example
The public IP of an SMTP server has a PTR pointing to mail.example.com, consistent with the name used by the server.
Common issues
- PTR is missing or points to a generic name
- PTR does not match the SMTP server identity
- Reverse zone is controlled by the ISP and cannot be edited directly
- Forward-confirmed reverse DNS is inconsistent
Key takeaway: PTR records belong to the reverse-DNS zone controlled by the IP-address owner; they are not simply created in the domain’s normal forward zone.