A PTR record, short for Pointer Record, is a type of Domain Name System (DNS) record used for reverse DNS lookups. It maps an IP address back to a domain name, providing the opposite function of an A record.
A PTR record enables reverse DNS resolution by connecting an IP address to its associated hostname. When someone performs a reverse DNS lookup, the PTR record is queried to identify which domain name corresponds to the given IP address.
PTR records are widely used for security, troubleshooting, and email authentication. In email systems, they help confirm that the sending mail server’s IP address matches the domain name used in email headers. This verification builds trust with internet service providers (ISPs) and reduces the risk of emails being flagged as spam.
The process for using PTR records involves:
For example, if an email originates from the IP address 203.0.113.10, the PTR record might resolve it to mail.example.com. This confirms that the IP is legitimately associated with the sending domain.
PTR records matter because:
If a mail server lacks a valid PTR record, many receiving servers may reject or flag its emails as suspicious.
PTR records are commonly used for:
Example scenario: An organization sets up PTR records for its email servers so that the recipient’s mail system can verify any outgoing message during reverse DNS checks.
While not mandatory by protocol, most ISPs require a valid PTR record to accept emails reliably.
An A record maps a domain name to an IP address, while a PTR record maps an IP address back to a domain name.
PTR records are managed by the owner of the IP address, usually the hosting provider or ISP.
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