Why PTR (Reverse DNS) Validation Matters

A PTR (Pointer) record is the reverse of an A record — it maps an IP address back to a domain name.
In email infrastructure, proper PTR configuration is critical for passing spam and security checks.

• Anti-spam filters often reject or penalize mail servers without valid PTR records.
• PTR validation ensures your server IP resolves to a hostname that resolves back to the same IP.
• Misconfigured or missing PTR records can lead to mail delivery issues, blacklisting, or failed SPF/DMARC checks.

This tool helps you identify whether included SPF domains have valid and consistent PTR records.

Note: This tool detects ip4: and ip6: ranges using CIDR notation (e.g., 192.0.2.0/24) but does not expand and validate each individual IP within the range.

If a CIDR block is found, the tool estimates how many IP addresses it includes and warns you if the range appears excessively large (typically anything larger than 1,023 IPs).
Large IP ranges in SPF records may lead to delivery issues or violate SPF DNS lookup limits. Review such entries carefully.

Result Legend:

• Valid: PTR record exists and forward resolves back to the original IP. PTR loop is complete.
• Mismatch: PTR exists, but the hostname does not resolve back to the original IP. Loop is broken.
• No PTR: No PTR record found — reverse DNS is not configured.