check_reverse_dns
Check a sending IP's forward-confirmed reverse DNS (FCrDNS) to verify its PTR record resolves back to the same address, exposing mismatches or missing PTRs that harm email deliverability.
Instructions
Check one sending IP's forward-confirmed reverse DNS (FCrDNS): reads the IP's PTR record, then resolves that hostname back and reports whether it returns to the same IP. verdict is confirmed (the pair agrees — what receivers want to see), ptr_missing (the IP publishes no reverse record), or mismatch (a PTR that does not resolve back). A PTR on its own proves nothing, because the IP's operator writes its own reverse zone — only the forward confirmation is evidence, so never report a bare PTR as verified. The fix is always made by whoever controls the IP (the hosting or mail provider), never in the sending domain's own DNS. Pass a public IPv4 or IPv6 address.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| ip | Yes | The sending IP to check, IPv4 or IPv6. Must be a public address — private, loopback and CGNAT ranges have no meaningful reverse DNS and are refused. |