Pro move: type dmarc:yourdomain.com or blacklist:1.2.3.4 straight into the box — it switches tools for you.
About this tool. A PTR record maps an IP address back to a hostname — the reverse of an A record. Mail servers without matching forward and reverse DNS get their email rejected by many providers, so this is a must-check for any server that sends mail.
How to read your reverse dns (ptr) lookup results
Reverse DNS (a PTR record) maps an IP address back to a hostname. Mail servers check it to judge sender legitimacy.
For a mail server, the PTR should resolve forward to the same IP (matching forward and reverse DNS).
Common problems and how to fix them
Your mail is treated as suspicious
Set a PTR record for your sending IP that matches your mail hostname, and make sure that hostname resolves back to the same IP. Your hosting provider sets the PTR, not your DNS host.
Common questions.What is reverse DNS?
It is the lookup from an IP address to a hostname, using a PTR record, the opposite direction of a normal lookup.
Why does reverse DNS matter for email?
Receiving servers distrust senders whose IP has no PTR or whose PTR does not match. Matching forward and reverse DNS improves deliverability.