Reverse DNS (PTR Records)

The "phone book in reverse." Reverse DNS (rDNS), using a PTR record, does the opposite of an record: it maps an IP address back to a domain name. Mailbox providers require this "reverse lookup" to prove your IP is a legitimate mail server.

11 questions in this topic

What is Reverse DNS (rDNS)? What is a PTR (Pointer) record? What’s a PTR record (reverse DNS) and why is it important? Why is a valid PTR record important for email deliverability? How does rDNS affect email authentication? How do I set up a PTR record for my sending IP? Does my hostname need to match my rDNS lookup? (Forward-confirmed reverse DNS - FCrDNS) How does rDNS mapping confirm sender identity? How do ISPs use reverse DNS in trust scoring? How to check and verify PTR alignment? What happens if PTR and HELO don’t match?

Questions about Reverse DNS (PTR Records)