Defaults.Exposed › Glossary › Reverse DNS (PTR record)

Reverse DNS (PTR record)

Also known as: PTR record, reverse lookup

The reverse of a normal lookup — it links a server's numbered address back to a name, which mainly affects whether your email is trusted or treated as spam.

What it is

A normal lookup turns a name into a numbered address. Reverse DNS does the opposite: it turns a numbered address back into a name, using a “PTR record.” Its most important everyday role is with email. When your mail server sends a message, the receiving system often checks the reverse lookup of the sending address to confirm it has a proper, matching name — a basic sign of a legitimate sender rather than a spam machine.

Why it matters to your business

If the server sending your email has no reverse DNS, or one that doesn’t match, receiving mail systems get suspicious. The result is your genuine emails landing in spam folders or being rejected outright — invoices, quotes, and replies that never reach the customer. Because the failure is silent, you often discover it only when someone says “I never got your email.” Correct reverse DNS is one of the quiet ingredients that keeps your business email landing in the inbox.

How to tell / what to do

The free check flags reverse-DNS problems for the address sending your email. Fixing it usually means a request to whoever provides your mail server or hosting, since it’s set on their side. Our reverse DNS fix guide explains what to ask for. It costs nothing and helps protect your email’s reach.

Want to fix this on your own domain? See the free guide →