Reverse DNS

What reverse DNS is

Reverse DNS maps an IP address back to a name using a PTR record under in-addr.arpa (IPv4) or ip6.arpa (IPv6). It is set by whoever controls the IP range, usually your hosting provider or ISP, not in your own domain's DNS.

The tool also checks forward confirmation: it looks up the PTR name's A or AAAA records and confirms they include the original address. Mail servers and many security tools only trust a reverse name that passes this round trip.

Why it matters for email

Gmail, Microsoft and most mail servers reject or junk mail from an IP without a matching reverse name. If you run a mail server, ask your provider to set the PTR to the server's hostname (for example mail.example.com) and make sure that name resolves back to the same IP.

Questions

How do I change a PTR record?

In your cloud or hosting provider's control panel, usually next to the server's IP address. For addresses from an ISP, ask the ISP. You can't set it in your domain's DNS zone.

What does "not forward-confirmed" mean?

The IP points to a name, but that name doesn't point back to the IP. Add an A or AAAA record for the name, or change the PTR to a name that already resolves to the address.