DNS lookup

Check the reverse DNS name of an IPv4 or IPv6 address

A PTR record maps an IP address back to a host name. Enter an IPv4 or IPv6 address, and the tool builds the reverse name and asks for its PTR.

What the PTR record shows

The owner of the IP block sets the PTR record, not the owner of the domain. For 203.0.113.7 the query goes to 7.113.0.203.in-addr.arpa.

Mail servers compare the PTR with the name the sender introduces itself with and mark mismatches as spam. A name like 7-113-0-203.static.example.net points to a hosting or ISP range.

When you need it

Check the PTR of your mail server before a campaign
Find the provider behind an IP from your logs or a proxy list
See the name that sites and anti-fraud systems see for your address

Questions about DNS records

01Who sets the PTR record?

The owner of the IP range: your host or ISP. Ask them to set it, since your domain's DNS panel cannot change it.

02Why do mail servers care about PTR?

A missing or generic PTR looks like a home or hijacked machine. Many receivers reject or down-rank mail from such addresses.

03Why does the PTR differ from my site's domain?

The PTR belongs to the server, and one server often hosts many sites. For mail, the PTR must match the name of the sending server, not every site on it.

04What is FCrDNS?

Forward and reverse records agree: the PTR of an address points to a name, and the A record of that name returns the same IP. Mail servers check this match and score letters lower without it.

05How many PTR records should one IP have?

One. The standard allows several, but mail servers take the first name, and extra PTR records confuse the FCrDNS check.