Reverse DNS Lookup
Find the host name behind an IP address. Free, no sign-up
How the check works
First the address's PTR record is looked up: the name the holder of the address has set for it. Then each name it gives, up to three, is looked up forward — its A record for an IPv4 address, its AAAA record for an IPv6 one — and the addresses it has are compared with the one you typed.
A name that points back to the same address is forward-confirmed (FCrDNS). Many mail servers look for that in a server sending to them; a mail server's address should have it.
Questions about this tool
What is reverse DNS?
Ordinary DNS turns a name into an address; reverse DNS turns an address into a name. It is a PTR record at a name built from the address, such as 7.113.0.203.in-addr.arpa for 203.0.113.7.
Who sets the reverse DNS of an address?
Whoever holds the address — usually your hosting, server or internet provider — and not the DNS of your domain. To set or change it, ask them, or use their control panel where it offers the setting.
What does forward-confirmed mean?
That the name the PTR record gives points back to the same address: the address's PTR says mail.example.com, and the A or AAAA record of mail.example.com holds that same address. It is called forward-confirmed reverse DNS, or FCrDNS.
Why does reverse DNS matter for email?
Many receiving mail servers check the address a message comes from. A sending server whose address has no reverse DNS name, or a name that does not point back, is more likely to have its mail refused or treated as spam.