Reverse DNS (PTR) Lookup

Find the PTR name for an IPv4 or IPv6 address and check it resolves back (forward-confirmed reverse DNS), as mail servers require.

Reverse DNS turns an address back into a name. Mail servers care most: they expect the sending server's address to have a PTR name that resolves back to the same address (forward-confirmed reverse DNS), and many reject or spam-flag mail when it doesn't. Enter an IPv4 or IPv6 address, or a host name to check every address it has. The PTR is set by whoever holds the address block (your ISP, host or cloud provider), not in your own domain's DNS.