Find the hostname an IP address maps back to, using its PTR record.
Enter an IPv4 or IPv6 address to find its hostname.
A reverse lookup goes the opposite way to a normal DNS query: instead of resolving a name to an IP, it resolves an IP back to a hostname using a PTR record. Reverse DNS is widely used by mail servers to check that a sending IP has a matching hostname.
Many receiving mail servers reject or downrank mail from IPs with no PTR record. This tool shows the hostname an address currently resolves to.
Receiving mail servers commonly check that the sending IP has a valid PTR record, and that it aligns with the sending hostname. Missing or mismatched reverse DNS is a frequent cause of mail being marked as spam.
The owner of the IP address block sets PTR records, which usually means your hosting provider or ISP rather than your domain registrar. To change reverse DNS you normally request it through whoever provides the IP.
Not every IP has a PTR record configured. Residential and some cloud IPs may have generic or missing reverse DNS. For mail-sending IPs, you should ask your provider to set a proper PTR record.
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