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Reverse DNS lookup.

Look up an IP address's PTR record (the hostname it reverses to) and find out whether that hostname points back to the same IP (forward-confirmed rDNS). Enter any IPv4 or IPv6 address; the check runs against live DNS. No account, no card.

Enter an IPv4 or IPv6 address. We resolve its PTR record (the hostname the IP reverses to) and check whether that hostname points back to the same IP (forward-confirmed rDNS).

What a reverse DNS lookup tells you

A PTR record maps an IP address back to a hostname. For anyone sending email, the lookup answers two practical questions:

Does this IP have reverse DNS at all?
A sending IP with no PTR record is a red flag to receiving mail servers - many defer or reject it outright. This is the fastest way to catch a missing PTR before it costs you the inbox.
Is the rDNS forward-confirmed?
The tool re-resolves each PTR hostname and checks it points back to the queried IP. Matching in both directions (FCrDNS) is the trusted setup mailbox providers look for from bulk senders.

Why it matters for sending mail

Reverse DNS is one of the cheapest reputation signals to get right, and one of the most common to overlook. Some blocklists reject purely on it - SpamRats keeps a list dedicated to IPs with missing or generic PTR records, and mail from a listed IP can be blocked before it's even read. It's also step zero when you bring a new sending IP online: set a forward-confirmed PTR before you start warming up the domain and IP, so every message counts toward the reputation you're building rather than against it.

Reverse DNS lookup FAQ

Reverse DNS is the opposite of an ordinary lookup: instead of turning a hostname into an IP, it turns an IP into a hostname. It's published as a PTR record in the reverse zone (in-addr.arpa for IPv4, ip6.arpa for IPv6) and it's controlled by whoever owns the IP block, usually your hosting or IP provider, not your domain's own DNS.

When your server connects to deliver mail, the receiving server looks up the PTR record of the connecting IP as a basic sanity check on the sender. An IP with no PTR record (or a generic, provider-default one) looks suspicious, and its mail is far more likely to be deferred, filtered, or rejected. Every IP you send production email from should have a matching PTR record.

FCrDNS means the two directions agree: the IP's PTR record points to a hostname (say mail.example.com), and that hostname's forward A/AAAA record points back to the same IP. When both sides match, the reverse DNS is "forward-confirmed" - the strongest, most trusted form, and what large mailbox providers expect from bulk senders. A PTR that doesn't forward-resolve back is weaker and can be treated as unverified.

You set the PTR record with whoever controls the IP (your hosting company, VPS or cloud provider, or ESP), not in your own domain's DNS zone. Give them the hostname you want the IP to reverse to, then make sure that hostname also has a forward A/AAAA record pointing back to the IP, so the result becomes forward-confirmed. Changes can take a while to propagate; re-check with this tool afterwards.

Reverse DNS set - now send to a clean list

A forward-confirmed PTR protects your sender reputation; verifying your list keeps bounces and spam traps from undoing that work. Start free with 100 credits, no card required.

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