Reverse DNS (PTR) Lookup
Check the reverse DNS (PTR) record for any IP address - sending IPs without one are treated as suspicious.
What is reverse DNS (PTR)?
Reverse DNS maps an IP address back to a hostname using a PTR record - the opposite of a normal A record lookup, which maps a hostname to an IP. Enter a sending IP above and this tool reports whether it has a PTR record and what hostname it points to.
For email it matters a lot. Receiving servers routinely check whether a sending IP has valid reverse DNS, and mail from an IP without a PTR record is frequently treated as suspicious, deprioritized, or rejected outright. It's one of the oldest and cheapest signals a receiver uses to separate real mail servers from compromised machines.
Forward-confirmed reverse DNS (FCrDNS)
A PTR record on its own isn't enough - receivers want it to match. Forward-confirmed reverse DNS means the IP's PTR points to a hostname, and that hostname's A record resolves back to the same IP. The loop has to close in both directions.
So a dedicated sending IP of 203.0.113.10 should have a PTR pointing to something like mail.yourdomain.com, and mail.yourdomain.com should have an A record pointing back to 203.0.113.10. When both agree, the IP has a verifiable identity and receivers treat it as a legitimate mail server.
Who sets it, and when it matters
Reverse DNS is controlled by whoever owns the IP block - your hosting, VPS, or infrastructure provider - not your domain registrar. You typically set it in the provider's control panel or by opening a support request for the IP.
If you send through a managed provider like Google Workspace or Microsoft 365, they own the sending IPs and their reverse DNS is already correct, so there's nothing for you to do. PTR becomes your responsibility only when you send from your own dedicated IPs, which is exactly when this check is worth running.
Frequently asked questions
What is a PTR record?
A PTR record maps an IP address to a hostname - reverse DNS. Mail servers check it to confirm a sending IP has a legitimate identity rather than being an anonymous or compromised host.
Does missing reverse DNS hurt deliverability?
Yes. Many receivers penalize or reject mail from IPs without a PTR record. Any dedicated sending IP should have forward-confirmed reverse DNS, where the PTR hostname resolves back to the same IP.
What is forward-confirmed reverse DNS?
It means the IP's PTR points to a hostname, and that hostname's A record points back to the same IP. Receivers check that the loop closes in both directions before trusting the IP as a mail server.
Who sets the PTR record?
The owner of the IP block - usually your hosting or infrastructure provider - sets reverse DNS, not your domain registrar. You often request it through their control panel or support.
Do I need to worry about PTR on Google or Microsoft?
No. Managed providers own their sending IPs and keep reverse DNS correct. PTR is only your concern when you send from your own dedicated IPs.
Next steps
Stop configuring DNS by hand
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