Perform a reverse DNS lookup to find the PTR record for any IP address, and verify forward-confirmed reverse DNS, critical for inbox placement.
Paste an IPv4 address like 8.8.8.8 or an IPv6 address, both are fully supported.
Choose your preferred resolver: Google, Cloudflare, OpenDNS, or Quad9.
We find the PTR hostname, then resolve that hostname forward again to confirm it points back to the same IP (FCrDNS).
Each check is shown pass/warn/fail with a plain-English explanation of what it means and what to fix.
The PTR record exists and is forward-confirmed. Your sending IP is properly identified by receiving mail servers.
A PTR record exists and FCrDNS passes, but something looks off, like a generic or dynamically-assigned-looking hostname. It works, but is worth improving.
No PTR record, or the hostname does not resolve back to the IP. This is one of the most common causes of email being rejected, contact your hosting provider or ISP.
A PTR (pointer) record is the DNS record used for reverse DNS lookups, mapping an IP address back to a hostname. Unlike A records, which go from name to IP, PTR records go in the opposite direction.
PTR records live in the in-addr.arpa (IPv4) or ip6.arpa (IPv6) zone and map an IP back to a hostname, the opposite of an A record.
Gmail, Microsoft 365, and Yahoo check reverse DNS before accepting mail. A missing or mismatched PTR is a leading cause of rejected email.
PTR records are set by whoever owns the IP block, usually your hosting provider or ISP. To add or update one, contact your provider.
Forward-confirmed reverse DNS means the PTR hostname resolves back to the original IP. Both directions must agree for full trust.
Reverse DNS resolves an IP address to a hostname, using PTR records in the special in-addr.arpa and ip6.arpa zones. Mail servers use it to identify who is connecting to them.
FCrDNS checks both directions: the IP resolves to a hostname (PTR), and that hostname resolves back to the same IP (A/AAAA). When both match, receiving servers trust the identity far more.
Many major mail providers will defer or reject your email outright. If you send email from an IP, a valid PTR record aligned with your HELO hostname is effectively mandatory.
The owner of the IP block, typically your hosting provider, cloud vendor, or ISP. Most cloud providers (AWS, Google Cloud, Azure) let you set reverse DNS in their console or via a support request.
Yes, significantly. A missing PTR, a generic hostname (like 1-2-3-4.provider.net), or an FCrDNS mismatch are all signals spam filters weigh heavily against you.
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SenderSignal monitors these signals continuously: 48 blacklists, SPF, DKIM, DMARC, TLS and more, with alerts in Slack, email and signed webhooks.