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FCrDNS Forward-confirmed checks
Useful Mail deliverability friendly
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Why teams use this PTR checker

Catch reverse DNS gaps before they hurt deliverability or reputation

Validate mail server PTRs

Gmail, Outlook, Yahoo and most filters require valid PTRs to accept mail. Confirm rDNS before launching email campaigns.

FCrDNS in one click

We resolve the PTR hostname forward and confirm it points back to the original IP, so you do not have to chain commands.

Inspect arpa zones

See the actual in-addr.arpa or ip6.arpa zone, plus the authoritative nameservers and SOA controlling reverse DNS.

Reverse IP lookup for domains

Enter a domain and we resolve A and AAAA records first, then run reverse DNS on every IP automatically.

Identify hosting providers

The PTR hostname often reveals the hosting provider, datacenter, or ISP behind an IP, useful for audits and incident response.

Built for ops and support

Clean output with status pills, perfect for sharing with hosting vendors when you ask them to set or fix rDNS.

When this PTR checker helps most

  • Outgoing mail is rejected with "no PTR" or "client host rejected"
  • Setting up a new dedicated server or cloud VM for sending email
  • Migrating IPs and verifying rDNS is updated everywhere
  • Auditing client infrastructure for SPF/DKIM/DMARC alignment
  • Investigating abuse, scraping, or malicious traffic from an IP

What makes this tool more useful than dig -x

  • Accepts both IPv4 and IPv6 addresses, plus domains
  • Performs FCrDNS validation automatically
  • Shows the exact in-addr.arpa or ip6.arpa zone string
  • Surfaces the authoritative NS and SOA controlling rDNS
  • Free, instant, and works for any public IP

How it works

Reverse DNS validation in three steps

01

Resolve target IPs

If you enter a domain we resolve A and AAAA records first. If you enter an IP we use it directly.

02

Query the arpa zone

We build the correct in-addr.arpa (IPv4) or ip6.arpa (IPv6) zone and fetch every PTR record returned.

03

Validate FCrDNS

The PTR hostname is forward-resolved back to its IP. If it matches, the PTR is FCrDNS-valid and trusted by mail receivers.

Note: rDNS is set by the owner of the IP block (your hosting provider or ISP), not your DNS provider. To change a PTR, open a ticket with whoever issued the IP.

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FAQ

A PTR record is a DNS pointer record that maps an IP address to a hostname. It powers reverse DNS lookups and is required by major mail receivers like Gmail and Outlook for email deliverability.

FCrDNS (Forward-confirmed reverse DNS) means the PTR hostname forward-resolves back to the original IP. Many anti-spam systems require FCrDNS to accept mail.

For IPv4, the octets are reversed and queried under in-addr.arpa (for example 4.4.8.8.in-addr.arpa for 8.8.4.4). For IPv6, hex nibbles are reversed under ip6.arpa. The PTR record returned is the hostname assigned to that IP.

PTR records are managed by whoever owns the IP block, usually the hosting provider or ISP. Contact them and ask them to set rDNS for your IP. Without it, your outgoing mail will likely be rejected.

Technically yes, but it is best practice to keep one PTR per IP. Multiple PTRs can confuse mail receivers and complicate FCrDNS validation.

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