DNS Diagnostics

DNS العكسي وFCrDNS

Check PTR records, verify forward-confirmed reverse DNS, and explain whether a mail server or outbound IP has a trustworthy reverse DNS setup.

PTR Lookup

Fetches reverse DNS hostnames directly from the resolver path.

FCrDNS Check

Confirms whether PTR hostnames resolve back to the same IP.

Operational Context

Helps explain failures that affect mail, abuse desks, and server trust.

IP Address

Examples

Use this before troubleshooting SMTP reputation, outbound relay issues, or host identity mismatches.

Enter an IPv4 or IPv6 address to inspect its PTR records and forward-confirmed reverse DNS status.

Why FCrDNS matters

Mail receivers, security tools, and abuse workflows often expect the PTR hostname to round-trip back to the same IP.

Common failure mode

A PTR may exist but point at a hostname that resolves to a different IP, usually after renumbering or DNS drift.

What “good” looks like

One intentional PTR hostname, a matching forward lookup, and a hostname pattern that reflects the server role.

حول هذه الأداة

The Reverse DNS Lookup and FCrDNS Checker helps you verify how an IP address identifies itself on the network. It performs a PTR lookup, then checks whether each returned hostname resolves back to the same IP address. That second step is known as forward-confirmed reverse DNS, or FCrDNS. It is commonly used in mail reputation checks, abuse desk workflows, relay validation, and server inventory audits. If an IP sends outbound email, hosts public services, or appears in logs you need to trust, this check gives you a fast way to confirm whether DNS identity is coherent.

كيفية الاستخدام

Enter an IPv4 or IPv6 address that you want to verify.
Run the reverse DNS check to fetch PTR hostnames.
Review the forward-confirmation panel to see whether those hostnames resolve back to the same IP.
Use the warnings section to identify missing PTR records or hostname mismatches.
Cross-check the result with your MTA, cloud IP allocation, or DNS provider if the verification fails.

الميزات

Reverse DNS lookup for IPv4 and IPv6 addresses
Forward-confirmed reverse DNS verification
Mismatch detection for stale or incorrect PTR hostnames
Human-readable verdicts for mail and operations teams
Landing-page style explanations for SEO and educational use

حالات الاستخدام الشائعة

Checking outbound SMTP relay identity before production rollout
Auditing cloud instances after IP renumbering
Troubleshooting spam filtering or poor mail reputation
Validating provider-managed PTR delegation
Explaining host identity during incident response or abuse review

التفاصيل التقنية

Reverse DNS stores hostnames in PTR records under reverse-mapping zones such as in-addr.arpa for IPv4 and ip6.arpa for IPv6.

Forward-confirmed reverse DNS means:

The IP resolves to one or more PTR hostnames.
Those hostnames resolve forward with A or AAAA lookups.
At least one forward address matches the original IP.

This check does not prove trust by itself, but it is a widely used hygiene signal in mail systems, abuse processing, and infrastructure operations.

Reverse DNS FAQ

What is the difference between reverse DNS and FCrDNS?

Reverse DNS only asks for PTR records. FCrDNS goes one step further and checks whether the returned hostname resolves back to the same IP address.

Does a missing PTR always break mail delivery?

Not always, but it often hurts reputation and can trigger stricter filtering. Many receivers expect outbound mail IPs to have sensible reverse DNS.

Can one IP have multiple PTR records?

Yes. It is allowed, but multiple PTRs should be intentional because they can confuse identity-based checks and operational debugging.

Why can PTR exist while forward confirmation fails?

The hostname may have been moved, deleted, or updated incorrectly. Reverse and forward DNS often drift apart during migrations or IP reassignments.

Related DNS Tools

استعلام DNS

استعلام سجلات A وAAAA وMX وNS وTXT.

مولد PTR

in-addr.arpa/ip6.arpa.

مدقق السجلات

A/AAAA/CNAME/MX/TXT/SRV.