FCrDNS Checker
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Validate forward-confirmed reverse DNS for a sending IP and see exactly why it passes, fails, or warns.
Frequently Asked Questions
- What is FCrDNS?
- FCrDNS means an IP address has a PTR hostname and that hostname resolves forward (A/AAAA) back to the same IP.
- Can I start with a hostname instead of an IP?
- Yes. This tool resolves hostname A/AAAA answers, then runs FCrDNS per candidate IP. Because hostnames can be load-balanced, validate the IP seen in SMTP logs or Received headers.
- Why does FCrDNS matter for email deliverability?
- Mailbox providers use reverse and forward DNS consistency as a sender identity signal. Missing or mismatched records can increase filtering risk.
- Does this tool test SMTP banner or EHLO alignment?
- No. This release is DNS-only and focuses on PTR and forward A/AAAA confirmation.