Fix “Forward-Confirmed Reverse DNS missing” errors

Q: Why does FCrDNS fail?

The three usual failures: the IP has no PTR record at all; the PTR points to a hostname that has no A record or points elsewhere; or the forward and reverse names simply don’t match. Many strict mail systems — and most banks and enterprises — require FCrDNS and reject mail that fails it.

Quick answer

If a mail server rejects your messages with a complaint about FCrDNS — Forward-Confirmed Reverse DNS — it means your IP’s forward and reverse DNS don’t match up. It’s a common, fixable deliverability blocker. Here’s what it is and how to resolve it.

What does FCrDNS actually require?

Forward-Confirmed Reverse DNS is a matching round trip. Your IP’s PTR record must point to a hostname, and that hostname’s A record must point back to the same IP. For example: IP 203.0.113.45 → PTR says mail.example.com → A record of mail.example.com says 203.0.113.45. When the loop closes, FCrDNS passes.

Why does FCrDNS fail?

The three usual failures: the IP has no PTR record at all; the PTR points to a hostname that has no A record or points elsewhere; or the forward and reverse names simply don’t match. Many strict mail systems — and most banks and enterprises — require FCrDNS and reject mail that fails it.

Step 1: Diagnose the current state

Check the reverse direction first with our Reverse DNS tool — what hostname does your IP resolve to? Then check the forward direction: does that hostname’s A record resolve back to your IP? If either is missing or mismatched, you’ve found the break.

Step 2: Fix the forward (A) record

This part is in your own DNS. Create an A record for your mail hostname (e.g. mail.example.com) pointing to your server’s IP. You control this directly through your domain’s DNS settings.

Step 3: Fix the reverse (PTR) record

This part is not in your DNS — the PTR is controlled by whoever owns the IP. Ask your hosting provider or ISP to set the PTR for your IP to the same hostname (mail.example.com). Most cloud panels let you do this yourself; see configuring a PTR record in your hosting panel.

Step 4: Verify and wait for propagation

Once both records exist and match, re-check both directions. DNS changes — especially PTR updates — can take hours to propagate globally, so don’t expect instant results. Once it confirms, the FCrDNS rejection stops.