554: forward-confirmed reverse DNS failed
GMX refused the connection because the name in your IP address PTR record does not resolve back to that same IP, so the FCrDNS check failed.
- GMX, WEB.DE
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 554
- Provider
- GMX, WEB.DE and mail.com
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
554 FCrDNS check failed
What it means
Forward-confirmed reverse DNS (FCrDNS) is a two-way check. GMX takes the PTR name of your sending IP, looks that name up in DNS, and expects to get the same IP back. Case r0603 means none of the PTR names for your IP resolves to it: the name may have no A or AAAA record, or point elsewhere. GMX refuses the connection with 554. The case page refers to RFC 1912 for DNS setup and says delivery works again as soon as the corrected records are published and the check passes.
Common causes
- The PTR name has no A or AAAA record.
- The A record of the PTR name points to a different IP, for example after a server move.
- The PTR was set to a name in a domain you no longer control.
How to fix it
- 01Look up the PTR record of your sending IP, then look up the A or AAAA record of that name.
- 02Add or correct the A or AAAA record so the name returns your sending IP.
- 03Wait for the change to propagate, then let the server retry.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- GMX Postmaster case r0603: 554 FCrDNS check failedpostmaster.gmx.net
Related codes
- 554Reverse DNS does not meet GMX requirements.GMX refused the connection because the reverse DNS (PTR) record of your IP looks generic or dynamic. GMX expects a fixed IP with its own mail host name.
- 554No reverse DNS for your IP.GMX refused the connection because the IP address of your mail server has no PTR record, so it is not tied to any domain name in DNS.
- 554Transaction failed.The server permanently refused the transaction, often after receiving the message data or straight away when the connection opened.
554 at other providers
- 554Permanent rejection (554).Yahoo or AOL rejected the message for good with a 554. Yahoo uses this code for several problems, from failed authentication to unacceptable content, so the wording of the reply tells you which.
- 554Failed authentication.Yahoo or AOL refused the message because it failed the checks that confirm the sending domain, such as DKIM against the domain's policy. Yahoo lists this among its permanent 553 and 554 errors.
- 554Recipient does not exist.The Yahoo or AOL account you wrote to does not exist. The failure is permanent: check the address with the recipient, and remove it from any list.
- 554No reverse DNS (PTR) record.Xfinity refused the connection because your sending IP has no PTR record. Every server sending to Xfinity needs valid reverse DNS, so the owner of the IP must add one.
- 554No reverse DNS for your IP.IONOS refused your mail because the IP address of your mail server has no domain name assigned to it in DNS (no PTR record).
- 554Reverse DNS does not meet IONOS policy.IONOS refused your mail because the PTR record of your IP does not meet its policy, typically a generic or dynamic-looking provider name.
Further reading
All 57 GMX, WEB.DE codesEvery code in the wikiPaste your own bounce