554: no 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.
- Comcast
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 554
- Provider
- Comcast (Xfinity)
- 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 PTR lookup failure
What it means
Xfinity requires every sending mail server IP address to have a valid PTR record, the reverse DNS entry that maps the address to a host name. This 554 means the lookup came back NXDOMAIN: an authoritative server for that part of the in-addr.arpa tree answered that the IP has no PTR record. The temporary 421 reverse DNS failure comes from DNS servers that do not answer properly; this one is a definite answer, so the error stays until the record is created. PTR records are set by whoever controls the IP address block, usually a hosting provider or ISP.
Common causes
- No PTR record was ever created for the sending IP.
- The server sends from a new IP, or one the provider never configured.
- The reverse zone exists but has no entry for this address.
How to fix it
- 01Look up the PTR record for your sending IP to confirm it is missing.
- 02Ask your hosting provider or ISP to create a PTR record with a name on your domain that identifies the mail server.
- 03Make sure that name resolves back to the same IP with an A record.
- 04Send again once the PTR record is visible.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 421Reverse DNS lookup failed.Xfinity could not complete a reverse DNS lookup for your sending IP. It treats this as temporary, so your server should retry, but a broken DNS setup keeps it failing.
- ES000010Dynamic or residential IP address.Xfinity blocked the connection because your server sends from IP space it considers dynamic or residential, in most cases because the reverse DNS name does not look static.
- 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.
- 554Rejected for breaking GMX guidelines.GMX refused the message permanently because the connection broke its guidelines. GMX points to its requirements page and asks for the full error message if the problem continues.
- 554IP address on the GMX blocklist.Your sending IP is on a blocklist that GMX manages itself, so its servers refuse the connection. GMX keeps a strict no tolerance policy toward spam.
- 554IP address on a Spamhaus blocklist.GMX refused the connection because your sending IP is listed on a Spamhaus blocklist. GMX makes no exceptions; the listing has to be removed at Spamhaus.
Further reading
All 33 Comcast codesEvery code in the wikiPaste your own bounce