554: relay access denied
Fastmail refused to pass your message on because your mail program did not sign in to the outgoing server. Turn on authenticated SMTP.
- Fastmail
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 554
- Provider
- Fastmail
- 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 Relay access denied
What it means
An outgoing mail server only relays mail to other domains for users who have signed in, otherwise anyone could send through it. When Fastmail answers with 554 Relay access denied, it usually means your mail program is not using authenticated SMTP. Fastmail points to its client setup instructions: check that the outgoing server in your mail program is set to sign in, with the details those instructions give. Once the program signs in, mail is accepted.
Common causes
- The outgoing server settings in your mail program have authentication turned off.
- The program is set to the wrong outgoing server or port.
- A device or app was set up by hand and missed the authentication setting.
How to fix it
- 01Open the outgoing (SMTP) server settings of your mail program.
- 02Turn on authentication and enter the sign-in details from Fastmail setup instructions for your program.
- 03Compare server, port and encryption with Fastmail's setup instructions, then send again.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Undelivered email (Fastmail help center)fastmail.help
Related codes
- 535 5.7.8Authentication failed for an external address.Fastmail could not sign in to the outgoing server of an external address you send from, most often because its stored password has changed.
- 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.
- 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.
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