How to resolve and prevent 554 5.7.1 : Relay access denied email errors in Linux and Windows mail servers

‘554 5.7.1: Relay access denied’ error means that either the sender has failed security checks or the recipient’s mail server is misconfigured.

What causes Relay Access Denied Error?

When a mail is sent, it first goes to the sender’s mail server (aka MX). Then it’s RELAYED to the recipient’s MX, and from there to the recipient.

Here, TWO servers are involved – Sender’s MX and Recipient’s MX. If either one of these servers rejects the mail, a Relay Access Denied error is shown to the sender.

Case 1 – Sender’s MX rejects the mail

Every mail server requires its users to provide a username and password to send emails. This is to keep spammers out. But very often valid mail users forget to turn on authentication in their mail clients, and the MX rejects their mail.

Case 2 – Recipient’s MX rejects the mail

The recipient’s mail server will accept a mail only if it can verify that the recipient is a valid user in that server. For eg., if the recipient’s account is canceled or inactive, it won’t accept the mail.

The origin of these errors are:

• Improper sender MX configuration (eg. SMTP auth settings disabled)
• Inactive or canceled recipient mail address
• Recipient’s DNS MX records pointing to the wrong server (often after a migration)
• Recipient’s user database errors

Two variations of this error in web hosting servers:

• 554 5.7.1 Relay Access Denied – The recipient’s mail server logs show this error when a mail is rejected.
• 454 4.7.1 Relay Access Denied – This error is seen in server logs when the recipient server is temporarily unable to accept emails. The mail delivery will be attempted again later.