Docs Error Library Authentication Errors Error: SMTP Error 550

Error: SMTP Error 550

What Is Causing This Error?

Error 550 often appears when there is an issue with the client’s email server and not your SMTP plugin. It usually indicates missing authentication or an unavailable mailbox.

This error can come in different forms, and the causes vary depending on the exact error. Below are some of the most common variants of this error.

  • ‘550 Requested action not taken: mailbox unavailable’ indicates the recipients’ email address was unreachable by your SMTP server.
  • ‘Relay not permitted’ indicates missing authentication from the recipients’ email client.
  • ‘550 Blocked error’ indicates the user’s email client has blacklisted your domain or email address.

This tutorial will cover how to troubleshoot each of them.

Resolving the Error – Solution

To fix this error, you’ll need to review the complete error code. In most cases, the steps to troubleshoot the error vary depending on the exact error you see.

550 Requested action not taken: mailbox unavailable

This can occur due to a misspelled email address or incorrect recipient email. So, the first line of action is to confirm that you have the correct email address.

It can also be a temporal outage of the client email server. In this case, retrying after a while should fix your site’s email issues.

However, if the error persists, you may need to ask the user for a different email address. Since this error usually occurs due to an incorrect email address, using a valid one often resolves the error.

550 Relay not permitted

When sending an email on your website, your SMTP server needs to interact with the client email server. If the client doesn’t have the required authentication, you’ll likely encounter the ‘550 relay not permitted’ error.

This can be a temporal error and may be fixed if you wait and retry later. However, if it persists, it is likely an issue with the users’ email client and not your SMTP plugin.

In this case, the email recipient would need to confirm that their email client is configured correctly to receive emails.

550 Blocked error

Some email clients block requests from SMTP servers if they are perceived as spam. You may need to check with the email recipient to remove your domain from their blocklist.

However, if it’s happening for multiple users, your SMTP server may be blacklisted. In this case, we suggest switching to a more reliable email service provider such as SendLayer.

That’s it! Now you know how to troubleshoot and fix error 550.

If you’d like to learn how to use SendLayer to send emails on your website, check out the following tutorials: