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“550 Authentication is Required for Relay” when Sending Email

When attempting to send email using Microsoft Outlook, Outlook Express, or other email client software, you may receive the message “550 Authentication is required for relay” from your mail server.

The reason for this error is that your email server is configured to require SMTP authentication to send outgoing mail, which is a way an email sender can be authorized. In order to resolve this issue you will need to configure your email client (Outlook, Outlook Express, Eudora, Thunderbird, etc.) to send using the appropriate credentials.

To solve this problem, configure your email client to use SMTP authentication. Instructions for a few email clients are shown below. The exact steps to use, however, depend on the version of software you use, so the instructions below are provided as a reference and are intended to get you headed in the right direction.

For Microsoft Outlook, do the following:

  1. Click the Tools menu in Outlook.
  2. Click Email Accounts.
  3. Click View or change existing e-mail accounts.
  4. Click Next.
  5. Highlight an email account.
  6. Click Change.
  7. Click More Settings.
  8. Click Outgoing Server tab.
  9. Check the “My outgoing server (SMTP) requires authentication” option.
  10. Make sure that Use same setting as my incoming mail server is selected.
  11. Click OK.
  12. Click Next.
  13. Click Finish.

For Outlook Express, do the following:

  1. Click the Tools menu in Outlook Express.
  2. Click Accounts.
  3. Highlight an email account and click Properties.
  4. Click the Server tab.
  5. Under the Outgoing Mail Server, check the “My server requires authentication” check box.
  6. Click the Settings button.
  7. Make sure that “Use same setting as my incoming mail server” is selected.
  8. Click OK.
  9. Click Apply.
  10. Click OK.
  11. Click Close.

For Mozilla Thunderbird, do the following:

  1. Go to Tools > Account Settings > Outgoing Server (SMTP)
  2. Select the server and press the Edit… button
  3. Check the Use name and password option
  4. Add your username. Your username should be your full email address (e.g., “”)
  5. Thunderbird will ask you for your password the first time you send mail and you can optionally save it at that time.

Other email clients have methods of configuring SMTP authentication as well. Search the help in the product you use for more information on how to configure SMTP authentication.

If you require any further assistance, please do not hesitate to contact our Support Team 24/7!

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