550 Authentication is required for relay error when sending emails

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

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

Resolution:
To solve this problem, configure your email client to use SMTP authentication. Following are the steps to enable SMTP authentication in Microsoft Outlook and Outlook Express. The exact steps may vary depending on the version of software you use:

Microsoft Outlook:

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 My outgoing server (SMTP) requires authentication.
10. Make sure that Use same setting as my incoming mail server is selected.
11. Click OK.
12. Click Next.
13. Click Finish.

Outlook Express:

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.

Kailash Aghera