Error: SMTP server authentication error

What's Causing This Error

This error represents a variety of issues that would not allow the user to authenticate to the email server. Some of the most common issues include the following:

• Invalid username and password.
• Unsupported encryption.
• Unsupported authentication method.
• User account is disabled.

Solution - Here's How To Resolve It

To resolve this issue, the user can follow these steps:

1. Ensure that the username and password are valid.
2. Use an encryption algorithm supported by the email server. The email server administrator can provide additional details.
3. Use an authentication mechanism supported by the email server. Some modern email servers require modern authentication mechanisms such as OAuth 2.0.
4. Request the email server administrator to verify if the user is active.