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