If you are trying to setup your custom SMTP server settings within ServiceBox and receive same error when trying to test message Error: The SMTP server requires a secure connection or the client was not authenticated. The server response was 5.7.0 authentication required.
Please verify if you have enabled two-factor authentication on your Google account, you may need to generate an App Password to use with your SMTP server instead of your regular Google account password. Here are the steps to check if you have two-factor authentication enabled:

1.Log in to your Google Account at https://www.google.com/
2.Click on the "Security" tab on the left-hand side of the screen.
3.Look for the "2-Step Verification" section. If it says "On," then two-factor authentication is enabled.
4.If you see the "2-Step Verification" section, you can also click on it to manage your two-factor authentication settings.
If you have two-factor authentication enabled, you will need to generate an App Password to use with your SMTP server. Here are the steps to generate an App Password:

1.Log in to your Google Account at https://www.google.com/
2.Click on the "Security" tab on the left-hand side of the screen.
3.Look for the "App Passwords" section.
4.Click on "Select app" and choose "Mail" from the dropdown menu.
5.Click on "Select device" and choose "Other" from the dropdown menu.
6.Enter a name for the App Password (e.g., "SMTP server").
7.Click on "Generate."
Google will generate a 16-digit code. Use this code as your password when configuring your SMTP server settings.
Once you have generated the App Password, use it instead of your regular Google account password when configuring your SMTP server settings.