Setting Up Google App

Go to https://console.cloud.google.com/apis/credentials

If you don't have one, create a new project

Go to Library and enable GMAIL Api

If you don't have it, configure the consent screen

Click Add or Remove Scopes and search gmail.send

Click on + CREATE CREDENTIALS and select OAuth client ID

Select "Web Application" as the type

On Authorized redirect URIs add your xBit installation host + /about.php (http://yourdomain.xbit/about.php for example)

Copy the Client ID and Secret

Configuring in xBit

Go to Admin -> About/Settings

Go to the E-Mail tab

Select Enable SMTP and type GMAIL

Complete ClientId and Secret

Click Submit SMTP Settings
Authorize Gmail