In order to use the Gmail platform for email delivery, you need to create a GSuite account (https://suiteguides.com/how-to-create-a-gsuite-account/ )
Under In the Settings → Integration → Email Notification section, use the following settings
...
Service: Custom SMTP server
From address: Your company email address
From name: The name to be used in notifications
Login: Login of your GSuite account
Password: Password of your GSuite account
Enable SSL checkbox: Enabled
Host: smtp.gmail.com
Port: 465