I created an application on my Google Cloud (https://console.cloud.google.com) for my own domain name and set client id and client Secret on config.oauth2.php. On the other hand, I installed Mail Proxy Service for Gmail Imap on my server and set "imap.gmail.com" => "localhost:1143" on config file.
When I start configuration, vTiger redirect to google, and it asks me login and password and fina