Get the Whitepaper called Mail Information Gathering AppScript. This paper contains the exploitation of vulnerabilities for collecting email information using Google utilities via App Script using the Gmail App class. This paper exposes the design of a web application that collects mail information from users with associated Google mail accounts.
You can download it from the following link: https://packetstormsecurity.com/files/download/165217/mail-gathering.pdf
Source: https://packetstormsecurity.com/files/165217/Mail-Information-Gathering-AppScript.html