Install checkgmail by entering the following commands in the terminal:
sudo apt update sudo apt install checkgmail
alternative Gmail Notifier for Linux via Atom feeds
CheckGmail is an alternative Gmail Notifier for Linux and other *nix systems. It is fast, secure and uses minimal bandwidth via the use of Atom feeds. . CheckGmail is a system tray application that checks a Gmail account for new mail. When new mail is present the tray icon changes, an optional animated popup is displayed and a tooltip displays the number and details of new messages. Configuration is GUI-based and the application is designed to be simple, elegant and unobtrusive.