X-notifier is a Firefox plugin that alerts you to new email arrivals in multiple webmail accounts. The plugin already works with many popular webmail services. For new email services, an additional script must be made.

This is the X-notifier Firefox plugin page: https://addons.mozilla.org/en-US/firefox/addon/xnotifier/

This is the current list of addon scripts: http://xnotifier.tobwithu.com/scripts.php

This is the request page for a ProtonMail script to be added to X-notifier: http://xnotifier.tobwithu.com/dp/node/3407

Could ProtonMail staff collaborate on creating a script?

Or could someone reading this with the ability to create scripts help make one to add functionality for ProtonMail?

This would also help those interested in using multiple ProtonMail accounts, as X-notiifer can handle more than one account for the same email service, and will log you in automatically to the account with new mail, when requested.