proton-mail

Install command: 
brew install --cask proton-mail

Name: Proton Mail

Client for Proton Mail and Proton Calendar

https://proton.me/mail

Cask JSON API: /api/cask/proton-mail.json

Cask code: proton-mail.rb on GitHub

Current version: 1.8.1

Current version requires: macOS >= 10.15

Analytics:

Installs (30 days)
proton-mail 412
Installs (90 days)
proton-mail 1,200
Installs (365 days)
proton-mail 4,691