Verified ProtonMail. ProtonMail is the world's largest secure email service, developed by CERN and MIT scientists. We are open source and protected by Swiss privacy law. ProtonMail is the world's largest secure email service. It offers end-to-end encryption and lots of other great security features to keep your communications private. Even the company hosting your emails has no way of reading them, so you can rest assured that they can't be read by third parties either. Unlike Gmail or Outlook, email you send with ProtonMail is encrypted before it's sent to the ProtonMail servers. That means that no hacker intercepting emails sent from ProtonMail will be able to decrypt and read your emails.