ProtonMail Bridge

The ProtonMail Bridge is an application for paid users that runs on your computer in the background and seamlessly encrypts and decrypts your mail as it enters and leaves your computer. It allows for full integration of your ProtonMail account with any program that supports IMAP and SMTP such as Microsoft Outlook, Mozilla Thunderbird and Apple Mail.

Email clients such as Outlook, Apple Mail, and Thunderbird do not support encrypted email natively. However, if paired with the ProtonMail Bridge, users can continue to use their favorite email client and normal workflow while enjoying the benefits of encrypted email. The Bridge is a desktop application that serves as a translator between email clients and ProtonMail servers. In one direction, it fetches encrypted emails from ProtonMail servers, decrypts them, and sends the decrypted data to the email clients. In the other direction, it passes commands from the email clients to the ProtonMail servers, such as moving some emails to another folder or sending a new email. The Bridge will automatically encrypt certain data before sending it to ProtonMail servers.