Protonmail provide encrypted email. Bridge is a Win/Mac/Linux app developed by Protonmail to allow the encrypted email account to be used with local email clients, like Thunderbird or MS Outlook.
Paid • Proprietary
What is 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.