Proton Mail Bridge has been open-source since April 2020. It functions as a daemon that serves as an interface between Proton Mail's encrypted email services and standard IMAP/SMTP email clients. This allows users to integrate Proton Mail with applications like Thunderbird, Outlook, and Apple Mail. The Bridge can be compiled with or without its Qt-based graphical user interface (GUI), offering flexibility for both desktop and headless environments. https://github.com/ProtonMail/proton-bridge/issues https://github.com/ProtonMail/proton-bridge/blob/master/Changelog.md https://github.com/ProtonMail/proton-bridge/wiki ProtonMail/proton-bridge