Mustang
This is a new full-featured email client, chat, video conference, calendar, contacts and files app.
It is a desktop client for Linux, Windows and Mac OS X, written entirely in JavaScript and HTML. It should later run on smartphones as app as well.
It is currently based on Electron as runtime, but may be adapted to use other runtimes like Cordova and maybe Gecko as well.
It makes an emphasis on clean code architecture and design and APIs, with a strict separation between logic and UI code, and observers, to allow easy modification and adaptions to new needs. It will also support extensions, using a high-level API.
See docs/INSTALL.md and docs/