- It's a fork of Nylas Mail with the entire mailsync codebase (~40k lines of JavaScript) replaced with a new C++ core based on Mailcore2. It uses roughly half the RAM and CPU of Nylas Mail and idles with almost zero "CPU Wakes" thanks to new C++11 features, which translates to great battery life. You might not even notice it's an Electron app.
- It still has the same great pro features, like snoozing and send later, but doesn't send your email credentials to Mailspring servers. All of these features have been re-implemented to run locally on your computer.
- The pro features still cost money ($8/mo). The goal is to use revenue from subscriptions to pay maintainers (myself, possibly other folks!) to maintain Mailspring indefinitely and/or put bounties on popular feature requests.
- The roadmap and website are still being assembled, but there's some really cool stuff in the works. Launching it and polishing the new C++ sync codebase is just step 1.