Nylas Mail is now free
I really wanted an Email client for Linux which isn't power hungry but unfortunately last I tried Nylas - it was always top app in `powertop`. An always running app has to be low on power consumption IMO, but because so many apps are being built on top of webkit/electron most of them pretty much suck when it comes to battery usage.Another case in point is slack app. On Linux, it is probably the worst app. :(