Recs.
Updated
SpecsUpdate
Pros
Pro Extensible
Currently there are plugins for GitHub integration, Templates, and Translation, and the potential for many more to come. It's built on top of Chromium so making plugins for it will not only be easy for Chrome app and extension developers, but it means that it has the potential to use Chrome plugins, too.
Pro Works with Exchange accounts
N1 is one of the few 10 Windows Desktop Clients to offer support for a business Exchange email account (the Windows Native Client is one of the few alternatives that also work). It seems that this niche is really dominated by Outlook, and few solutions are available that prioritize it.
Cons
Con Not suported anymore.
I heard the development/updates on NylasMail has stopped. It stopped working for me on my Mac all of a sudden. It gave a certificate error on email accounts I had setup on my phone and iPad as well. No errors there. I wasnt getting any new mail in either. Had to delete the program and move to Mailspring which is Nylas Mail but improved and continued.