Since Mailbox has been gutted and canned by Dropbox, I've been on a search for new email clients. Currently, I'm trying out N1 by Nylas. So far, it's been light, clever, and beautiful.
Pros: - Easy, modern onboarding - Light/Dark Toggling - Good user-interface, aesthetically. - Integrates Gmail shortcuts. - Open source - View toggles for customization - Plugin friendly - Customizable Shortcuts
Cons: - Takes a bit of time to load, initially. - Requires toggling between emails, instead of having a centralized mailbox, with "by-email" filters. - No "Later" filter, like on Mailbox. This helps a lot for Inbox Zero/Using your inbox as a To-Do list.