Rivals Mailbox as the best email app on android/the planet. For me this one edges it out slightly just because it has an EAS connector and a unified inbox option.
The search functionality is a slice of perfection.
The 'cards' let you interact with other services directly from your inbox. They just added OneNote, which pushed this to the top of my "essential apps" list.
I think once they get the cards piece tuned up a bit, anybody who doesn't use CloudMagic will be looked down upon as a lesser being.