A clean power user email app

There are tons of great email clients out there. Spark, Outlook, Gmail, Inbox (RIP) to name a few. Each of them has great standout features, and they have a lot to learn from each other. What would an email app look like that brought together the best parts of each of them - for power users?

After interviewing some power users, this is what I came up with based on their pain points and wants.

Feature request: Visibility (currently overwhelming)
Solution: Smart bundled inline categories

Feature request: Quick integrated calendar access.
Solution: Nav bar containing calendar with other essential pages.

Feature request: Easy access to attachments.
Solution: Nav bar page that allows for "files" that allow you to view recent attachments and saved contacts.