I've been working on designing a more intuitive UI that emphasizes user control and simplicity in email. The idea is to make email fun and not the cluttered mess that we are used to. I've built out a prototype that features smart categorization using user-defined rules in natural language, the ability to ask questions to your email with enhanced semantic search, email composition assistance, and a Spotlight for priority emails that helps you reply as quickly as you make decisions.
If anyone would be interested, let me know, and I can send early access. It'd be free, no cost, just want to get feedback from people that care about this space.