I will not get into the schematics of Hey as an email as service or Hey as an email client (as Nathan Baschez has dug it deeply), or the unit economics, or the business model.
I am following Jason fried for their blog for a long time now, I saw it moving from medium to their own hosted domain. I used Basecamp ten years ago. I follow Jason on Twitter, and I admire him for his clarity of thought in running businesses. When I asked, he responded.
For Hey, Design Fails = Product Fails
When I have no new email in Hey, the interface bothers me. As if it looks into my eyes in a dark white room. There is no reason for an email service interface to show it this way and in this much of space. Sorry.