This is not an email client, but an end-to-end service with clients controlling everything. That’s an immediate no for me. I have multiple email domains hosted by different providers (including myself), they can’t be merged, and I’m not gonna let a single company (Big Tech or not) cannibalize everything anyway. I’m also not gonna use different clients for different domains on each platform (unless work mandates something, in which case I’ll single out work).

Oh, and they don’t support custom domains at the moment.

Some features seem nice though.