[AccountAccount1]

I use Mailspring (previously I used Nylas Mail) just because it's what I'm used to... they do have neat features like pixel tracking (when your email is open by your recipient by sending an HTTP request to, say, an image) which is interesting.

But, to be honest, I think that the product space is not too big for email, we already communicate with so many tools that emails are left for just formal stuff (in my case) support tickets, contracts, updates, etc... there are but a few angles like privacy, but they kind of seem overcrowded (others are custom domain names, very intuitive UX, very good info about leads etc...)

I think you would have to get a really original angle, a true niche, something that has passed over everyone, and then the virality of it... I think intuitive UX is necessary but not sufficient; interested to see what you make of it, it's a good problem to solve