Firemail should be the name of a free and privacy oriented email client wholly owned by Mozilla with a web and mobile app. I would sign up instantly and gradually migrate from gmail, while being assured for its sustainability.
“Free”. Therein lies the Mozilla problem. Everyone wants everything free.
It’s real hard to compete with Google who happily gives out free email and browser because they can monetize attention.
A free and privacy-oriented hosted service that people have to pay to maintain? That is a confusing concept. How would the incentives be aligned?
Maybe not exactly what you’re looking for but Thunderbird is working on a paid email service: https://www.tb.pro/en-US/