I would say that there is 3 important points to your question: 1: Use your own domain, this allows you to somewhat easily move providers. 2: Offline backup of

I would say that there is 3 important points to your question: 1: Use your own domain, this allows you to somewhat easily move providers. 2: Offline backup of your email. Keep a offline backup of you email, it could just be a desktop client checking email. 3: A paid provider with support, so you can get to talk to someone. I personally think icloud is a option. Fastmail or hey.com could also be.