I use ProtonMail mix of normal domains and my own personal ones. Never had an issue.

Email as a whole is not designed well, it can't really be private by design and it's mostly used because of people's dependence on it. Secure email services are just services that respect your privacy more than actually give them, because the privacy features are opt-in and provider exclusive, therefore they often need to be used by both the sender and receiver which is unlikely.

Use a solid service like ProtonMail or Tutanota. You could host your own but then you'd need to be totally responsible for it and choose a right hosting provider. Posteo is also good, very transparent and has the best privacy for signup I've seen, but they lack a DMARC policy for some dumb reason.