Plan to set up custom domain + Proton Family for more privacy

Yes. But why? For now Proton is the most trustworthy email provider.

We have also:

  • Tuta (Tutanota) but it doesn’t support PGP (have proprietary encryption, so we have no 100% (let’s say we have 89%) guarantee that it doesn’t have backdoor) also it is located in Germany (part of 14 eyes) alliance
  • Skiff (new, have various privacy issues)