ProtonMail is a secure email service and app with end-to-end message encryption. I'm not using it but I think security is rapidly becoming a business model. I expect to see the government versus citizen arms race to generate a lot of new commercial options.
Even if you're not important or scummy secure messages are valuable.1 I'm always frustrated when dealing with attorneys or accountants. They rarely have a secure file transfer service. Even when they do, it's not something I have much control over. Services like ProtonMail could be a nice, simple alternative.
ProtonMail says that their HQ is in Geneva Switzerland and that they have "zero access to user data."
By way of App Advice