ProtonMail is a Swiss e-mail service billed as being secure and encrypted. It was launched by a number of people who worked at CERN.
ProtonMail is on Marginalie's Software watchlist. Though it is possible to sympathise with those who say that e-mail, being an old and now outdated protocol, is broken, there are strong arguments for improving accessible email services, and ProtonMail appears to be one to watch in this area. Marginálie could not endorse such a service, however, until it works with PGP. It is not currently encouraging that krozruch has tried to comment on the page dedicated to questions about PGP and it has not been added, indeed, that no such comment has been added since 2016. This despite that fact that PGP has long been on the list of future features. Indeed, it is not possible to log into the questions pages.
Despite its problems, PGP is an essential part of the email infrastructure and any service which does not offer PGP between accounts irrespective of where they are hosted cannot be considered to be serious about encryption.