It's FOSS - https://itsfoss.com/protonmail/
Brief: Have a look at ProtonMail, a secure, privacy-focused email provider that you can use as an alternative to Gmail.
I, like most people in 2017, use email every single day. I, also like most people in 2017, have several email addresses that I manage.
The difference between most people in 2017 and myself is which email providers we use. I am going to throw out a wild guess and say you use a Gmail account as your main email address. And if you don’t I bet you know SEVERAL people that do.
And that’ an issue for a privacy-focused person