> The vast majority[1] of the public use Google Mail / Outlook.com[2] / Yahoo mail...

I suspect a main reason for the popularity in using these e-mail systems is because they are free - (although you do have to put up with ad's).

I see that of the services provided by Protonmail, one of their services is free. Protonmail claim to offer...

End-to-End Encryption - Automatic Email Security

All emails are secured automatically with end-to-end encryption. This means even we cannot decrypt and read your emails. As a result, your encrypted emails cannot be shared with third parties.


Easy to Use - Security without the hassle

ProtonMail can be used on any device without software install. ProtonMail secure email accounts are fully compatible with other email providers. You can send and receive emails normally.


...so maybe people will move over to using products like Protonmail for the e-mail.

cheers,
Ian.