Proton Mail is an email service from Proton AG, founded in 2014 by scientists who met at CERN. It is based in Geneva, Switzerland.
Messages are stored with end-to-end encryption, so Proton cannot read them. Mail between Proton users is encrypted automatically, and password protected messages can be sent to anyone. The same account covers Proton Calendar, Proton Drive and, on paid plans, Proton VPN and Proton Pass. Hide-my-email aliases keep the real address private when signing up for sites.
The free plan has a small storage limit. Paid plans add storage, custom domains and more addresses.