ProtonMail has set up a Tor hidden service, or onion service, to allow users to access the encrypted email service directly inside the Tor anonymity network. It is set up in such a way users don’t know the real Internet Protocol address of the server, and the server can’t see the real IP addresses of the users. Because Tor uses multiple layers of encryption, there is no way for someone monitoring a user’s internet connection to tell whether he or she is accessing Protonmail. The company has managed to obtain a certificate for its Tor address from DigiCert.”]