ProtonMail

Proton Mail is an application that lets users access a secure email environment in their web browser. The Swedish service allows both individuals and companies to secure all of their online communications using enhanced 256-bit encryption.

The application is primarily meant for Android mobile users; however, it is also available on the web and for iOS devices.

Since Proton Mail is incorporated in Switzerland, all of its servers are protected under rigorous Swiss privacy law. Moreover, all emails are automatically secured with end-to-end encryption: even the makers of app are unable to decrypt and read your secure messages.

Technically, it's impossible for the emails to be shared with third parties. No personal information is needed to create your email account, especially since the app creators don't keep any IP address logs linked to your account.

Basic Proton Mail accounts are always free and the code is even fully available on GitHub. This totally open-source application provides an easy way to secure your online communications.