Tutanota

It provides end‑to‑end encrypted email, calendar, and contact management, using post‑quantum‑resistant cryptography to keep user data private without advertising or data mining. The service includes a zero‑knowledge calendar that stores events only for the user, and integrates encrypted invitations with the email client. Mobile apps for Android and iOS allow offline access, while a web interface offers a fast, ad‑free workflow and support for custom domain addresses.

The platform targets individuals and organizations that prioritize security and privacy in their communications, offering a free tier with core functionality and open‑source components. It emphasizes minimal data collection, renewable‑energy hosting, and a design intended to be simple and efficient for everyday use.

Distinctive aspects include the use of quantum‑safe encryption, a unified suite that combines email, calendar, and contacts under a single privacy‑focused umbrella, and the availability of open‑source code for the core services.