In 2014, Proton Mail became the world’s first email service to protect data with end-to-end encryption, and today is the world’s most popular secure email service with millions of users worldwide. Proton Mail’s technology is often misunderstood by tech writers (and sometimes incorrectly represented in the press), so this article aims to provide a clear description of how Proton Mail’s technology is different from Gmail, and what makes Proton Mail more secure.