What's the best Android app for sending secure emails that protect my privacy?

Proton Mail is an Android email client designed specifically for users prioritizing privacy and security. It employs end-to-end encryption to protect message contents from being accessed by third parties, including the service provider itself. The app operates under strict Swiss privacy laws, which adds an extra layer of legal protection for user data. For individuals handling sensitive communications—such as journalists, activists, or business professionals—this ensures that emails and attachments remain confidential. Features like self-destructing messages, password-protected emails, and a no-logs policy make it suitable for real-world scenarios like sharing financial documents or private correspondence. However, some users note the absence of a 'select all' option for bulk email management, and the mandatory conversation view can be inconvenient for those preferring traditional email threading. Reviews indicate that recent updates have significantly improved performance, though initial setup may require consulting the app's guides for less tech-savvy individuals.