Proton Mail Desktop App Portable

Select > Install page as app (or "Create Shortcut" and check "Open as window").

If your portable setup holds active session tokens (keeping you logged in so you don't have to type your password every time), Best Practices for a Secure Portable Setup proton mail desktop app portable

Using a desktop client (portable or otherwise) offers several privacy advantages over a browser: Decentralization Select > Install page as app (or "Create