As it stands, Proton accounts messaging Proton accounts is extremely secure. Using PGP keys, Proton accounts can message non-Proton accounts and still have private emails.

Yet, Proton accounts cannot email Tuta accounts with full encryption, despite both companies supporting internal encryption.

Proton Drive is similarly affected, with the ability to share and live-edit limited to within Proton's own ecosystem.

To overcome these privacy barriers, Proton needs an open source protocol which other services can follow to share files and send emails with the same security afforded to internal Proton interactions.

Privacy online should not be limited to interactions between Proton users and Proton users, Tuta users and Tuta users, Signal users and Signal users. Rather, each and every email server (and cloud storage, be it Nextcloud, Tuta, Proton, etc.) should be able to follow a standardized protocol which allows them to join a network of security.

Everyone who joins an end-to-end encrypted service, including those who self-host, should be able to securely message every other person who has joined an end-to-end encrypted service.