I should be able to use end to end encryption with Protonpass + Simplelogin for alias forwarding. I should be able to enter my Protonmail public key in SimpleLogin and have the email encrypted then forwarded to Protonmail. I can do this using Bitwarden & Addy.io SimpleLogin explicitly disables this PGP option for Proton Mail mailboxes, calling it redundant.

If SimpleLogin permitted and properly implemented user-controlled PGP encryption using your Proton Mail public key before forwarding emails to Proton Mail mailboxes (in the same manner as Addy.io currently does), the integrated Proton Pass + SimpleLogin solution would become the superior option in a high-privacy threat model.

In this hypothetical scenario, the Proton ecosystem would provide unified single-entity control under one trusted Swiss provider, handling both the alias relay and the final inbox. This would significantly reduce the overall attack surface compared to using two separate companies, as any subpoena or compromise would involve only one jurisdiction and one set of operational security practices.