federation
Protonmail should be federated.
Why has it never been discussed? It seems silly that Protonmail only works with Protonmail, there should be a open federated standard all encrypted email providers can use together.
In a perfect world, you could use easy automated encryption between providers like Protonmail, Tutanota and Mailpile. You would even be able to easily host your own email server that adheres to this standard.
Please make it happen.

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Jan Korous commented
Maybe this idea has more chances as a grass-root road to encrypted e-mail than waiting for IETF or any other standard body to come up with that.
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Jakub-Abayomi Tsimbukondo commented
Please make ProtonMail compatible with Mailpile. Thanks
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[Deleted User] commented
So, you would have an MTA, for example, that could be configured to use, for example, the Protonmail server model and that model, with the appropriate modules, could work seemlessley with Tutanota or Mailpile - ? I like the idea, but, having worked with, and installed, MTAs myself, I could also see a lot of potential for cross-module vulnerabilities or attacks on the underlying MTA granting elevated privilege attacks, MiTM style interceptions, and malicious redirectioning, amongst others; not to mention the potential for underming the security of the standalone services themselves.