[rekoil]

While I agree with you in general, E2EE can't be a blanket excuse for building bad applications. If your E2EE applications can't deal with data encryption in a way that makes them comparable to competitors non-E2EE products from a usability aspect, then they are still bad applications, regardless if we know that E2EE does make it all way harder.

I love Proton, but there are aspects of E2EE that they haven't worked around well enough at present, in my opinion.

The biggest pain points are:

    - Collaboration
    - Offline access

Both of those are highly relevant for calendars, so it doesn't surprise me they didn't hit the nail on the head on the first try.

[EduardoBautista]

The issue is that the open protocols IMAP, CalDAV, and CardDAV weren't built with E2EE in mind. This is the big reason why you can't use 3rd party calendar clients with Proton.

[ivan_gammel]

3rd party client or support for those protocols is not the only solution to collaboration and offline access. Their own app must do it well first.

[rekoil]

If that's the only issue it should be trivial for Proton to release a slightly modified version of Thunderbird that allows decrypting an encrypted CalDAV XML. That could then be the basis for extending the spec to allow encryption.