The vast majority of students and professionals will not be able to choose their school/work email provider, and the vast majority of them will want their email and calendar to be visible in the same app. That isn't possible in Proton Calendar, though, at least without forwarding all of your mail to a ProtonMail address, which may not be possible for some users, and which is a pain for the rest. As a result, very few people in that bucket are going to use Proton Calendar even if they use ProtonMail for their personal email. Maybe you'll get a few retirees and serious privacy wonks, but you'll miss the normies.
The solution is interoperability with other mail clients, and you can only do that via widely accepted standards. CalDAV support is therefore essential for this app.
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The vast majority of students and professionals will not be able to choose their school/work email provider, and the vast majority of them will want their email and calendar to be visible in the same app. That isn't possible in Proton Calendar, though, at least without forwarding all of your mail to a ProtonMail address, which may not be possible for some users, and which is a pain for the rest. As a result, very few people in that bucket are going to use Proton Calendar even if they use ProtonMail for their personal email. Maybe you'll get a few retirees and serious privacy wonks, but you'll miss the normies.
The solution is interoperability with other mail clients, and you can only do that via widely accepted standards. CalDAV support is therefore essential for this app.