AFAIR none of those allow sending and receiving calendar invitations, that interfunction with outside services (eg Outlook.com, Gmail, Apple). Proton does. Send a calendar invitation from gmail/outlook/Apple to a Proton user; they can accept it and it will automatically add to their calendar and send back an acceptance email that gmail/etc understands. Vice-versa also true.
I trialled almost all of those before I ended with Proton, because it was the only one that felt like they actually tried to get calendar and email functionality on par with major (non-privacy focussed) service providers, and in general was the most polished.
They are all fine if literally all you need is simple email though.
AFAIR none of those allow sending and receiving calendar invitations, that interfunction with outside services (eg Outlook.com, Gmail, Apple). Proton does. Send a calendar invitation from gmail/outlook/Apple to a Proton user; they can accept it and it will automatically add to their calendar and send back an acceptance email that gmail/etc understands. Vice-versa also true.
I trialled almost all of those before I ended with Proton, because it was the only one that felt like they actually tried to get calendar and email functionality on par with major (non-privacy focussed) service providers, and in general was the most polished.
They are all fine if literally all you need is simple email though.
Thanks for the info!
Tuta does.
Source: I use Tuta as my main driver.