What groupware provider is suggested for full Kontact functionality?

I enjoy using KDE’s groupware software, Kontact but I noticed that I don’t get full functionality with accounts such as Google and Microsoft. Some examples are the “journal” feature in KOrganizer, cloud task management in an app like Zanshin, and the encrypted mail functionality in KMail.
What groupware provider did the devs have in mind for maximum functionality with all Kontact features?