What is the crowd's opinion of Zanshin?
From 3.5 billion comments

➔ Zanshin website

By popularity online, this Service is:

#127 in Todo List apps

1 review of this app found across the web:

While I'm currently using Outlook via Office365, as of now I know the mail server itself isn't an Exchange server.

> Using KOrganizer? All your overdue and coming task will appear in the calendar view.

From Zanshin's feature page sounds promising. I may start looking more in Korganizer if Zanshin is working with it as I'd like.