We have an external user that's joined an O365 domain we administrate. We have been asked to remove the ability for this user to see any calendar, what so ever.
Through further investigation, we have determined the only way this would be possible would be to completely remove this users access to the calendar functionality of Outlook.
Can this actually be done?
Afaik no. You can remove the Calendar pane from OWA, but not from Outlook (either desktop or mobile).