Sumatra Development leads the field of migrating entire calendar servers to Exchange. We migrate Oracle Calendar Server, Oracle Beehive, Apple iCalendar, and Zimbra to Microsoft Exchange keeping all meeting information and resource bookings intact. We migrate calendars server-to-server between Exchange and Office 365 while keeping meetings live and doing incremental syncs quicker than any other solution.
Finally Microsoft does something to fix the terminated user problem of ghost meetings.
Remove-CalendarEvents -Identity user@domain.com -CancelOrganizedMeetings -Confirm:$false -verbose
Arm yourselves with knowledge!
