A new PowerShell command has been made available on Exchange Online only.
This command allows you to cancel all future events (meetings) for a mailbox (user or resource).
This will automatically cancel the invitation to all attendees; this can be quite helpful when somebody leaves the company and did not cancel the meetings (especially the recurring ones).
You can go to https://technet.microsoft.com/library/mt784593.aspx to learn more about the command
Enjoy