Organizers' email accounts must be on Office 365 and can access the FindTime Outlook add-in in Outlook 2013, Outlook 2016, or Outlook Web Access (OWA). The add-in can be seen on the top banner. When I accept an invitation and forget to assign it a specific calendar, default goes to Definite.
NOTE: Options include your own calendar, group calendars, and team calendars. mac calendar invite to outlook To add a delegate to your Exchange calendar: Open Outlook.
