See Attendee Changes Made Through the API on Microsoft® Calendars
Where: This change applies to Lightning Experience, Salesforce Classic, and all versions of the mobile app in Professional, Enterprise, Performance, Unlimited, and Developer editions.
How: Attendee statuses sync from Exchange to Salesforce, but not from Salesforce to Exchange. Be wary of creating API flows that update attendee status in Salesforce for users set up to sync both ways. Eventually the original Exchange status overrides the update made in Salesforce.