I have a client that recently migrated to Exchange 2013 from Exchange 2007. Shortly before the migration, I converted all their resource calendars to the Resource Booking Attendant booking method (AutomateProcessing setting is set to AutoAccept). They do not want any conflicts to be allowed, so I set the following settings on all the resource mailboxes:
AllowConflicts - False
ConflictPercentageAllowed - 0
MaximumConflictInstances - 0
I have tested and determined that these settings seem to work properly, at least for new meeting requests. However, there seem to be some scenarios in which recurring meeting requests are approved even when there are several conflicts.
After some investigation, my suspicion is that existing recurring meetings that originally had no conflicts when accepted (and likely were accepted prior to enabling the Resource Booking Attendant) are automatically accepted when the original series is modified to extend the number of recurring instances, even if the new instances are in conflict with other meetings on the calendar.
Can anyone tell me why Exchange may be allowing updates to existing recurring meetings that cause conflicts? Based on everything I've read online, the current calendar property settings noted above should be preventing this. I need to find a way to prevent this, or at least be able to explain to the client why this is happening.