I've recently migrated from Exchange 2010 to 2016. I have a few users that access many other users calendars for scheduling. I'm getting a TooManyObjectsOpenedException and MapiExceptionSessionLimit in the MAPI Client Access logs, on the client, MS Outlook, they are getting various issues, like disconnecting and slow updates to calendar updates, I'm sure this is because of this error, I'm using MAPI over HTTP and I can't find anywhere in the Throttling policy how to allow more connections or make it unlimited to prevent this. I have already changed the RPC limit for these users to unlimited. Does anyone know how to increase the limits on this?