Though Teem has historically supported either impersonation or delegate access permissions for our Exchange customers, recent changes to the Office 365 platform have shifted our recommendation for Office 365 customers. In order to ensure reliable sync with Office 365, Teem recommends using Impersonation, rather than Delegate Access. For security-minded customers, we recommend limiting the scope of impersonation to conference rooms only, which allows Teem to function normally.
Note: The End Event Early function still requires complete impersonation access to all mailboxes.
The issue itself, in most cases, relates to throttling limits placed on the EWSMaxSubscriptions parameter, preventing Teem from syncing new events or being alerted when events are created or changed, leading to some events not appearing on EventBoard displays as expected.
For security reasons, Microsoft does not publish the current throttling limits nor are they able to be changed by an Office 365 admin user. For that reason, Microsoft has recommended Impersonation for this type of access to Office 365, and Teem echoes that recommendation.