User Configuration > Administrative Templates > Microsoft Outlook 2016 > Miscellaneous > Miscellaneous
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HKCU\software\policies\microsoft\office\16.0\outlook\options\shutdown
This policy setting controls Outlook's "fast shutdown" behavior for add-ins. If you enable this policy setting, the BeginShutdown and OnDisconnection events should always be called for all add-ins. If you disable or do not configure this policy setting, all Outlook addins should always use the Addin Fast Shutdown behavior and not have the BeginShutdown and OnDisconnection events called.