The Spotlight on Messaging Service Account does not have permissions to successfully connect to a Exchange organization.
The Spotlight on Messaging Service Account is not a member of the View-Only Exchange Administrators group.
The Spotlight on Messaging Service Account is not a member of the Local Administrators group on each Exchange Server.
1) Add the Spotlight On Messaging Service Account to the View-Only Exchange Administrators group
2) Ensure that the Spotlight On Messaging Service Account as a member of the Local Administrators group on each Exchange Server in the organization.