Type: Configuration error (You are often able to resolve this type of error.)
Description: Impersonation of user denied. The connecting Exchange user does not have permission to impersonate the requested resource.
Possible solution: Application impersonation might not be allowed for the connecting Exchange user. Perhaps, a recipient filter that excludes the requested resource might be configured for the application impersonation role. If the error happens when connecting a service account, please make sure that the service account itself is within the impersonation scope since the validation of the service account is done by impersonating the service account itself.