Number of IM messages blocked per second in critical archiving mode due to local Storage Service health and connectivity issues.
This can occur due to server overload, Storage Service connectivity issues, or internal errors.
The server will continue to block messages for compliance purposes until the root cause is
of the issue is resolved. Typically, this situation occurs due to server overload and an inability
to enqueue items into Storage Service. Looking for error events from the
Storage Service will provide a good start to the investigation. Taking this
server out of rotation might be necessary to prevent further blocking of messages.