Q. Why does my Microsoft Exchange Server system show the state of some links as unavailable even though the links have periods of activity?

A. Exchange Server 2003 and Exchange 2000 Server provide link-state detection, which monitors the status of the connections between routing groups. However, the link-state detection feature can sometimes cause link connectors to be marked as unavailable. I've seen this problem occur with Exchange Server systems that were connected over a DSL line: When many messages in the Exchange Server network were queued up, the link state would detect the link between the routing groups as unavailable and take it down. You can disable the link-state-change process by modifying the registry on the Exchange Server system, as follows: