A component of Microsoft Exchange Server that verifies the state of a connection between Exchange servers and foreign mail systems. Link Monitors determine whether the messaging link to another mail system is functioning correctly. You should configure Link Monitors for all your connections to remote mail systems from your Exchange organization.
The system attendant service sends test messages between the Exchange servers and the foreign mail system at every polling interval and measures the round-trip messaging time.
Link Monitor messages are simply ordinary e-mail messages that the system attendant sends automatically at regular intervals. When a messaging link fails, the Link Monitor can perform a series of escalating actions that can include sending an alert, sending an e-mail notification, or activating a pager.
Graphic L-11. Monitoring a link.