email when agent offline?

How do I set this monitor to email me whenever an agent goes offline? The only thing I need this monitor for is so I could get an email, since I only have one 24/7 server running and no other client to check and make sure it's running. When an agent is offline, it defaults to "NO DATA" instead of an error, so I never get the email, even though I have it set to email me for all alert types.