What are the things that can go wrong with your Exchange Server?  First, there are basic resources that need to be monitored to include:


CPU Utilization:  Monitor at the host and the virtual machine level and also monitor % ready to ensure your host is not too busy.
Available virtual memory:  Monitoring for this will let you know when you are about to run out of virtual memory – this can cause a lot of problems to include shutting down the Exchange server.
Disk Space: This is a critical metric to keep a watch on as problems can result in mail store corruption that can take hours to repair.
Hardware health: A problem with the hardware can cause an application failure.  Monitor key components like fan speeds, temperature, and power supply/CPU/memory status.


Monitor Exchange Performance Metrics

You also need to monitor Exchange application performance.  Here are a few of the Exchange Performance Metrics you should keep an eye on.  Monitoring Exchange server performance helps you to:


Keep mobile devices in sync. The average number of active sync requests per second allows you to verify if your mobile workforce devices, such as Windows, iPhones & Androids remain in sync with the Exchange server. 
Schedule maintenance when it’s least likely to impact users.  Monitor current connections to quickly determine the number of people using Exchange at a given time so you can schedule maintenance at the most optimal time.
Determine when the mail service is slow.  Average response time measures how long users have been waiting for information they have requested.  The slower the service, the more phone calls you will see in the help desk.
Determine if mail is actually being sent.  Messages delivered/sent per second validates that messages are actually being sent.  You can also simulate an email round trip to test the ability of your SMTP server to receive and distribute email, and the ability of your users to retrieve email through the Exchange Web Service.
Ensure security.  Monitoring mail flow will assure you that your Exchange server is not being used as a mail relay or that your users’ workstations aren’t compromised by botnets.
• Pinpoint Active Directory Issues.  Monitoring failed LDAP searches indicates there is something wrong with AD that could negatively impact Exchange.  LDAP searches time out per minute lets you know that you have an issue right away.


Monitor Critical Processes and Services

Monitor for specific Windows services to be alerted when they stop.  There are also several Microsoft Exchange services you should monitor to ensure Exchange availability.  These include the Active Directory Topology Service, File Distribution Service, IMPA4 Service, POP3 Service, and the Exchange Service Host service.  Many of these services are dependent upon one another.

When CPU or memory spikes, look at the processes that are causing high consumption of resources.

For more information on Exchange Monitoring, check out this short video or go to this on-line demo to see what can be monitored with Server & Application Monitor.