Had a customer that was having issue with exchange smtp communication going offline intermittently. The process to get it operation again was relatively quick yet as this was happen randomly once a week I needed a method of reporting faults before the user notice the issue.
I search the web and after testing a few applications I found PRTG Network Monitor. It was quick to install and get operational. I had emails send to me everytime the SMTP communication when down. This made the customer very happy as they had no real downtime while we organised a new server.
PRTG also has the option for high level monitor, not only of services state and system information but also band width usage.
See attach link for more information.