Use exchange web services managed API to subscribe to notification when appointment has started

How can I subscribe to a notification that will trig开发者_如何学运维ger every time that an appointment has started?

This is not possible, since Exchange does care about appointments in user mailbox. For the store, it's just an element with a bunch of properties.

What you can do is create a service which checks a users mailbox, retrieves all appointments and triggers an event once an appointment has started. Additionally, you can subscribe for notifications so that your application is informed by the Exchange server when an item in the users mailbox changes.