How can one detect changes to all Microsoft Exchange 2007 users' calendars?
For single users or small groups, you can register push/pull event subscriptions. However, if you have many users (30k+), this seems unfeasible as you have to keep up with user additions, expiring notification subscriptions.
COM+ event sinks can be registered on a store-wide basis, and thus receive events for all calendars, but event sinks are deemphasized in Exchange 2007 and 2010.
What is the best way of keeping up with calendar changes for all users in newer Exchange versions?