Outlook direct booking is one of the many ways in which you can handle resource mailboxes in Exchange for a full list of other methods have a look at slipstick . Knowing which mailboxes have been enabled in your Exchange Organization could be a little tricky to keep a track of if you have a large number of mailboxes. One method of finding what mailboxes are using Direct booking is by using the freebusy data on a server. How Free-Busy data works and is stored is documented on Technet and this post on the Exchange Team Blog . The Free Busy data also comes into to play with Outlook Direct booking. When a user configures direct booking via the 3 check boxes under resource scheduling in Outlook – Calendar options there are 3 Mapi properties that get set on the local freebusy object in a mailbox. (Note this is not the only thing that happens you do enable direct booking permissions are also modified on the calendar and freebusy object in the resource mailbox) Automatically accept meeting a
Pushing the Envelope in Messaging and Office 365 Development