The EnableDirectBooking registry value isn't used by Outlook 2013
Original KB number: 2788235
Symptoms
When you send a meeting request in Microsoft Outlook 2013 to a mailbox that's configured for direct booking, the meeting is not successfully booked. You don't receive an error message in this scenario. Additionally, if you open the mailbox that's configured for direct booking, the meeting request is in the Inbox folder.
This problem occurs even if you configure the EnableDirectBooking registry value on the Outlook 2013 client by using the following registry data:
Key: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Options\Calendar
or
Key: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\Outlook\Options\Calendar
DWORD: EnableDirectBooking
Value: 1
Cause
This problem occurs because the direct booking feature is completely removed from Outlook 2013. Additionally, the EnableDirectBooking registry that is available in Outlook 2010 is ignored in Outlook 2013.
Resolution
To resolve this problem, convert the resource mailbox to an Exchange resource mailbox. The following article for Exchange Server 2007 explains how to migrate a direct booking resource mailbox to an Exchange resource mailbox configured to automatically accept meetings.
How to Upgrade Outlook Direct Booking Resource Mailboxes to Exchange 2007
Similar steps can be used for later versions of Exchange. The main difference between Exchange Server 2007 and later versions of Exchange is in the cmdlet used to configure the Exchange resource mailbox. The following article contains information on how to configure an Exchange 2010 resource mailbox.
Managing Resource Mailboxes and Scheduling
More information
The following article contains the full Office 2013 feature deprecation list.