The appointments that you schedule by using the Direct Booking feature can be seen by all users in the Outlook resource calendar

When you schedule an appointment by using the Direct Booking feature in Microsoft Outlook, this appointment is viewable by everyone in the Outlook resource instead of only being viewable by the appointment attendees and organizers.

When you use the Direct Booking feature to schedule an appointment, you must have Author permissions on the resource that is being booked.

Access to the Resource Mailbox Calendar so that you can open and read items in the Calendar, is allowed only if the user or group are granted Reviewer permissions or higher. Therefore, in most cases, every user of the Resource can see an appointment.

This behavior is by design.

To schedule an appointment that only Attendees and owners of the Resource account can view, mark the item as Private. To do this, follow these steps:

1.	In Outlook, open a new meeting item or an existing item where you are the Meeting Organizer in your Calendar.
2.	At the bottom right corner of the meeting item window, check the box marked Private.
3.	If this is a new item, continue to configure the item and send it to the invited Attendees or the Resource mailbox or both. If this is an existing item, click the Send Update button to send the update to the Resource mailbox and the Attendees.

This will only allow the Attendees of the appointment to open and see the contents of the item. However, anyone with full access to the Resource mailbox will be able to open the mailbox, access the Calendar and read the appointments.

For more information about the Direct Booking feature, click the following article numbers to view the articles in the Microsoft Knowledge Base: