If you have created a room mailbox, and want to create appointments directly in the calendar of the room mailbox, then you need to:

1. Enable the user in Active Directory
2. Set the password of the user
3. Log on to a workstation with that user
4. Start Outlook
5. On the Tools menu, click Options, and then click Calendar Options.
6. Under Advanced options, click Resource Scheduling.
7. Select the Automatically accept meeting requests and process cancellations check box.
8. You can then select the following options:
   • Automatically decline conflicting meeting requests
   • Automatically decline recurring meeting requests

Then it will not automatic delete calendar appointments anymore.