Consider the following scenario:
You have two Exchange organizations in a Microsoft Exchange Server 2010 environment. Email messages can be routed between these two Exchange organizations.
You create a resource in one Exchange organization, and then you set the resource to AutoAccept.
You submit a meeting request from the other organization to book this resource.
In this scenario, the meeting request is deleted, and the calendar item stays tentative in the resource.
Note The expected behavior is that the meeting request is accepted.
This issue occurs because the ResourceBookingProcessing function ignores booking requests when the requestor cannot be found in the Active Directory domain.
To work around this issue, create a contact, and then have the contact submit a meeting request by using an authenticated connection.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.