In some e-mail systems, certain information might be stored as resource mailboxes, whose names need to change in order to preserve things like meeting acceptance. Also, certain users who once had mailboxes may no longer be working in your organization. In both of these cases, it may be desirable to change the name of the mailbox or move its contents into a subfolder of another mailbox.
Mailbox transformation rules are an advanced feature that we use to accomplish both of these tasks.
The result is that appointments set in resource calendars will point to the correct address for the room mailbox in the target system, and that it will not be necessary to acquire additional Exchange licenses for users who are no longer needed.