To bill guests, a Termination Report is run for each mailbox. This report can be run either before or after the mailbox is checked out, but the results will vary.
If the Termination Report is run before the mailbox is checked out and there are unplayed messages, the system does not charge for disk usage for these messages because this resource is calculated after messages are deleted.
If the Termination Report is run after the mailbox is checked out, the system charges for all messages because all messages must be deleted in order to check out the mailbox.