A.Review the application event logs.
B.Review the message tracking logs.
C.Set the Protocol logging level to Verbose on the Receive connectors and then review the protocol log files.
D.Set the Protocol logging level to Verbose on the Send connectors and then review the protocol log files.

A.From the Exchange Management Shell， run the Get-Mailbox cmdlet.
B.From the Exchange Management Shell， run the Get-MailboxStatistics cmdlet.
C.From the Exchange Management Console （EMC）， create a recipient filter.
D.From the Exchange Management Console （EMC）， view the properties of the mailbox database.