Here’s a useful PowerShell command to display the backup status of your mailbox databases. Just open the Exchange Management Shell and run the following command:

Get-MailboxDatabase -Status | fl Identity, LastFullBackup, LastIncrementalBackup, LastDifferentialBackup, BackupInProgress

This will generate a report such as the following:

Identity               : System-EXCHSRV1
LastFullBackup         : 5/17/2012 7:00:50 PM
LastIncrementalBackup  :
LastDifferentialBackup :
BackupInProgress       : False

Identity               : MDB03
LastFullBackup         : 5/16/2012 2:59:56 PM
LastIncrementalBackup  :
LastDifferentialBackup : 5/18/2012 10:30:49 AM
BackupInProgress       : False

Identity               : MDB04
LastFullBackup         : 5/17/2012 6:35:16 AM
LastIncrementalBackup  :
LastDifferentialBackup : 5/18/2012 11:31:04 AM
BackupInProgress       : False

Identity               : System-EXCHSRV2
LastFullBackup         : 5/17/2012 7:03:13 PM
LastIncrementalBackup  :
LastDifferentialBackup :
BackupInProgress       : False

Identity               : MDB01
LastFullBackup         : 5/17/2012 6:35:22 AM
LastIncrementalBackup  :
LastDifferentialBackup : 5/18/2012 12:36:38 PM
BackupInProgress       : False

Identity               : MDB02
LastFullBackup         : 5/17/2012 6:35:07 AM
LastIncrementalBackup  :
LastDifferentialBackup : 5/18/2012 1:31:08 PM
BackupInProgress       : False