The CommVault Exchange Mailbox iData agents do not backup mailboxes associated with disabled Windows user accounts. The backup job reports a "success" for the job, but when the details of the backup are explored, the backup set does not contain any data. Additionally, requesting a listing of all failed objects for the backup job results in a "no failures" status. According to CommVault, this behavior is by design as is the "successful" backup status. After all, the job did not technically fail if it is not designed to include mailboxes belonging to disabled user accounts. This is very strange given that, in general, CommVault iData agents have an "inclusive by default" behavior.  This can become a real problem if you try to restore data for a former employee whose Windows user account was disabled when they left the company.  The lesson here is that you should always test your backups. Even if the backup report and all job status notifications indicate you are good....test anyway.