HI All,
As per my experience with BE12.5, not able to restore a single mailbox if mailbox has been removed or disconnected.
If you check GRT opetion after that also it will not work, this is a major issue with BE12.5.
I tried lot of triks and steps to restore the mailbox but always it give errors or failed status.
You can take backup of Exchange MailBox without any problem if you had right configuration, but it will not work for a single mailbox if mailbox was deleted or active directory object was deleted due to any reason.