Telus Storage Group has two mailbox databases: telus database and Shaw database

Because the Shaw Database has status MOUNTED, restore process will fail.

Dismount the Shaw database:

The restore process will succeed. However, when you try to mount the database, it is possible you get the error message: "
MapiExceptionCallFailed: Unable to mount database". Why?
Two things:
The temporary location D:\temp is not empty.
And the Last Restore Set is not checked.

Because the backup is the last one, I make sure the D:\temp is empty and select "Last Restore Set". After the restore process completes, I could mount the database.