Question

How do I identify empty mail folders in Apple Mail?

Answer

In Apple Mail (v6) mail folders that only contain other folders display as a folder outline in the Mailboxes column, such as "CampusAdmin" and "Faculty" in the attached screenshot. Folders that contain messages and folders display as a grayish shaded folder.

Unfortunately, it is not recursive. When a folder ("CampusAdmin") that contains a subfolder ("Empty") that only contains folders, the subfolder ("Empty") looks the same as a folder with messages.