Show all folders

To see the Folder List, on the Go menu, click Folder List.
To expand folders and see subfolders, click . To collapse folders and hide subfolders, click .

Notes

Favorite Folders is available only in the Mail pane. The Favorite Folders pane cannot be removed, hidden, or resized. Only mail folders can be added to or removed from Favorite Folders. It is not possible to display Favorite Folders in other panes, such as Folder List.
The Folder List pane cannot be moved, but can be resized.
If you prefer to see all your folders, and not just your mail folders, change the Folder List button into a large button and then either move it above the Mail button or remove the Mail button from the Navigation Pane.