In addition to the pre-defined system folders such as Inbox, Sent, and Trash, you can create custom folders. Custom folders can be created inside other folders, including the system folders.
You cannot create two folders with the same name within the same parent folder. For example, you cannot have two folders named "Shopping" under your Inbox folder, but you could have one folder named "Shopping" under your Inbox folder, and another one with the same name under the Sent folder.
Right-click in the Overview pane in the Folders list and select New Folder. A Create New Folder dialog opens.
Type a folder name.
Select where to place the new folder. Click Folders to have the folder at the top level or choose a location from the list of existing folders. Your new folder is placed within the selected folder.
Click OK.
To create a folder tied to an RSS or ATOM feed, check Subscribe to RSS/ATOM feed, then enter a URL.