Do one of the following:
If you want to create a folder to which you can drag items for safekeeping or to distribute to another computer
Create a new data file Personal Folders file (.pst) (Personal Folders file (.pst): Data file that stores your messages and other items on your computer. You can assign a .pst file to be the default delivery location for e-mail messages. You can use a .pst to organize and back up items for safekeeping.) and drag items to it. If you used the default name for the folder when you created the data file, the folder will be called Personal Folders. In the Folder List (Folder List: Displays the folders available in your mailbox. To view subfolders, click the plus sign (+) next to the folder. If the Folder List is not visible, on the Go menu, click Folder List.), drag any item from your current folders to the new folder. Press CTRL while dragging to copy items instead of moving them.
If you want to create a .pst containing Outlook items but still keep the original data in your default folders
Export (copy) items to a Personal Folders file (.pst) (Personal Folders file (.pst): Data file that stores your messages and other items on your computer. You can assign a .pst file to be the default delivery location for e-mail messages. You can use a .pst to organize and back up items for safekeeping.). You can only export one folder at a time, but you can include the subfolders under that folder. For example, you can export your entire [Mailbox - Username] including all subfolders.
If you want to automatically back up or delete items that are over a certain age
Use AutoArchive to move items to an archive Personal Folders file (.pst) (Personal Folders file (.pst): Data file that stores your messages and other items on your computer. You can assign a .pst file to be the default delivery location for e-mail messages. You can use a .pst to organize and back up items for safekeeping.). Unlike exporting, where the original items are copied to the export file but are not removed from the current folder, archiving copies items to the archive file and then removes them from the current folder. AutoArchive allows you to set up a schedule and archive multiple folders at the same time at set intervals.