See it all

. . . you can view the header and source together in the options dialog, if you edit a registry key. This works on mail downloaded from Internet mail transports only, not Exchange server mailboxes. However, if you access the mailbox using an Internet transport, you'll see the full source.
Open the registry editor and navigate to:

HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Options\Mail

Right click on the right pane and choose new DWORD:

Parameter: SaveAllMIMENotJustHeaders
Value: 1

Labels: General, Tips, Tutorials