To set up Outlook so you can see the complete source of emails:

• Press Windows-R
• Type "regedit".
• Hit Enter.
• Go to HKEY_CURRENT_USER\­­Software\­­Microsoft\­­Office\­­12.0\­­Outlook\­­Options\­­Mail.
  • For Outlook 2003, go to HKEY_CURRENT_USER\­­Software\­­Microsoft\­­Office\­­11.0\­­Outlook\­­Options\­­Mail.
• Select Edit | New | DWord from the menu.
• Type "SaveAllMIMENotJustHeaders".
• Hit Enter.
• Double-click the newly created SaveAllMIMENotJustHeaders value.
• Type "1".
• Click OK.
• Close the registry editor.
• Restart Outlook if it has been running.

See the Complete Source of a Message in Outlook

Now you can retrieve the source of newly retrieved POP messages (editing the SaveAllMIMENotJustHeaders value does not restore the complete message source for emails that were already in Outlook):

• Click on the desired message with the right mouse button in the Outlook mailbox.
• Select Options... from the menu.
• Find the message source under the (now improperly named) Internet headers: section.