|Message ||Outlook gives you the option to View --> Options which will display the e-mail header (similar to Outlook Express). To enable the View --> Source functionality in Outlook 2003 open up regedit and drill down to:
Create a new Reg_DWORD called SaveAllMIMENotJustHeaders and give it a value of 1.
This will enable the View --> Source option in Outlook 2003 but there are a few exceptions. It will only work for messages received after the change has been made and will not work with MAPI connections (like Exchange mailboxes). You will only have this option for mail received from Internet transports (like POP3, imap, ect...)