If you want to troubleshoot the validity of a message or an antispam assessment in Microsoft Office Outlook 2003 or later, you can change the registry to provide more information about a message than just the headers.
Inbound messages from the Internet to Microsoft Office Outlook with POP have associated Internet headers outlining the source and routing information about that message. To troubleshoot the validity of a message or server-side antispam assessment, start by checking the message headers. The headers shown in Outlook don’t include the message content by default. Starting with Outlook 2003, a registry change can be applied to provide more complete information about an email message.>
In the Registry Key:
Add the DWORD “SaveAllMIMENotJustHeaders” and assign a value of 1.
The \[version\] is 11.0 for 2003 and 12.0 for 2007.
Outlook reads this key on start up, so to effect the change Outlook will need to be restarted. Now the entire message source is available in a single place. In Outlook 2007, you’ll find header content by expanding the Options ribbon object on a message. This opens the Message Options dialog box shown in Figure 1. For remote clients using POP3, the administrator can request the entire message source to assist in troubleshooting measures. The user can highlight the content in the Internet headers box in Message Options and send it in.
This setting puts the entire message source in the same place where previously only the message headers were shown. If you make this change, messages stored in .pst files will take up more room. The header content now contains another representation of the message which needs to be stored. It applies only to new inbound messages and does not add message source to existing messages already downloaded from the server.