How to View the Complete Email Message Source in Outlook

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by Heinz Tschabitscher
Updated June 12, 2018

A "normal" email client stores messages as it receives them—with all the header lines and the body, separated by a blank line. With its Exchange background and a complicated local storage system, Outlook does this a bit differently.

Outlook Takes Internet Emails Apart

Outlook takes messages it receives from the internet apart as soon as it sees them. It stores the headers independently from the message body and breaks out the individual message parts, too. When it needs a message, Outlook collects the pieces to show just what is needed. You can have it display all the headers, for example.

Unfortunately, the original message structure is lost, though. Even when you save the message to disk as an .msg file, Outlook only saves a slightly modified version (the Received: header lines are stripped, for example).

Fortunately, you can tell Outlook to preserve the complete source of internet messages, though. How Outlook operates will not change, but you can retrieve the original source of messages as they were received at any time.

PST Size Will Increase!

Outlook will store the message's source in addition to storing the message's content. This means future emails will take up roughly double the space. Since PST files (where Outlook stores mail) do have a size limit, make sure you do judiciously archive email in Outlook (or delete outright). By the way, you typically can recover deleted emails. 

Make Available the Complete Message Source in Outlook

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

  1. Press Windows-R
  2. Type "regedit"
  3. Hit Enter
  4. For Outlook 2016:
    1. Go to HKEY_CURRENT_USER\­­Software\­­Microsoft\­­Office\­­16.0\­­Outlook\­­Options\­­Mail.
  5. For Outlook 2013:
    1. Go to HKEY_CURRENT_USER\­­Software\­­Microsoft\­­Office\­­15.0\­­Outlook\­­Options\­­Mail
  6. For Outlook 2010:
    1. Go to HKEY_CURRENT_USER\­­Software\­­Microsoft\­­Office\­­14.0\­­Outlook\­­Options\­­Mail
  7. For Outlook 2007:
    1. Go to HKEY_CURRENT_USER\­­Software\­­Microsoft\­­Office\­­12.0\­­Outlook\­­Options\­­Mail
  8. For Outlook 2003
    1. Go to HKEY_CURRENT_USER\­­Software\­­Microsoft\­­Office\­­11.0\­­Outlook\­­Options\­­Mail
  9. Select Edit | New | DWord from the menu.
    1. Select DWORD (32-bit) Value with 32-bit Office
    2. Use DWORD (64-bit) Value with 64-bit Office (which is unlikely)
  10. Type "SaveAllMIMENotJustHeaders"
  11. Hit Enter
  12. Double-click the newly created SaveAllMIMENotJustHeaders value.
  13. Type "1"
  14. Click OK
  15. Close the registry editor
  16. 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):

  1. Open the desired message in its own window.
    1. Double-click the email.
  2. Click FILE.
  3. Make sure the Info category is open.
  4. Now click Properties.
  5. Find the source to the email under Internet headers:.
  6. Click Close.

See the Complete Source of a Message in Outlook 2003/7

To open a message's full source in Outlook 2003 and Outlook 2007:

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

(Updated July 2016, tested with Outlook 2003, 2007, 2010, 2013 and 2016)