Outlook 2010
  1. Open the Message in Outlook
  2. Click the File tab
  3. Select the Properties button
  4. Right-click in the Internet Headers box and choose Select All
  5. Right-click again in the Internet Headers box and choose Copy
  6. Paste that data into a reply to an email
Outlook 2003/2007
  1. Right-click the message and select Options
  2. Right-click in the Internet Headers box and choose Select All
  3. Right-click again in the Internet Headers box and choose Copy
  4. Paste that data into a reply to an email