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  1. Open Mail.
  2. From the Mail menu, select Preferences.
  3. Click the Viewing icon.
  4. Click the arrow box on the Show header detail pop-up list and choose All.
  5. Close the Viewing window. The e-mail headers should now be displayed in the message.
If you intend to send these headers to another person for review, then double-click the message.
  1. Click the Forward button.
  2. Finally, fill in the To field and send the message.