These steps will show you how to view the internet headers in Outlook 2013.  This will also work for Outlook 2010 but has not been tested on any other versions.

Step 1

Double Click on the Email Message << This bit is important.  If you only highlight the email message you won’t see the correct options after clicking on file.

Step 2

Click on File from the top left menu.

Step 3

Click on Properties.  You should now be able to see the internet headers in the box at the bottom

Internet Headers Outlook 2013