This article applies to Microsoft Outlook 2010 and 2013

Step 1:

Open Outlook

Outlook 2010 Inbox

Step 2:

Open the email you want to view the header for, click "File"

Outlook 2010 Email

Step 3:

Click "Properties"

Outlook 2010 File

Step 4:

The section"Internet Headers" is the email header

Outlook 2010 Header