When I was a PC user, I used Outlook very often (not to be confused with Outlook Express). Over the years it has become a much better application. I pretty much stopped using PCs around 2003. I have to admit I did like Outlook at the very end.
1. Open Outlook.
2. Open an email message in a new window (double click).
3. Select View -> Options from the menu.
4. A dialog box will pop open.
5. The headers can be found at the bottom of the dialog box, in the section called Internet Headers.