How to retrieve email addresses in my Outlook 2007.

I have a problem with my Microsoft Outlook 2007. It displays the sender’s name instead of the e-mail address. I cannot retrieve the address by double clicking the name or by clicking the “show header”. When I reply to such mails, Outlook tells me that it can’t recognize the name (not found on my address book). When I use Windows Mail, I did not encounter this problem. Anyone can explain me why is this happened? Thanks!
