The answer is : At this time you cannot see the email header from Windows 10 mail App.
The solution. Open the email using Internet browser, (also you can use email client software, like Microsoft Outlook, Mozilla Thunderbird, etc, but you have to setting account first, take a time).
• Open Microsoft email (live mail, hotmail, outlook.com) using internet browser.
• Right-click on the email that you want to see it's header.
• Choose View message source.
You will see the email with it's header.
