Hello,
Check your settings, there should be an option to turn off read receipts. Read receipts are generally not reliable, many email services do not support them.
Also, I recommend that you upgrade from Windows XP. You're not getting security updates anymore. Everything you do from the files on your computer to activity on the internet is at risk.
As of this posting I recommend updating to Windows 8.1 and using the new mail program called
Windows Live Mail.