If you’re finding emails from your Windows Mail or Outlook Express inbox go missing right after you’ve read them, closed the program, then reopened it, don’t panic. Most likely, the messages are perfectly safe, and you just managed to accidentally change a setting in Windows Mail that hides messages once you’ve read them.
It’s easy enough to fix. From the menu, select View > Current View; you will see that Hide Read Messages is checked. Click Show All Messages and the problem is solved.