Currently, an indispensable function of any email client worth its salt is that it can be minimized and hidden in the background, to appear only in the event that a new email message is received. Outlook Express does not include this option by default, but you can add it by installing this small program: OETray.
OETray minimizes the Outlook Express client to the system tray, and allows you to work with it in the background. The program does not require any installation, and does not consume system resources. Small, effective and completely free.
You can free download OETray 32, 64 bit and safe install the latest trial or new full version for Windows 10 from the official site.