Minimize Outlook to System Tray in Windows
1] Minimize Outlook to System Tray using UI
If you wish to open Outlook again, simply double-click on the Outlook system tray icon, and it will open.
2] Using Registry
If you wish to make the change by editing the Windows Registry. After you have created a system restore point, Run regedit to open the Registry Editor, and navigate to the following key:
In the right pane, give MinToTray DWord, a value as follows:
0 : Will minimize Outlook to the Taskbar1 : Will minimize Outlook to the System Tray
A small but useful tip!
Outlook closes when minimized
If you think that Outlook closes when you click on the minimize button, then know that it does not close but is actually minimized to the Notification area. To change this behavior and make the Outlook windows minimize to the taskbar, uncheck the Hide When Minimized option as explained above. Check this post if you want to find out how to add Holidays to Outlook Calendar.