Updated: May 2
Article No :: KB00005
Minimize Outlook to System Tray
Like most applications Microsoft Outlook will normally minimize to the taskbar. This setting changes the default behavior so that it will minimize to the system tray (next to the clock) instead.
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Open your registry and find the appropriate key below.
Create a new DWORD value, or modify the existing value, called "MinToTray" and set the value "1" as shown below.
Exit your registry; you may need to restart or log out of Windows for the change to take effect.
For example: Registry Settings for “Microsoft Outlook 2016 / Office365”
User Key : [HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences] Value Name : MinToTray Data Type : REG_DWORD (DWORD Value) Value Data : (1 = System Tray, 0 = Taskbar)