Outlook must be running for you to get the calendar reminders.

You can setup Outlook so that when you minimize the application, it will only show up in the system tray. When Outlook is open,right-click on the icon in the system tray, on the menu you seen “Hide when minimized”. Check it if it is not already checked. That’s it; now instead of closing the application minimize it and it will start running in the background and you will be able to receive all the notifications. Next time when you need to use Microsoft Outlook double-click the icon in the system tray.