This new option is now available for Office 365 Home, Personal, Business and ProPlus subscription customers as well as for other subscription customers. This option will be available after upgrading to version 1808.
To turn this on from Outlook:
- Click “File”
- Click “Options”
- Click “Advanced”
- Look for the “Reminders” section
- Check the box next to “Show reminders on top of other windows”.