How to add "Add to Calendar" links to your built in reminders

You can go to any of your email reminders, click on Customize, and then scroll down to find this option

How to Customize email reminders is shown > HERE

Calendar links from the email reminders are not setup by default, you can turn those On if you like,

a select switch when configuring any of the email reminders individually, can be found at bottom of each reminder (as shown below)

Click on it and then hit save. That's it!