How did you become a moderator of a tech forum? Why do I have explain everything to you five times? Is English your first language? You have a real knack for misunderstanding what people are saying.

Go to System Preferences>Internet Accounts.
At the top of the page, it says "Internet Accounts sets up your accounts to use with Mail, Contacts, Calendar, Messages, and other apps."

You have choices like Google, Yahoo. Now if Proton Mail were one of them, I would not have any problems. I would not have asked this question. I could simply click on the choice. This System Pref proves that it is possible to link Mail or Calendar to internet accounts. One need only uncover a way.

If I have an appointment on Monday at 8 am, I would like Calendar to send me a reminder of that appointment—before it happens. That means sending me an email. ProtonMail is a free internet mail service. I have a Proton Mail account. I would like Calendar to sent me email reminders of my appointments.

Capisce?

Last edited by deniro; 08/22/19 12:48 PM.