How to add email Reminder Action to Lightning event?

In Thunderbird Lightning, when creating or editing a calendar event, how do we add an email alert? My Lightning offers only Display alert / Afficher une alerte. I need a Reminder Action able to Send an Email Message.

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Below is the same question as above. But with details if you’re interested in those.

By “email alert” I mean, for example, 1 hour before an event, an email message reminder is automatically sent to a set email address.

What I tried that did not work:

  • Clicked on the Choose a Reminder Action/Choisir une action de rappel drop down menu. Only one option is available. It reads Display alert / Afficher une alerte.
  • Double-checked that the calendar is a Network Calendar (CalDAV)
  • Double-checked that the calendar Properties as an email address associated to it
  • Searched for add-on about email alert at I found none able to do email alert.

Synonyms of calendar email alert:

  • alarm mailing
  • reminder action
  • send email reminder
  • thunderbird notification by email message