Why does Mail.app automatically add iCal events from invitations I receive?
There are web app preferences to manage this in newer macOS.
In the Mail.app go to Preferences-&gt;general. There is an option &quot;Add invitations to ICal&quot; which is Automatic or None. You need to choose None.

When you have a mail with date and time in Mail.App will highlight that and clicking on that will add an event to iCal.