Mac CalDav: Creating an event with attendees no invitation email sent

Operating System: Linux 5.4.0-77-generic x86_64
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The issue you are facing:

Steps to replicate it:

  1. Connect a Nextcloud calendar to MacOS or iOS calendar
  2. Create an event with an attendee
  3. See no invitation email being sent

When creating an identical event in the same calendar directly on Nextcloud, the invitation is sent as expected. However, even there a simple Accept in the RSVP bar in Outlook/Gmail does not report back to Nextcloud that the event has been accepted.

SMTP is setup as it should be.

Anyone any ideas?

Does no one have any ideas?