Hi partner,
Sending invitations automatically for appointment is by design in D365, and if you want to stop it, you need to stop it in exchange cause it will sending emails by exchange. I created an appointment in my instance and I monitored the system jobs, I found that there was no jobs triggered after created the appointment, so it's exchange that send the emails.
No such job that send invitations.
You should create a plug-in in D365 when creating and updating the appointment to add special tag in the body to let the exchange know it is an appointment invitation send from D365 and then create exchange rule to prevent sending these emails which contains the special body.
You could refer to this blog for more details.
https://dynamics.mittermair.pro/2019/01/06/stop-sending-appointment-invitation-to-attendees/
In the first step, to add special text in body, you could also use FLOW to do this.
Best Regards,
Leo
