Bedankt meneer!
I think that you are referring to "reminders"
Here's what I found:
"You can send a meeting request and not track the attendees' responses. Not tracking the responses can be useful when you send a meeting request to a large number of attendees and tracking attendance is not necessary.
- On the File menu, point to New, and then click Meeting Request.
- On the Actions menu, click Request Responses.
This turns off the Request Responses option. To turn back on requesting responses, on the Actions menu, click Request Responses."
Groetjes!