Getting attendees to enter their email address as they enter a zoom (ie those that attended)

I attended a Zoom meeting recently and they asked me to type my email in as I was entering the Zoom.

How do we get people to do this as they enter our Zoom? And then access these emails after the zoom.

I want the emails of those that actually attended. I already have their email to be notified of my zoom, I just want to send a specific email to those that actually attended.