I agree 100%. We desperately need this functionality to limit form submissions to a unique email so we don’t risk over-writing prospect and webinar event attendee contact records.
I love the suggestion to allow setting up a pop-up message that says, this email was already submitted on this form. Please enter a unique email. (It would be great if this message was configurable.)
We run into this issue often with one person registering multiple people to attend an event or training from the same company. Thanks in advance!