Limit duplicated registrations

[ES0729]

Is there a function to detect duplicated registrations, such as by email addresses, and stop them from re-registering? 

We are hosting a webinar with a maximum capacity of 100 people. In the past, there were unintended multiple registrations from the same person, so some seats were taken and we couldn't serve 100 people. 

[AshC]

@ES0729  If you attempt to register using the same email address, the webinar system should note it already exists, and not duplicate the registration info.  Have you already tried reviewing registrant info before confirming them for the live broadcast?