As Josh says, use a form rather than FTF. JD's solution is clever, but if I understand it, it is designed for someone forwarding the post-registration email but not the original invite. You would want a solution for both use cases. The short description of how-to: You would create extra fields for the data about the friend, like first name and email. Use a webhook to add the person to the database and then do the appropriate emailing. You can add the name of the person from whom it was forwarded by in the email to the friend. This is a general solution to any referral program, where one person is recommending another for an activity.
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