[Forminator Pro] Provide Double-Optin to Forminator Pro

I have setup a simple order-form at https://hilfe.macbay.de/mpress-bestellung/ where the submitting client will receive the order-confirmation email after sending the form.

With regard to the upcoming GDPR I need an additional process, where the client will confirm the order or at least his email-address by clicking a confirmation link to be send to the client prior to sending him the order-confirmation.
How can I achieve this?
Thank you and kind regards,