A client is collecting data on how many people are at their end client's company. They would like to do this via email. However, it is not possible to add a text field in the email invite itself as this is only possible at the moment in email with AMP, which isn't widely supported. So it can't be done in Vuture, or across most email inbox providers.
For interaction with a contact, we would recommend using forms or surveys, that act more as webpages, allowing for more interactive elements.