Can I add custom fields to my form?

SendFox only captures email address, first name and last name. At the moment, it is not possible to add custom fields to a SendFox form. 

You can use Sumo to create forms with custom fields. Sumo provides a free account option and integrates directly with SendFox. Unfortunately, you will not be able to pull this extra information into SendFox but you can download it from Sumo.