You need to add mail-tags to the fields in the Mail tab panel. These tags need to correspond to form-tags used in the Form tab panel. For example, when you used a form-tag [text your-new-field], the corresponding mail-tag that you should use in the Mail tab is [your-new-field]. For more details, see How tags work.
A mail-tag in the Mail tab panel will be replaced with the user input to the corresponding form field.