Set up taxonomies to populate as checkboxes, but not showing up in email message

Hi All,
I have a form on my site that a visitor can use to register their company to be placed in my directory. I have set up text fields in the form that are then populated/replaced with check boxes for each of the custom taxonomies that are used for categorization. Everything shows up fine on the form in the front end. I'm using the gform_pre_render_ID method to filter the form's inputs.

But when I receive the email with information all of the dynamically populated check boxes are not shown, as if the visitor did not check any of them. What could be causing this? DO I have to place all of these taxonomies in the form as checkboxes to get this to function correctly?

Thanks for your help!