How do I allow only one submission per email address?

Creating a form on which we will upload email addresses through the spreadsheet to form widget and allow them to continue only if they input an email address included in spreadsheet.

Is it possible to only allow one order per email address on the published form?  Want to both restrict to uploaded email addresses but also restrict an email address to only one order.

You can set 'Unique Submission' or 'Unique Question' for protecting your form.
Please look at this for setting one submission per one email address:

You can set unique questions based on your form fields. More information is here:
https://www.jotform.com/help/223-How-to-set-Form-Limits-Based-on-a-Unique-Question

Let us know if you have further questions.

Thanks.