Validate response emails from a list?

I'm shopping around for the right solution for a community group, and they asked if it's possible to validate the email address a user provides against a defined list (say, in Google Sheets) before letting them continue to register.

Hello Christian - If you mean only specified users can submit the form, you can just assign the forms to them. 

Here's a guide for that: https://www.jotform.com/features/assign-forms/.

Now, when you assign a form to an email (of the user), only the users in the list can view and submit the form.

Please try that and let us know how it goes.