title: Checking a guest customer's email address before order is processed to prevent them from purchasing multiple sample products
body: <p>Hopefully there's a woocommerce veteran familiar with the checkout process that can help me with this. My store offers a sample product at a discounted price, but I want to limit this to a one-time order per customer. I've found a <a href="https://www.skyverge.com/blog/prevent-repeat-purchase-with-woocommerce/" rel="nofollow noreferrer">solution that works for registered users</a> but I was wondering if there's another way to make this work without forcing guests to set up an account before ordering the product.</p>
  
  <p>What I was thinking was if there's a way to check if the customer's billing email address has ordered this particular product at the checkout stage. So they'd fill out the checkout form and click "Proceed" but before the customer is taken through to the payment gateway their email address would be checked for ordering this particular product before, if so, direct them to a "order failed" page rather than through to the payment gateway.</p>
  
  <p>Thanks in advance!</p>