When selling products on a Jamstack site, Netlify Functions can be used to automate order fulfillment by sending an email to the fulfillment provider when a payment has been made. This tutorial uses Sendgrid to send transactional emails and demonstrates how to set up the project with environment variables, install dependencies, create a serverless function to receive the webhook event and send the email, verify the webhook signature, forward webhook events to a local server using the Stripe CLI, deploy to production by adding a new webhook endpoint in the Stripe Dashboard.