You want to offer a digital file for sale and send it to customers via email after payment is received, using a combination of payment providers, file hosts, and email services. Zapier can help you automate this process by connecting different tools and creating custom email templates with links or attachments. You have three main options: Direct Link Method, Attachment Method, and Expiring Link Method, each with varying levels of complexity and customization possibilities. The most powerful method, Expiring Link Method, uses Amazon S3's custom URL signing app to generate expiring download URLs, but requires more setup and configuration.