Unfortunately what you would like to do is not directly supported - that would be too easy. PayPal does have a function called IPN or Instant Payment Notification which with some custom scripting could send automated emails to your customers from your server. You can find more details here. Some businesses simply send a email from their email client as separate action to their customers. And if you're selling from your website, you can create a custom Thank You page that the customer is redirected to after completing the payment process.