I'd suggest looking into PayPal Instant Payment Notifications (IPN).
PayPal IPN allows you to process order information while not having to depend on the buyer to return to your website.
You can use IPN by setting up a script which receives the data on your website, and subsequently send an automatic 'Thank you' email to your buyer.
To start using PayPal IPN, include the following extra code along with your button(s): For Website Payments Standard (where "xxxxxxxx" is the full URL to your IPN script):<input type="hidden" name="notify_url" value="xxxxxxxx">
Or alternatively, navigate to 'Profile' > 'Website payment preferences' and enter a value for the 'IPN URL'.
Additionally, you can find sample code, documentation and further information on PayPal IPN at https://www.paypal.com/ipn
If you're not a developer, or if you'd rather have someone develop this for you, you can find certified third-party developers at https://www.paypal-portal.com/developer/directory/
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