How do I send an automatic receipt and thanks for a donation/payment?

[Buzz88]

See the title.

[sharpiemarker]

PayPal already sends out a confirmation email to the sender. But check out this integration guide for how to add a thank you message:

https://developer.paypal.com/docs/classic/paypal-payments-standard/integration-guide/checkout_exp_do...

See this at the bottom:

Payment Data Transfer — Return transaction information to donors after completing a donation, including a Thank You message.