How to send automatic Emails via IPN

I have a bunch of custom codes that I need to send to my buyer as soon as they pay for it. The codes are in a list. Is there any way to do this? Any special programs or something that I can set up?

try to give more info
whats IPN?
how do you have the codes now?
example of the code you have, typing to see if its just a small text or somthing else.

how are they buying? do you have an autoreponder linked to your payment gateway?