Validate that IPN call is from PayPal?

Question

How can I validate that a PayPal IPN POST request to my specified notifyURL is indeed coming from PayPal?

I don\'t mean comparing the data to what I sent earlier, bu

Answer 1

If I remember correctly, the PayPal uses a static IP for it's IPN calls.

So, checking for the correct IP should work.

alternatively, you could make use of gethostbyaddr or gethostbyname.