When was HTTP 1.0 support discontinued on www.paypal.com?
Where can I find IPN, PDT sample scripts that comply with HTTP 1.1 specification?
You'll find samples at GitHub and StackOverflow. If you're unfamiliar with this process or use a third-party shopping cart, contact the individual support channels for your cart to help facilitate any change that may be needed.
Why does HTTP 1.1 require the "Host" header?
Refer to this Internet address conservation whitepaper for further details.
What if I don't make these changes to my IPN/PDT scripts?
PayPal returns HTTP 400 to any requests to www.paypal.com without the "Host" header in the HTTP request.
Where I can test my IPN/PDT scripts?
Run your tests in the PayPal Sandbox. The Sandbox is configured to return HTTP 400 to any HTTP requests without the "Host" header.
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