The PayPal Sandbox IPN worked perfectly on Friday, May 31, 2013. Since Saturday, June 1, 2013, it refuses IPN verification calls with an HTTP response code of 0 (using cURL for the IPN verification call), and an empty (0 characters) response body.
When one leaves everything in the IPN verification call the same, but just change the URL from https://www.sandbox.paypal.com/cgi-bin/webscr to https://www.paypal.com/cgi-bin/webscr you get an HTTP code 200 and a response body containing "INVALID", which is expected, but demonstrates that there is a problem with the Sandbox IPN.
We've tried the verification calls from different servers and it did not make a difference.
It appears as if something changed during the night of May 31 that broke the Sandbox IPN.
It might be related to the fact that the x.com domain is not responding at all. www.x.com also worked fine on Friday.
Is anyone else currently able to successfully send an IPN verification to the Sandbox IPN?
