On Coinbase under Merchant Profile I'm entering the URL: https://www.scirra.com/handlers/coinbasecallback.ashx

For the IPN tester. This ashx page has the code:

var r = "";
foreach(string name in context.Request.Form)
{
    r +=(name + " = " + context.Request.Form[name] + "<br><br>");
}
r += "<br><br>" + context.Request.QueryString;
Amazon.Emailer.SendEmail("xxx@domain.com","xxx@domain.com","Callback Dat", r);

The email I receive contains absolutely no data, although the logs page on Coinbase implies it's posting JSON data and returning HTTP 200 (success).

Am I doing something wrong? Or is this a broken feature? Can I (semi) safely assume that it posts the JSON in live mode? And if so, do I simply Request.Form[0] to retrieve it or does it have a string index?

Thanks for any help!