After setting up an aspx page that accepts IPN postings from PayPal on my domain, I got this error when trying to post IPN data:
The remote server returned an error: (999) No Hacking
Well, I didn’t have this problem with my previous hosting company, nor when trying on my local IIS web site. So I contacted Webhost4Life, on their live chat support. That didn’t help much. But I finally found the solution.
It turns out that Webhost4Life has a functionality called Security Guard. Turning this off for my sub domain did the trick.
You will find the Security Guard in your Control Panel, Security section.