FYI – I have exactly the same issue as Miles – when I attempted to request the key from the email address linked with my PayPal, I got this back from your mail server:
<register@vorpx.com>: host vorpx.com[212.227.15.41] said: 550
invalid DNS MX or A/AAAA resource record
I’ve already created a separate post though to send it to my gmail address (which I’ve sent to your registrations email address) along with my original purchase email address for verification.