No fecking clue
I went to the website - which is working fine. Decided to sign-up for the "Backstage" service. I'm at work but used my home email address. TWO HOURS later the confirmation email turns up on my Windows Mobile phone (nothing to do with my Exchange server or the connection. It just took them that long to send it out).
"Thanks for registering. To confirm your registration just click here or paste the URL below into your browser"
Tapped here. Opens up in Pocket Internet Explorer.
"We're sorry. We don't currently support your browser. Please complete the registration process from your desktop".
So, the sign-up process for Windows Mobile doesn't support Windows Mobile.