A working email address is required for PXO registration.
Without it, you will be unable to complete your registration. Your email address will not be given to solicitors, bulk emailers, or anyone else.
PXO is not a standalone gaming service. It is designed to work with Volition/Outrage games like Descent: FreeSpace, Descent 3, and FreeSpace 2. If you created a PXO account for one of these games, you do not need to register again to play another.