Most likely cause Operamail, on default, is a free mail service. Only if you upgrade it, it's paid. Makes you wonder why someone pays for 25 MB mail storage when you can have a "bit" more for free on Google, etc...
aye, if there is some way of confrming a subscription to such paid/free email sites we can allow them on a case-by-case basis.
It'd probably be quicker if you used your ISP email though. We only use your registration email once, to send you your initial password, after that you can change it to any email you like.