When you sign up a cloud account, we suggest you using a valid email address. So if you forget your password, please contact us and we will reset your password and send new password to your email address.
If you use an invalid email address when sign up your cloud account, that's little trouble. If you have made some payments for your account, please update us with your paypal payment information. We will check our database according to paypal information, then reset your password and send the new cloud account information to your email address which is included in PayPal payment.
Finally, if you use an invalid email address as your cloud account, and you never make any payment for your account, then we suggest you sign up a new account with a valid email address and forget your previous account.