This may be in violation of US law:
> You can’t charge a fee, require the recipient to give you any personally identifying information beyond an email address, or make the recipient take any step other than sending a reply email or visiting a single page on an Internet website as a condition for honoring an opt-out request.
I wonder if requiring a login means that additional personal information is sent, or that the recipient must perform additional steps other than visiting a single page.
https://www.ftc.gov/business-guidance/resources/can-spam-act...