Dear Sender:
There's nothing more annoying than clicking that 'unsubscribe' link at the bottom of your email only to be asked to login first. I know it sucks when people opt-out of your transactional emails, but deal with it and let people unsubscribe with one click. If you do this you may even get some valuable feedback.
If your transactional email provider doesn't have a single-click unsubscribe option, find another service. I recommend every developer test out what a recipient sees.
Sincerely,
Users of the Internet
It's shitty UX regardless of whether it's a violation of law, IMO.
Original: It's a violation of CAN-SPAM law to put unsubscribe behind a login process. Asking for a password violates the requirement that no additional PII except for the email be required to process the opt-out.
From the FTC:
Honor opt-out requests promptly. Any opt-out mechanism you offer must be able to process opt-out requests for at least 30 days after you send your message. You must honor a recipient’s opt-out request within 10 business days. 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.
http://www.business.ftc.gov/documents/bus61-can-spam-act-com...