Bye-Bye Mailchimp

On the topic of unsubscribing from newsletters that use MailChimp, I've had massive issues with being able to unsubscribe. It had actually gotten to the point where I was tired of clicking the button and going through the steps, and instead sent it straight to spam. It has only been some newsletters that use MailChimp. I wonder how MailChimp keeps their subscriber list and how do they let their user know if someone has 'successfully' unsubscribed.