What gems/plugins that make it easy to add a tamper-resistant unsubscribe link to the bottom of the email a user can click to prevent receiving email those types of emails? The only thing I could find was http://kevinlochner.com/handling-unsubscribe-requests-in-ruby-on-rail which works but is somewhat unsophisticated and lacks features such as which type of emails to unsubscribe from. It also doesnt include the mechanism for users to unsubscribe. We using ActionMailer.