Gmail has done this since 2009, though it depends on good behavior from the sender. http://gmailblog.blogspot.com/2009/07/unsubscribing-made-easy.html http://g

Gmail has done this since 2009, though it depends on good behavior from the sender. http://gmailblog.blogspot.com/2009/07/unsubscribing-made-easy.html http://gmailblog.blogspot.com/2009/07/unsubscribing-made-eas...