The Can Spam Act
In response to public pressure, Congress enacted this law and made
it effective January 1, 2004.  The law requires that a solicitation Email contain one of two things-- a functioning “opt out” link
or a legitimate “reply to unsubscribe” E-mail address.  Many unethical spammers continue to ignore this law and trick unknowing recipients into responding to a fake “opt out” link.  In reality, all the responder is doing is verifying to the sender that his E-mail address is a valid one.  You may want to reconsider before “replying” to such.