Challenge response systems shift the burden from the recipient to the email publisher. Each email sent by the publisher is first challenged by a challenge response system where it has to be confirmed by the publisher for it then to get through to the recipient. It is felt that spammers would be unable to confirm millions of messages. http://www.squidoo.com/stopspamstopspam Sat, 06 Sep 2008 01:55:35 -0600 FeedCreator 1.7.2 http://spamresearchcenter.blogspot.com Free and Effective Anti SPAM Software Points: 1 Sat, 06 Sep 2008 01:55:35 -0600 http://www.spamresearchcenter.com Free Challenge Response Anti SPAM Software. Points: 1 Sat, 06 Sep 2008 01:55:35 -0600 http://www.spamarrest.com Spam Arrest uses challenge-response technology to block spam from clogging your Inbox. Points: 0 Sat, 06 Sep 2008 01:55:35 -0600