http://www.figby.com/archives/2004/11/04/challenge-response-mail-filters-block-themselves/ A weblog by Michael Moncur Tue, 07 Feb 2012 09:19:35 +0000 hourly 1 http://wordpress.org/?v=3.0.5 http://www.figby.com/archives/2004/11/04/challenge-response-mail-filters-block-themselves/#comment-1447 Anthony E. Greene Mon, 28 Nov 2005 09:13:29 +0000 /?p=3266#comment-1447 <p>The challenge system needs to have some integration with the protectee's mail sending sytem. My own challenge system checks for an In-Reply-To header on incoming messages. If the header exists, my system checks the specified message-id against the message-ids in my Sent messages. Basically if it's a reply to a message that I sent, it gets through.</p>