Are “challenge-response” spam blockers a good solution to the spam problem?
In our opinion, no. First, they are bound to annoy your correspondents. If you use one, when someone sends an e-mail to you, the message is bounced back to the sender, who then receives an e-mail instructing him to visit a web site that challenges him with a CAPTCHA (an acronym for “Completely Automated Public Turing test to tell Computers and Humans Apart”), in which a user must visually decipher and then type the distorted (or otherwise obscured) sequence of letters or numbers that appears on the screen, such as in this example: If the sender correctly deciphers the CAPTCHA, his message is then forwarded to you. At best, this delays your receipt of his message and makes sending a message a multi-step process that could stretch out over a period of days. At worst, you may never see his message because he did not respond to the challenge request (which could easily be overlooked in an inbox cluttered with spam and countless other messages). Or he may have tried to respond, but he could
