> Why is it my responsibility as a holder of a valid email address to accept > mail from anyone who wants to send me the mail? As the owner of the email > address or, as the admin of the domain's mail server, I have no obligation to > accept your mail at all. > Obligations should be on the sender.
I will respectfully disagree. I believe you are pushing the burden onto the sender rather than have your system accept the reponsibility of reviewing messages for you. The C/R basically works the same way except the challenge goes to the recipient. Just a different concept. Personally, I won't employ either one. And if the sender acknowledges the C/R, if the sender is not a "bot" but is still from a source you don't want sending you email - what control do you have over that?
