What is Challenge/Response?
Challenge/Response is a system that requires the sender of an email that he/she actually sent the email, in most cases the majority will be spam. Re-confirmation must be provided manually for Challenge/Response to work. If the e-mail was sent by a mass-mailing system, there is usually no human at the email address that is used in the “From” header, thus re-confirmation cannot be provided. Pending senders are authorized or denied by the Challenge Response system automatically, however, it will also be necessary to manually maintain this from time-to-time. The most convenient way to manually maintain the Challenge/Response pending e-mails is via the Web Mail which contains the special section under “Settings” called “Challenge Response”.
