Electronic mail blocking system

An electronic mail blocking system for reducing undesirable electronic mail that a recipient receives. The electronic mail blocking system filters one or more electronic messages transmitted by a sender having a sender identity to a mail server addressed to a receiver. The electronic mail blocking system comprises comparing the sender identity to an authorized sender list and transmitting the electronic message if the sender identity matches a record within the authorized sender list. The mail server automatically transmits an authentication request containing a question to the sender when the sender identity does not match a record within the authorized sender list. A response containing an answer from the sender in response to the authentication request is compared to a correct answer. If the answer is a correct response to the question, the mail server transmits the electronic message to the recipient and automatically adds the sender to the authorized sender list.