The idea of these programs is very simple. The program has an email address, usually with the term listserv or majordomo in the name. (Listserv and Majordomo are the two main types of programs used to do mailing lists). A person who wants to join the list could send a command to the majordomo program through his email client asking to sign on. All members of the list is given another email address for the actual list, which is also controlled by the majordomo program. When a member sent a message to the list, the controlling program would automatically send it to each member of the list.