An automated e-mail system on the Internet, which is maintained by subject matter. There are thousands of such lists that reach millions of individuals and businesses. New users generally subscribe by sending an e-mail with the word "subscribe" in it and subsequently receive all new postings made to the list automatically. Mailing lists are also called "listprocs" and "listservs," the latter coming from the popular LISTSERV package. Majordomo is a popular public domain mailing list program.