Mailing lists are among the electronic communications services that are older than the WWW (World Wide Web). In the beginning, a simple program duplicated all messages received and forwarded them to all subscribers of the list. Today this can be done by a program on a server.
For many people mailing lists are an ideal supplement to interviews and magazines, because mailing lists are worldwide and always available. Since the timetable allows less and less real meetings, many topics can be spread and discussed via mailing lists and thus prepare real meetings optimally.
A program like Mailman has many possibilities for user administration, archiving, filtering, etc.