Mailing list
An address that forwards every message to all subscribers — the network's oldest form of group discussion.
On ARPANET, lists appeared almost as soon as email itself. MsgGroup started in 1975 to discuss how email ought to work, and a few years later SF-LOVERS proved that people would rather talk about science fiction. Subscriptions were handled by hand: the convention was to write to the list name plus -request, where a human added or removed your address.
With LISTSERV in 1986 machines took over that job, and out of that came the classic list problems: unsubscribe requests sent to the whole list instead of the robot, autoresponders bouncing off each other in endless loops, and the digest format for anyone who could not face fifty messages a day. Lists outlived both Usenet and web forums, and plenty of software projects are still run through them.