a program that sends and receives messages for subscribers of an e-mail discussion list.
Though a list may be moderated, the actual list of subscriber email addresses is likely managed with specially designed software called a list server. The list server receives and responds to email commands for subscribing and unsubscribing, as well as other commands that may be more complex. It will also deliver the email publication to the list at the request of the list manager. Each list server requires its own precise set of commands for each task. There are several popular list servers that manage many of the email lists in publication today; examples include: Majordomotm and ListSERVtm. It is also common for large list hosts to own their own proprietary software to run the lists they host.
Strictly speaking, a computer program that administers electronic mailing lists, but also used to denote such lists or discussion groups, as in "the writer's list server."