Listservs are a Variation of e-mail. When users interested in a particular topic subscribe to a listserv on some topic, they begin to receive messages from the other members of the list. To get a message to all of the list's subscribers, a user sends a single copy of the note to the list, and the Computer that hosts the list sends a copy to all subscribers. The sender generally does not even know how many nsers there are, let alone who they are.

Lists often have hundreds of subscribers, and listserv participation sometimes results in e-mail inboxes choked with messages. For this reason, some lists are "moderated," which means that one or more people read the message before it is copied to all members of the list, to determine whether it is worthy of distribution. For the same reason, membership on some lists is restricted. Other lists may group messages that are sent periodically in one e-mail as a "digest" instead of sending many individual messages.