Electronic mailing lists are a special usage of email that allows for widespread distribution of information to many Internet users. Software is installed on a server which processes incoming email messages, and, depending on their content, either acts on them internally or distributes the message to all users subscribed to the mailing list. Popular examples of mailing list software include GNU Mailman, LISTSERV and Majordomo. Today, mailing lists are most often used for collaboration on various projects and as a way of distributing current news and other such information.

One very popular mailing list is Bugtraq. Sometimes these take the form of what is termed a "discussion list": a subscriber uses the mailing list to send messages to all the other subscribers, who may answer in similar fashion. Thus actual discussion and information exchanges can happen. Mailing lists of this type are usually topic-oriented (for example, politics, scientific discussion, joke contests) even if the topic can range from extremely narrow to "whatever you think could interest us". In this they are similar to Usenet newsgroups and share the same aversion to off-topic messages. The term discussion group encompasses both these types of lists and newsgroups.