Mailing list - An E-mail-based discussion forum dedicated to a topic of interest. An interested Internet user can subscribe to a mailing list by sending an e-mail message that contains appropriate instructions to a specific e-mail address. The computer that houses the mailing list program maintains a list of subscribers and routes all posted messages to subscribers' electronic mailboxes. Mailing lists are either publicly and privately maintained, and can either be moderated or unmoderated.