A listserver is a program that maintains one or more of these mailing lists. It automatically distributes an e-mail message from one member of a list to all other members on that list. When you subscribe to a list, your name and e-mail address is automatically added to the list. Should a private message to a member of the list be desired, all one has to do is reply to the individual who posted a message and NOT to the list. It should be noted that more than one embarrassment has arisen out of errant messages.
Most lists are public in the sense that anyone can join.
Not all those who join a list actively participate but rather simply read the postings made by others. This frequently occurs when one is newly subscribed and tries to determine the tone of the list. In this case, it is not possible to subscribe to the list in the normal way. Only the Administrator of the Listserver can subscribe you. Such an arrangement can be worked out between individual groups and an Internet service provider.