Mailing lists enable powerful one-to-many communications.
Because mailing lists are based on email, they share the key features of email. Mailing lists also build on that technology to create a new capability called “one-to-many” functionality, enabling one person to communicate with many people at the same time. This feature is a virtual Internet extension of the real-world communication power of a person speaking to a group, except that the members of the audience may be located anywhere in the world.
The reverse is also true: mailing lists can give one person unique access to the informed opinion of a diverse group of people on various subjects with little effort — the email arrives from the groups they have subscribed to, and they then read the ones they want.
Like so many of the Internet technologies, mailing lists are important primarily because of their power to bring people around the world together in a single communication setting.