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Electronic mail is still the most-used service in the Internet, and not the WWW, as one might expect. It is used for casual conversations between people all over the world, for discussions of all kind of topics, for transmitting data files through the net or for distributing information amongst colleagues in a world-wide company. Even in Intranets electronic mail is very useful, because it is quick, easy to archive and reliable.

Electronic mail is not limited to conversations between only two peers. A mail may have several recipients unlike a paper letter. Hence, discussions between groups of people can be held with this media easily. Everybody sends the mail to all persons involved in the discussion and everybody can reply in a way that all others see his text, too.

For larger groups of people, though, this becomes inconvenient. When exchanging e-mail in a larger group of recipients, people tend to accidently forget persons in the list of recipients, they send their replies to the wrong person, they have to keep their aliases up-to-date for the mail to reach the person, etc...

To remedy these shortcomings, the idea of the mailing list was developed. A mailing list is hosted on a central server, which has the addresses of the people who are on that mailing list. Then a special account is created, called the mailing list address, to which people can send the mail they want to be distributed to all receivers.

The Mailing List Server

The machine accepts the mail, looks up the list of addresses in the list, and re-sends the mail to all those people. If one of the persons on the list wants to reply to a mail he or she has received via the mailing list, he or she sends the reply to the mailing list address again and it is automatically distributed among all recipients again.

The list of addresses on the machine hosting the mailing list is called the list of subscribers and a person who is on that list is consequently called a mailing list subscriber. The process of sending an e-mail to the special address with the intention to get it distributed to all subscribers is called posting to a list.

Advantages of "mailing lists"

The advantage of this setup is that each subscriber only has to know the address of the mailing list and not all the addresses of all the subscribers. In fact, a subscriber doesn't even have to know who is subscribed to the mailing list at all.

Imagine the company you're working for would have a mailing list where all employees are subscribed with their current e-mail address. The mailing list address would then be, say, ``all-employees@enterprise.com". If you'd like to inform all your colleagues about an important happening, you'd simply send an e-mail to that address and everybody would receive it. If a person leaves the company, or a new employee comes to the company, only the list of subscribers on the mailing list server has to be updated and everything would work fine.

Basically, this is what a mailing list server does: It is nothing more than a program that stores a list of addresses, receives mail under a special mailing list address and then re-sends the mail to all subscribers.