Understanding Mailing Lists
by Harley Hahn (© 2000)

A mailing list is a system by which a group of people can have a discussion via electronic mail. The idea is that a person can send a message to one central address. That message is then processed by a program which automatically sends a copy of the message to everyone on the list. Thus, once you join a mailing list, you will automatically receive copies of all the messages that anyone sends to the central address. These messages will be sent to your electronic mailbox.
When you join a mailing list, we say you subscribe to that list. To leave the list -- that is, to stop receiving mail -- you unsubscribe. Although we use the words "subscribe" and "unsubscribe", there is no cost involved. You can join -- and quit -- as many mailing lists as you want for free. However, if you join too many, your mailbox will be flooded with so much mail, you won't have time to read it.
Subscribing and unsubscribing to a mailing list is easy. Each list has a special administrative address. All you have to do is send a message to that address saying that you want to subscribe or unsubscribe. A program (not a person) will read and process the message, and carry out your request.
There are three main types of mailing list systems. They are called Listserv, Listproc and Majordomo. Subscribing and unsubscribing with each is almost the same. The is only one small difference when you subscribe to a Majordomo list (which I will explain below).
Let's look at an example taken from my book Harley Hahn's Internet & Web Yellow Pages. In the "Animals and Pets" section of the book, there is an item called "Horses". One of the resources under this item is a mailing list. Here is the information:

Listserv Mailing List:
List Name: equine-l
Subscribe to: listserv@psuvm.psu.edu


What can we tell about this list?
First, we see that this is a Listserv mailing list, as opposed to Listproc or Majordomo.
Second, each mailing list has a name. The name of this list is equine-l.
Notice the two characters -l at the end of the name. In the olden days before the Internet), it was necessary to know if an name belonged to a person or a mailing list. Thus, mailing lists were given names that ended with -l. The letter l (L) stands for "list". On some systems, this is still the custom. That is why this name, equine-l, ends with -l.
The third piece of information we see is the address to which we would send mail to subscribe. In this case, it is

listserv@psuvm.psu.edu

This is the address of the program that administers the list.
When you send a message to this address, your message is not seen by a person. Everything is done automatically by the Listserv program. It will read your message, figure out what you want, and respond appropriately.
There are many commands you can send to a Listserv program (and the same goes for Listproc and Majordomo). I will describe four.

Getting Information About a Mailing List

Before you subscribe to a mailing list, you should always send a request to the mailing list program asking for information about that list. This will help you make sure you really want to subscribe, as well as alert you to any special considerations about the list. To request such information, send an email message to the administrative (subscription) address. The subject of the message doesn't matter: it will be ignored. In the body (main part) of the message, put a single line consisting of the word info followed by the name of the list.
For example, in this case, you would email a message to:

listserv@psuvm.psu.edu

The subject of the message could be anything. In the body of the message, you would type the single line:

info equine-l

Now wait until you receive an email reply with some information. Sometimes this takes only a few minutes, sometimes longer. When you receive the reply, read the information and see if you still want to subscribe. (There will be a lot of technical information you can ignore.)

Subscribing to a Mailing List

After you find out about mailing list, you can subscribe by sending a one-line message to the same administrative address. This message should have the word subscribe, followed by the name of the list, followed by your first and last names. You do not need to specify your email address. The program at the other end will pick it up automatically.
Let's say your name is Bart Bunzlehammer. To subscribe to the equine-l mailing list, send a one-line message to the address:

listserv@psuvm.psu.edu

The subject of the message doesn't matter. In the body of the message, you type the single line:

subscribe equine-l Bart Bunzlehammer

When the message is received, the Listserv program will automatically subscribe you to the list. From now on, any messages sent to the list will be sent to you as well.
Hint: For security reasons, some mailing list programs require you to confirm that you really want to join the list (just in case some friend has snuck over to your computer while you were away and sent in a subscription to a mailing list). If this is the case, you will be sent instructions on how to confirm. Usually, it is as simple as replying to a message and saying "ok".

Unsubscribing to a Mailing List

You can unsubscribe to a mailing list at any time. Just send a one-line message to the administrative address with the word unsubscribe, followed by the name of the list. You do not need to include your name or your email address. In our example, you would send a message to the address:

listserv@psuvm.psu.edu

The subject of the message doesn't matter. In the body of the message, type the single line:

unsubscribe equine-l

For a Listproc mailing list, everything works exactly the same. For a Majordomo mailing list, there is only one difference: when you subscribe, you do not have to specify your first and last name.
The final command I want you to know about is help. Listserv, Listproc and Majordomo systems have more commands than info, subscribe and unsubscribe. To learn about these commands, send a one-line message to the administrative address with the single word help. For example, you can send a message to the address:

listserv@psuvm.psu.edu

The subject of the message doesn't matter. In the body of the message, type the single line:

help

Once you belong to a list, the question arises, how do you send messages to everyone on the list? You do not send messages to the administrative address: that is only for subscribing, unsubscribing and so on. Rather, you send messages to the list itself. The list's address consists of the name of the list, followed by the name of the computer.
In our example, the name of the list is equine-l. The name of the computer is psuvm.psu.edu. Thus, to send a message to the list itself (that is, to all the people on the list), you would mail to:

equine-l@psuvm.psu.edu

Each time you send a message to this address, it will be sent automatically to everyone on the list.
So remember, when you want to unsubscribe, do not send the unsubscribe message to this address. All administrative requests go to the administrative address (where they are handled automatically by a program).

Summary

For reference, the following summary covers what I have explained in this article. (Notice that, with one exception, all three systems -- Listserv, Listproc and Majordomo -- work the same. The exception is: when you subscribe to a Majordomo mailing list, you do not specify your first and last name.)

To request information about a mailing list, or to subscribe or unsubscribe, send mail to the administrative (subscription) address for the list. For example:

listserv@psuvm.psu.edu
majordomo@massey.ac.nz
listproc@cornell.edu


To request information about the list, use the command:

info listname

To request general help information, use the command:

help

To subscribe to a list with Listserv and Listproc, use the command:

subscribe listname firstname lastname

To subscribe to a list with Majordomo, use the command:

subscribe listname

To unsubscribe to a list, use the command:

unsubscribe listname