When sending a message to the program, think of it as talking to a computer. Although they are all cousins, the computers may understand a slightly different command language. The computer needs to be sent a very specific message or it cannot respond with anything except a standard error message. Don't worry about making the computer upset with your mistakes. Computers are very forgiving.
Computers are more forgiving than some of the subscribers to the list.
There are several places you can find the name and address of hundreds of current listservs. You will receive a list of several hundred listservs. Listserv, listproc and mailserv work basically the same way, differing primarily in what you call the computer. It is important to remember that the next three computers work differently. Many relevant discussion groups can be found on them, but people who are familiar only with listservs seem to have a terrible time canceling their subscriptions.