For example, if you're using a list to enlarge classroom discussion, you might want to use a closed list so only class participants may join. On a public list, anyone who sends a subscribe message for your list is added to the list automatically. An advantage of this method is that it doesn't require any time or energy from the list owner. The disadvantage is that the list owner loses control over who can join the list's discussions. The listserver software can keep old postings in an archive .
Subscribers can send a command to listserv to get former postings.
Archiving the list doesn't require effort from the list owner unless the list is moderated. Most electronic mail systems have some sort of reply command that automatically enters the sender's e-mail address when a response is made to a message. Most systems automatically send replies to the e-mail address that sent the original message. Unless everyone on the list is likely to have the same specific problem, the answer won't be of interest to everyone. If your list is primarily for sending information out to a group rather than for generating discussion, you might not want to have replies sent to the list.