If the moderator address is not set, it will default to the list-approval address. Provides the sender address for the welcome mail message generated as part of the subscribe command. Appended to the subject line of all messages sent to the list. Can be anything. Open allows people to subscribe themselves to the list.
Auto allows anybody to subscribe anybody to the list without maintainer approval.
Closed requires maintainer approval for all subscribe requests to the list. Open allows people to unsubscribe themselves from the list. Auto allows anybody to unsubscribe anybody to the list without maintainer approval. Closed requires maintainer approval for all unsubscribe requests to the list. The reply includes an authentication number which must be sent back in with another subscribe command.