This causes problems for users. Go through the other options. It may be an idea to print out the settings so that you can return them to the original settings once you have perused the options. In this section you can make your list open to all subscribers, closed to members of an association or club. You can also set who can obtain a list of member's e-mail addresses.
Some lists require the subscriber to confirm that they want to join.
The default for our lists is not to require this. The administrator can moderate lists. This is good for student lists. Do you want non-members to be able to post to the list. We would recommend that the answer is no to avoid unsolicited e-mail.