### 2.7.1 Subscription rules

This subcategory controls the rules for exposing the existance of this list, and for what new members must do in order to subscribe to the list.

advertised
  This option controls whether this list will show up in the list overview for the site. Normally, an overview contains the name and short description of every mailing list in the virtual domain. By setting this variable to No, it will not show up in this overview, nor will it show up in the administrative overview. The only way then to find the list is to guess (or know!) its name.

subscribe_policy
  This option controls the steps that a new member must take to join the list. The available options may differ based on some defaults that the site administrator chooses. They are:

  - None - No verification is done on the subscribing member. This is also called open subscriptions and is generally disabled by default. The site administrator must allow list admins to choose this option; if not, this option will not be presented to you.

  - Confirm - An email confirmation step is required before the address is added to the list. When a member requests subscription, either via the web page or by sending a message to yourlist`-join@example.com`, Mailman will send a confirmation message to the requesting address. This mail-back confirmation contains a unique identifier, which the requester can present to Mailman in order to confirm their subscription. This can be done either by replying to the mail-back, or by visiting the url in the mail-back message. The url points to a page that lets the user either discard or confirm their request.

  - Require approval - All subscription requests are held for approval of the list moderator. No mail-back confirmation is sent, but the list admins will recieve a message indicating that approval is pending.

  - Confirm and approve - Here, a mail-back notice must first be confirmed by the requester. Once confirmed, the list moderator must then approve the request. This is the most secure method for users to subscribe since it both verifies the requesting address, and forces the list moderators to approve the request.

unsubscribe_policy
  Specifies whether the list moderator's approval is required for unsubscription requests. No is highly recommended, since it is exceedingly impolite to not allow people to leave a mailing list whenever they want (i.e. opt-out). Yes is useful in some specialized contexts; e.g. you may not want to allow employees to unsubscribe from the company newsletter.

ban_list
  This contains a list of addresses (or regular expressiosn), one per line, that are banned from ever subscribing to your mailing list. If a match occurs during the subscription process, the request will be automatically rejected, and the requester will get a rejection notice. You can use this to permanently ban troublesome posters to a members-only list.

private_roster
  This specifies who is allowed to view the roster of member addresses. If you choose Anyone, then the list membership is completely public. You can limit exposure of the roster to just list members, or just to the list administrators. In the former case, a user must enter a valid member's address and password before they can view the roster. In the latter case, a list administrator's password must be enter; if a matching admin password is entered, address field is ignored.

obscure_addresses
  Controls whether some simple obfuscation of addresses is used when member addresses are included on web pages. This should reduce the opportunity for email address harvesting by spammers, although it probably doesn't eliminate it.