A mailing list is a list of email addresses which get the very same email simultaneously. When you send a message to the mailing list address, your message will be redirected to all the addresses on that list automatically, but none of the receivers will become aware of who the other recipients are. In the general case, people have to join a list, but sometimes mailboxes are added manually without their owners’ consent. Depending on the concrete list management software, you may also be able to add new mailing list subscribers, so people will not be able to subscribe to your mailing list unless you authorize their request. The mailing list option is extremely handy if you want to send newsletters on a regular basis or some other type of periodic notifications to customers, since you will have to send a single e-mail message and all the subscribers will get it instantaneously. As a consequence, you won’t need to insert a huge number of email addresses manually.