A mailing list is an e-mail account, such as list@yourdomain.com, used to send out to multiple recipiets at one time. If you have a group of people you want to receive e-mails, rather than adding each name to your e-mail To: line, you can send your e-mail to list@yourdomain.com and the message will be sent to all users on the list. In reverse, if someone sends a message to the list address, it will go to all recipients on the list.