If you use a mailing list to touch base with some or all of the visitors/users on your web site on a regular basis, its subscribers are often referred to as mailing list members. They have to sign up and to express their explicit permission to receive automatic email messages. You can include mailing list members manually too, as long as the program that you use to manage the mailing list permits this. According to the commonly accepted policies, a mailing list member should be able to unsubscribe at any moment. You, being the mailing list admin, can also delete mailing list members if they should not get emails for whatever reason. The messages that each mailing list member receives will have just one address in the "To" section, not the addresses of all the mailing list members.