If you use a mailing list to get in touch with some or all of the visitors/users on your site on a periodic basis, its subscribers are often referred to as mailing list members. They need to subscribe and to express their approval to get automatic emails. You can authorize mailing list members manually as well, on the condition that the mailing list client app that you make use of to manage the list allows this. According to the generally accepted policies, a mailing list member should be able to unsubscribe whenever they wish. You, as the mailing list admin, can also delete members if they should not receive emails for whatever reason. The emails that each member receives will have just one single email address in the "To" field, not the addresses of all the mailing list members.