as I said previously
test the newsletter first by sending one edition to yourself as the only subscriber.
then you can subscribe all site members to it by clicking a button.
then when you send it it will go to all site members email addresses
the user who receives the mail can click the unsubscribe link but they will have received this message
keep in mind that the site members did not choose to subscribe to the newsletter so you could either delete the newsletter or unsubscribe everyone after the message has been sent or make your own decision whether you want to keep the newsletter around after that.
usually newsletter is a marketing tool but in this case it isn't really a marketing message that you are sending out, this is just using it because it is a convenient way to email all site member email addresses.