... will continue to subscribe/unsubscribe using simplenews newsletter module and you will create the newsletters the usual way. The script works with multiple newsletter categories and every time processes the latest newsletter that has not been sent. After you sent the newsletter, there is nothing else you need to do. Nothing very fancy but is good for sending thousands of e-mails.
For more info visit
http://tecorange.com/content/mail-send-addon-drupal-simplenews-newsletter