Drupal Simplenews Mass Subscribe
Simplenews is a quick and easy way to set up and manage newsletters on Drupal, but if you add it to a site which already has users, you might want a way to quickly subscribe all your users to your newsletter.
Rather than click through all users and manually subscribe them - which can be a little bit boring if you have thousands of users - you can run a few SQL queries to mass-subscribe everyone in one go.