Simplenews Scheduler sends a newsletter as a re-occurring item based on a schedule.
It does so by creating a new edition
(rendered copy as HTML Format) of a node at the time that it required to be sent again. The editions have an extra tab (for those with permissions) for viewing all editions as well as the original newsletter they are generated from. The original newsletter is never sent but all editions are according to a pre-defined schedule which is triggered via cron and can be defined when you create or edit a simplenews node. Current options for sending are by day, week, and month.
Works great with Insert View to place the content of a view into a newsletter. (eg: [view:recent_articles=20])
An early Drupal 8 port is available. The Drupal 7 release is considered stable. It is recommended to use simplenews 6.x-2.x branch along with the 6.x-2.x release of this project for sending scheduled newsletters.