I have a drupal site which have some content type like article, stories. I want to send the teasers of all posts posted within a week to the subscribed users. It will be a weekly newsletter.
Currenty, Simplenews sends individual newsletter for each node on cron run.
I use Simplenews module with Drupal 7.
You can create a custom module or use Views + Rules + VBO. (if you want not use VBO, see the views_rules module.)
For the scheduling with UI see the simplenews_scheduler module.