I've searched a little and I needed to add newsletter functionality to a Drupal 7 installation. I've found Simplenews, which is in Beta version for Drupal 7 nothing more. I don't need anything really complicated, just these functionalities:
- Guest user can subscribe to newsletter by leaving their email address in a field
- Registered users can tick a checkbox in their profile to choose whether to receive newsletters
- Users can unsubscribe from newsletter by clicking a link in the newsletter
- A WYSIWYG editor for sending newsletters (but, I think this can be accomplished with the WYSIWYG module)
nothing more. If any of you tried the development version of Simplenews, please provide your experience.