Module are commonly used for newsletter solutions in Drupal is Simplenews, very cheap since Simplenews sending the email from your own server. But what if the number of subscribers reached more than 10.000 people? would be very aggravate your server if you sent it from your server.
In addition Simplenews module, there is also another excellent module like MailChimp. MailChimp module provides integration with the MailChimp email delivery service. But the free version is limited to 2000 subscribers and must not exceed 12.000 emails per month.
MailChimp is worth your consideration if you need a newsletter solutions that is different from Simplenews.