Newsletter > Newsletter Problem Report
This will show a list of problems that occurred while sending newsletters.
This report enables you to remove the incorrect emails from your subscribers' list.
There aren't many functions you can perform on this page, but it's a useful tool in monitoring how your newsletters are being received and keeping inactive emails from being spammed.
If you use an extension like MailChimp, you will have access to several reports that will help you build a successful newsletter and even generate custom newsletters for customers' based on their activity on your site.
See some report examples from MailChimp here.