SendPress: Email Marketing and Newsletters is a WordPress plugin by brewlabs that sends emails and newsletters. Instead of focusing on providing every single feature under the sun, SendPress tries to provide only the ones that you really need. It aims to make email marketing through WordPress easy, complete and extensible. There are free and premium versions.
Simple editor. With an html-free experience
Easy to use theme styler with ability to create a default style
Stat tracking for each email: clicks, opens and unsubscribes. Bounce handling and report details with SendPress Pro.
Add a subscription form as a sidebar widget or in your pages
Send with your web host or Gmail for free (Mandrill, Sendgrid, Amazon SES and more with PRO).
Developer friendly with dozens of actions and filters
Scheduled Sending of emails
Sync Lists to WordPress Roles
More information at SendPress.com.