PHPlist
phpList is an open source mailing-list and newsletter application.
PHPlist is a web application that implements a personalised mailing list manager or customer relationship management (CRM) system.
PHPlist is designed to assist you to stay in touch with your audience, without flooding them with information they don't want. PHPlist is an essential tool for anyone who is serious about creating, capturing and maintaining an offline audience, and will help you increase traffic to your website.
-PHPlist developer