GNU Mailman is a mailing list management software. Mailman project was started long time ago before the Millennium. Since its birth it has become the most intelligent tool for handling mailing lists ever. Huge number of companies with Fortune 500 members among them have been using Mailman for years. The new version Mailman 3 brings to us even better user experience and communication power.
WP Mailster - WP Mailster enables you to run a listserv-like email discussion list on your WordPress site.
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.
Listeron - An email address for your group. Discuss. Debate. Organise. All with email.
Sympa - Sympa is an open source (GNU GPL) mailing list management (MLM) software.
Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES
MailChimp - MailChimp is the best way to design, send, and share email newsletters.