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.
Sympa - Sympa is an open source (GNU GPL) mailing list management (MLM) software.
Listmonk - Send e-mail campaigns from a powerful dashboard. High performance and features packed into one app.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES
Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.