WP Mailster - WP Mailster enables you to run a listserv-like email discussion list on your WordPress site.
Listmonk - Send e-mail campaigns from a powerful dashboard. High performance and features packed into one app.
Listeron - An email address for your group. Discuss. Debate. Organise. All with email.
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.
Mailing Group - Listserv - Allows you to run a free Listserv or email group right from your WordPress dashboard.