Backchannel Chat - Backchannel Chat is best in class discussion tool that is intended for teachers to streamline their class activities.
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.
Flowlingo - Get fluent in a language through content immersion
Mailman 3 - Dedicated Mailman 3 installation. Unlimited lists/configuration. Free subdomain at mailman3.com. Dedicated support for list admins.
Eduflow - Digital learning that actually teaches students something
MailChimp - MailChimp is the best way to design, send, and share email newsletters.