This is Mailman 3 software delivered as a service with pay-as-you-go billing scheme.
What is Mailman?
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.