Way to send e-mail automatically to many people on a regular basis. Most are organized around an area of interest.  Mailing lists give you access to the pre-installed Mailman Mailing List Software. Large mailing lists, (those exceeding 500 subscribers) sent using the HQ Secure Services, must be sent using the mailing list tools that have been pre-installed for this purpose. Mailman is free software for managing electronic mail discussion and e-newsletter lists. Mailman is integrated with the web, making it easy for users to manage their accounts and for list owners to administer their lists. Mailman supports built-in archiving, automatic bounce processing, content filtering, digest delivery, spam filters, and more.

Mailman Mailing List Home: http://www.gnu.org/software/mailman/index.html