Wikipedia
GroupServer is a computer software application from OnlineGroups.net for managing electronic mailing lists.
GroupServer is a Web-based mailing list manager designed for large sites. It provides email interaction like a traditional mailing list manager but also supports reading, searching, and posting of messages and files via the Web. Users have forum-style profiles, and can manage their email addresses and other settings using the same Web interface. It supports features such as Atom feeds, a basic CMS, statistics, multiple verified addresses per user, and bounce detection, and is able to be heavily customized.
GroupServer is coded primarily in Zope and Python and currently maintained by OnlineGroups.net. GroupServer is free software, distributed under the GNU General Public License.