GroupServer is an open-source collaboration server, licenced under the GPL. Like Yahoo! Groups and Google Groups, it allows people to hold many-to-many and one-to-many conversations using email and the web.
The email interface to GroupServer is like a mailing list: people send a message to the email address of the group, and the message is relayed to all group members who want to receive it. The web interface of GroupServer provides a secure and personalised interface like an online message board with member directories, postings by topic, Web Feeds, document sharing, advanced searching, and Web-based forum management and many other features.
GroupServer is designed, developed and sponsored by OnlineGroups.Net, who provide hosting, consulting and support for GroupServer installations.