There is Zimbra Groupware for the enterprise. also there is one more choice: Citadel Groupware

Citadel Groupware is a turnkey open-source solution for email and collaboration. One simple installation delivers a multitude of powerful features, including:



address books

bulletin boards

mailing list server

instant messaging


multiple domain support

a powerful web interface

The web server/Mta are all tagged with Cit, of course you can change web server to Apache. it support spam and anti-virus.

very easy install step on Ubuntu

sudo apt-get install clamav clamav-milter spamassassin citadel-suite amavisd-new -y

then goto http://urip/ to test

Official site: