A Web-based solution offering Webmail & Address Book (free), plus Calendar, Online Docs Space.

The Web2 Communication Solution is a rich solution full of nice features and a large set of interfaces (Ajax-Web2.0, HTML and Mobile). The free version provides Webmail and Address Book for 10 users. Additional user licenses and extension modules are available, for calendaring, online file storage, contact and event synchronization… It runs only on Linux platforms.