One of the best ways to reduce costs and to increase productivity in the SMBs is by introducing information and communication technologies (ICT). And the statistics of recent years, that show over 50% annual growth in the adoption of ICT solutions depending on the segment, support this fact.
In this context it seems reasonable to consider Linux as a more than interesting SMB server alternative, since technically it has shown very high quality and functionality and the price, free, is unbeatable.
Zentyal (formerly eBox Platform) was developed with the aim of bringing Linux closer to SMBs and to allow them to make the most of its potential as an enterprise server. Zentyal is the open source alternative to Windows Small Business Server, based on the popular Ubuntu version. Zentyal allows ICT professionals to manage all network services such as Internet access, network security, resource sharing, network infrastructure or communications through one single platform.
Zentyal 2.0 is available for download at: http://www.zentyal.org/download/latest
The official Zentyal 2.0 release announcement is available at: http://trac.zentyal.org/wiki/Document/Announcement/2.0/
You can check zentyal features from here
You can check here for installation.