While enterprises may benefit from Microsoft's unified communications software, smaller businesses are unlikely to see a return on their investment, according to new research released today.

The study, carried about by Ferris Research in San Francisco but commissioned by Unison Technologies, found that it could cost smaller businesses as much as £120 per user per month to deploy and operate a Microsoft-based unified communications infrastructure.

These costs fell to £40 per user per month for 500 staff, and £20 for 5,000 staff. The scenario covered the latest versions of Office Communications Server 2007 in combination with Exchange Server 2007 and a third-party PBX system.

"While these costs are more affordable for larger enterprises, SMBs may find it difficult to justify the investment especially at a time when IT budgets are under greater scrutiny," said Ferris Research president David Ferris.

Unison develops rival technology that combines the PBX, email server, instant messaging and directory services into a single server.