If you've been clinging to the interoffice email and calendaring capabilities of Microsoft Exchange as your company's last vestige of proprietary software, it's really time to consider giving up the ghost.

Open source collaboration software vendor Open-Xchange, Inc. announced recently it now offers its flagship product, Open-Xchange, as an appliance edition in addition to its server and hosting versions.

Like Microsoft Exchange, it's got email, calendaring, document sharing, contact management, and a backup and recovery system. Unlike Exchange, however, it doesn't come with a hefty price tag. Most deployments cost in the area of only $70 per user, per year.

Exactly how much a company can save by implementing Open-Xchange over Microsoft's counterpart is a matter of debate, though three-quarters of a million dollars isn't completely out of the question.

Open-Xchange Appliance Edition, aimed at small and medium-sized businesses, is designed to be a turnkey option for companies that want email and document server capabilities but don't have an army of IT gurus to set up the technology.

Out of the box, Open-Xchange Appliance Edition comes complete with "a fully-supported Debian-based Linux, along with Samba file and print services, and software connectors for Microsoft Active Directory to facilitate user and group administration, as well as integration into existing IT infrastructure." It also supports VMware and Xen virtualization technologies.

In case you need more of a reason to give Open-Xchange a try, consider this. The company recently announced it has secured $9 million in Series B venture funding. According to a prepared statement, the company intends to "use the funds to further develop its software and continue expanding its business in the U.S., Europe and emerging markets."

Through various deals with hosting companies like 1&1 and Network Solutions, Open-Xchange currently has well over 8 million paid mailboxes. Company CEO Rafael Laguna says plans include the addition of 10 million more by next year.

At a time when analysts are predicting venture capitalists will move away from funding open source projects, at least three venture capital companies are willing to back Open-Xchange's horse.

Is your company thinking of switching from Microsoft Exchange to Open-Xchange or another open source collaboration suite? Tell me about it in the comments.