Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.
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My answer is a starting point, since you didn't say:
1. Where you want to back them up to (i.e. local server drive, consolidated on one of the local workstations, etcetera)
2. If you have a local file / print server to backup to ...
3. Cloud / offsite / local USB drives on each computer ...