Techniques need to be used to limit "apparent authority" with personal use of corporate systems. A disclaimer could be required for personal mail. Or, conversely, a disclaimer could be mandatory except when the employee designates that it is business mail. This would require companies publish and train users on the definition of business mail, as well as acceptable use policies. Of course, with the Hatch Act, partisan use of White House computers would probably not be a good idea.

A company must also decide whether to permit the use of Web-based or other personal email systems. The problem is that there is no way to prevent employees from using such systems for business mail. Language based filters to detect personal mail, such as the one from my company, InBoxer, are good -- but far from perfect. For example, is it personal or business mail to invite a neighbor, who may become a customer, to a baseball game?

Whatever is decided, be prepared to enforce it uniformly. In a recent Virginia case, a newspaper had a policy that prohibited personal use of corporate email system. According to the case (Richmond Times Dispatch v National Labor Relations Board, March 15, 2007), it was first enforced when employees were organizing a union. Selective enforcement was not allowed.

Roger Matus is an expert on email archiving and retrieval. He is the CEO and co-founder of InBoxer, Inc., has been in the software business for about 25 years, and worked on the development of an email product back in 1983. He's spent much of the past decade working on speech and language technology in business applications and has recently begun to use his language technology to create a smart email archiving system.