Employees who understand that their e-mail might be monitored will, if they value their jobs, be less likely to use it inappropriately. Begin with an official policy stating that company e-mail is for business use, not personal, and that e-mail messages are subject to random monitoring. In a memo or training session, explain the reasons for the policy. You can even give your employees a daily reminder by having a statement of the policy appear on the screen every time they log on to their computer. If they've just been reminded that their boss might read their e-mail, they'll be less likely to send out inappropriate messages.
The law in this area is murky enough that e-mail could be construed as the equivalent of a telephone conversation, and some states require permission before listening to an employee's phone conversation. Accordingly, Shear advises obtaining employees' consent to monitor their e-mail every time they log on to the system. At the end of the on-screen policy reminder, inform employees that by proceeding to use the system, they've given their consent to have their messages monitored. Those who want privacy--to the degree it's obtainable for electronic communication--can sign up for e-mail at home.