Here's a thought that will not help you sleep. "Every time you use your e-mail system," says Nancy Flynn, executive director of the ePolicy Institute, a Columbus, Ohio, consulting firm, "you put your reputation, your financial assets, and your company's future at risk."

Every time is a lot of times--about 130 billion e-mails are sent each day. A recent study found that the average employee spends a quarter of the workday on e-mail. And according to the Radicati Group, a Palo Alto, Calif., research firm, the typical corporate e-mail user handles about 19.5 megabytes of data per day. Those megabytes are a mix of personal messages, spam, and possibly a virus or two. Also company secrets, budgets, client data, and performance reviews. Lawyers joke that the e really stands for "evidence." One in five U.S. companies had employee e-mail subpoenaed in a lawsuit or investigation last year, according to a study by the American Management Association and the ePolicy Institute.

So apart from being fantastically useful, e-mail entails risk you need to manage. Not that you have to know everything that goes on under the hood. That's for your IT staff or an outside service vendor (more on that later). But you do need to know if your system is secure, if it complies with the law, and if it is used in a way consistent with the HR policies that you definitely need to have in place.

What follows is a guide to the biggest e-mail concerns, particularly security, compliance, and archiving. We'll give you tools for building an e-mail policy now, which can save headaches later, and also advice on buying the right system. There's some gearhead jargon involved, but this stuff isn't really about tech. Ultimately it's about protecting your business.

John Fried is a frequent contributor to Inc. He lives in Pittsburgh.

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