Here's an interesting question for you: if you set up a rule in Microsoft Outlook to forward messages from one account to another, and you do it without the knowledge of the owner of the account you're forwarding from, are you intercepting or merely copying mail? It may seem like a moot point, but for David Szymuszkiewicz, a former IRS worker, it's an important distinction. David was afraid of being fired after his license was suspended for drunk driving (he needed to drive to the homes of delinquent taxpayers), so he secretly set up this rule on his boss's machine to see what the world was saying about him. The rule was discovered and, wouldn't you know it, he was in trouble. The only question now: whether to charge him under the Wiretap Act for intercepting messages or the Stored Communications Act for merely copying of them.
So, what was your answer to the question above? You might be tempted to say he was simply making a copy, and indeed that was Szymuszkiewicz's argument, but any Exchange admin will tell you that Outlook rules are executed on the server, not at the client, meaning those e-mails were indeed being intercepted. Szymuszkiewicz was convicted of wiretapping but seems to have avoided a harsh sentence, with 18 months probation being handed down. A light punishment for wiretapping, but a heavy one for diddling menus in Outlook.