Where do you report Email Fraud?

I recently received email regarding stock that will be “bought out” or stock that has a “special merger.” I suspect that this is a scam designed to drive up the price of the stock. I suspect this because it came from unsolicited from someone I do not know. It also had an invalid return address. To me, this is clearly fraud and should be reported. The question is: To whom should it be reported and how do I report it?

Here is a link to the Postal Inspector of the USPS. The Enforcement Division of the Securities and Exchange Commission may also be interested.