My first reaction to this email was that this is just another crazy Internet rumor. I mean, if President Obama didn't really go to Columbia, wouldn't it have come out during the campaign? So I did a little research and here's what I found.
If Obama's classmates don't remember him, it might be because he only attended Columbia for two years before graduating. He transferred from Occidental College in California before his junior year. At Columbia, he lived off-campus. He also spent most of his time studying. "Mostly, my years at Columbia were an intense period of study," Obama told Columbia College Today in 2005. "When I transferred, I decided to buckle down and get serious. I spent a lot of time in the library. I didn't socialize that much. I was like a monk." Read the whole thing here:
Columbia College Today
Moreover, one of Obama's professors at Columbia remembers him well. Michael Baron told the New York Times that he wrote Obama a recommendation for law school. (In the same interview, Baron inadvertently fueled another Internet rumor about Obama's "fake thesis.")
http://www.nytimes.com/2007/10/30/us/politics/30obama.html?_r=1&pagewanted=2
PolitiFact | Obama's Columbia 'thesis' is all fiction, dreamed up by blogger
Finally, it should be noted that the source of this rumor is Wayne Allyn Root, who was the Libertarian nominee for Vice President. He made similar claims in an interview with Reason magazine, saying that "maybe" Obama "was involved in some sort of black radical politics." Clearly, Root has political motivation to try to make Obama look bad.
Wayne Allyn Root's Million-Dollar Challenge - Reason.com
Hopefully, this will help clear up your concerns. If anybody sends you another email like this, make sure you get the facts before sending it to more people. That way people won't get all worked up over nothing.