Exchange Server 2007 will no longer be supported on the latest Windows Server. The company’s decision may force users to upgrade to the 2010 version of Exchange Server.
Today, at Berlin Germany, Microsoft delivered Exchange Server in a conference. This version has a universal inbox and an improved productivity of 20 percent as well as 70 percent of “cost savings”.
“If we cannot meet our mandate of using the same OS for all servers and a standard collaborative mail server architecture from Microsoft, then we will have to look at other offerings,” wrote Derek who is a customer of Exchange 2007.
Source: Channel Register

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Lee
You might want to reread the article. They are allowing Exchange 2007.
“Microsoft’s reversed its decision not to support Exchange Server 2007 on its latest Windows Server, potentially forcing users to upgrade to Exchange Server 2010 released today.
The three-year-old edition of Microsoft’s email and collaboration server will now run on Windows Server 2008 R2, released last month. Microsoft cited feedback from customers interested in “streamlining their operations and reducing administrative challenges.”
I agree with Cody,
MS has done an about face on the support of Exchange 07 on Server 08R2
There are several articles about this decision, but they all go along the same path about the co-release of Server 08R2 and Exchange 2010 co-releasing and the ability of customers to remain at the Exchange 07 functional level