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Following the availability of Service Pack 3, released on June 20th 2010, Microsoft Exchange Server 2007 can now be installed on Microsoft Windows Server 2008 R2.
Note: It is important to note that prior to installing Service Pack 3, you will be required to install an update for the CDOex component, as described in Microsoft KB article 982720. The CDOex component is used by GFI FaxMaker Message Transfer Agent service.