Exchange 2007+
See : http://technet.microsoft.com/en-us/library/bb123548.aspx, and http://searchexchange.techtarget.com/generic/0,295582,sid43_gci1305153,00.html and http://www.biztechmagazine.com/article.asp?item_id=581&c=59&n=servers
Working for cloudficient.com