I'm going to be implementing exchange 2010 soon. I want to setup a redundant email server. Can I be running Exchange 2010 standard on the backup box (on Windows 2008 std 64bit)? My primary server will be a 2010 enterprise box. I'm not looking for active/active, just a hot spare. Some stuff I read just says the Windows 2008 needs to be Enterprise (I get that since it uses windows clustering). But some says you have to have Exchange Enterprise and some does not specify that.