@PopeDai:Yes, I was actually being flippant, and simply making a general point that as Exchange and Outlook versions get further apart, the ability to support them becomes more difficult, as newer tech is implemented and older tech is phased out.

Generalizing (and dependent on your requirements) this works both ways... newer Exchange gradually drops support for older Outlook, and newer Outlook gradually drops support for older Exchange (e.g. Office 2010 won't support Exchange 5.5)