Great article on the Exchange team blog from mobility guy Adam Glick: it’s all about how to block classes of devices that you don’t want connecting to your Exchange server. You can already turn Exchange ActiveSync on and off for individual users, and you can allow or deny individual devices for those users. However, those solutions are best if you want to block a known-bad user or a known-bad device. If you want to block, say, all iPhones (or all BlackBerry devices, or all Nokias, or whatever), Adam outlines an easy solution for doing so.