I have been using Mailstreet to host my Exchange service. They have been absolutely excellent. I have used them with my BlackBerry, iPhones, Nexus One, and my HD2. They have all been excellent with Mailstreet.
I used for many years Mail2web : I was very satisfied, support more or less ok.
Until I recently switched to Exchangemymail and realized how good and super fast their support is.
Also their server seems MUCH more faster.