Interesting stuff. I've got 2 Hotmail accounts and one GMail account on my iPhones. When I first got the devices, I was uncertain just how to enter the accounts onto the phone. Some said to use Exchange and some others said to enter the accounts manually, using specific server data. I'm not certain what I did, but I think my GMail account was entered using Exchange (whatever THAT is??!!) and I haven't had a problem with it at all. Every now and then I get a message when I turn the iPhone on that my Exchange password is wrong, but I just disregard that and press on. My Hotmail accounts are simply perfect all the time, and I don't think I used Exchange (again, whatever THAT is?!) when I configured them.
I'm curious what will eventually resolve your problem.
Note to self: What is an "orange" server?