
You need to figure out the difference between the test user and the actual user, which is likely to boil down to permissions. Checking OWA from an iPhone is for all intents and purposes, not different from checking it in a Web browser.
Mobile devices typically do not handle certificate errors very well. You certainly will not be able to click around it using WM based devices. You need to resolve this by ensuring that the root CA is trusted and that the URL used to connect to the Exchange Server is the common name used in the certificate.
Check accessibility from other mobile devices as recommended by Labnuke regarding the Exchange ActiveSync issue. This will let you know if it is device or system related.

This sounds similar to what we ran into, but this helped:
http://bluescreensolutions.blogspot.com/2010/01/how-to-make-iphones-work-with-exchange.html

I believe you need to have an SSL Cert installed on the Server in order for the IPhone to receive emails with Exchange

















