I setup and tested Mobiles for various users before deploying on site.
To avoid permission issues we set all the users to "Domain Admins" when on site.
Found mobiles can't connect !
Tried connectivity analyser & did a quick search here
"Exchange ActiveSync returned an HTTP 500 response (Internal Server Error)."
Found this http://technet.microsoft.com/en-us/library/dd439375%28v=exchg.80%29.aspx
"Make sure that the check box for "Include inheritable permissions from this object's parent" is selected."
but I can't see the checkbox !! [I am using Windows 2012 + Exchange 2013 so may be in different place]
On the advanced Tab there is Enable Inheritance but that says its going to make 55+ change and may be slow - so I cancelled...
** Thought I'd check here first !
If I create a New account - I can access the account on the Phone.
JK