As per the first comment on this issue I was able to correct this issue by changing the inheritable permissions. But to access the security tab on the active directory user you first have to select "view > advanced features" under active directory. See EV100414
(Exchange ActiveSync Returned an HTTP 500 Error).
In my case, I had to go to the User in Active directory, and under Security, Advanced I had to make sure Inherit from Parent Object was checked. Once I did that, the email started flowing without issue.
This warning occured after a user came to me saying his iPhone was retreiving mail very slow. My warning was giving me the explanation below:
--- Exception start ---
Exception type: System.Web.HttpException
Exception message: Maximum request length exceeded.
Exception level: 0
Exception stack trace: at System.Web.HttpRequest.GetEntireRawContent()
--- Exception end ---.
Ended up happening because he was trying to send an e-mail from his iPhone with an attachment that was too large (9MB). The message was hanging in his Outbox on his iPhone, but not in Outlook. Deleted the message in his Outbox on his iPhone and all was fine.