Exchange iApp 1.3.0 and disconnection of Entourage 2008 EWS

I'm not sure if this would help with your problem, but one of the things we noticed when we were setting up Exchange 2013 is that there are some extra steps that need to be taken to get things working properly (at least for us). I'm not sure if you've looked at the deployment guide, but I know we had to add some additional iRule stuff to get everything working appropriately. It may be worth taking a look at to see if it can help at all.