Today I stumbled across some weird stuff where one individual account wasn't able to synchronize on their iPhone/Droid. They would sign in and get an error saying the "Connection to the server was unavailable."
To fix this, simply follow the steps below! 🙂
Open Active Directory Users and Computers -> View > Advanced Features.
Find the user with the problems connecting, Right-Click -> Properties.
Click the Security tab -> Advanced and make sure that the check box for "Include inheritable permissions from this object's parent" is checked.