I use Samsung Galaxy Note with Android 4.0.3. When I am outside the home network i.e. On roaming, the phone is not able to sync with Microsoft Exchange. When I am back in Home network they get downloaded.
Also even in home network the email exchange is not stable. Many a times you get message "Update security settings".
I have contacted our IT Help-desk which says that settings are correct. The mobile service provider says that as other net based applications are working the problem is not at their end.