microsoft keeps a list of problems: Current issues with Microsoft Exchange ActiveSync and third-party devices
After some problems at a customer i looked deeper at these problems.
Most problems come's with ios devices (iPhone and iPad)
Sow I made a list of al iOS versions (6,7 and 8) and there problems.
To keep this simple i created a powershell script: Block-IOS-Devices.ps1 or you can download it from the Technet Script Libary: Block iOS devices with Block-IOS-Devices.ps1 Script