Information
This control determines if new passwords are required to satisfy a certain level of complexity. By default, iOS devices do not enforce a passcode complexity policy, and the default Exchange ActiveSync policy setting applied for users not assigned to a mailbox policy does not require an alphanumeric passcode. The recommended settings are enable alpha-numeric device password.
Solution
From the MobileIron console, open the Policies and Configs -> Policies view. Under the Security Policy verify that Password Type is set to Alphanumeric.