Information
Disable installation of apps from unknown sources.
Rationale:
This setting determines whether applications can be installed from locations other than Google Play. Disabling installation from untrusted distribution channels protects against inadvertent installation of untrusted or malicious applications. Apps on Google play are vetted by Google Security Team and are mostly safe to install. You should avoid installing apps from anywhere else.
Solution
From the MobileIron console, open the Policies & Configs -> Policies view. Under the Lockdown Policy verify that Unknown Sources is disabled.