In May 2017, a Skype for Business Server 2015 Cumulative Update was released, enabling "Hybrid Modern Authentication" for Hybrid and On-Premises Skype for Business customers.
Modern Authentication allows customers to enable many modern security features, such as Azure Active Directory Conditional Access or multi-factor authentication. It also enables the Intune App Protection features for the Skype for Business iOS and Android apps.
Intune App Protection allows organizations to control Data Loss Prevention (DLP) settings for their Skype for Business users.
If you target the Skype for Business app with App Protection policies and Modern Auth is not enabled, your App Protection policies will not apply successfully.
To enable Hybrid Modern Auth, use the steps outlined in the following guide:
Once all prerequisites have been met and all steps have been completed, your organization can target their Skype for Business DLP policies and provide another layer of security for your mobile users.