these are the scenarios where you need IFD to be implemented for Dynamics 365 CRM.
Exposing the Microsoft Dynamics 365 website to the Internet is not supported unless claims-based authentication is used and Microsoft Dynamics 365 is configured for IFD.
Similarly, Outlook Anywhere (RPC over HTTP) is not supported as a solution to connect Dynamics 365 for Outlook to an on-premises deployment of Microsoft Dynamics 365 Server over the Internet. The on-premises deployment of Microsoft Dynamics 365 Server must be configured for IFD.
In order for Microsoft Dynamics 365 for tablets to successfully connect to a new deployment of Microsoft Dynamics 365 Server, you must run a Repair of Microsoft Dynamics 365 Server on the server running IIS where the Web Application Server role is installed after the Internet-Facing Deployment Configuration Wizard is successfully completed.
Regards,
Sudhanshu
