The mobile app communicates with a so called Mobile Component. This mobile component should be installed in the DMZ of your network. The mobile component should have access to the SSP database. Firewall updates may be required to enable this access. From any internet connection in the world the mobile component should be accessible.
As an alternative your phone may support a VPN connection into your corporate network. With such a connection enabled the Mobile Component can be placed in another location than the DMZ. Please note that in such a situation, the app will only work in case the VPN connection is enabled.
A third option is to use Mobile Iron. The SMTX app has build-in support for Mobile Iron. Please read the manual for further information about the usage of mobile iron.