OMA-URI: ./Device/Vendor/MSFT/Policy/Config/Firefox~Policy~firefox/Proxy Value (string): <enabled/> <data id="ProxyLocked" value="true | false"/> <data id="ConnectionType" value="none | system | manual | autoDetect | autoConfig"/> <data id="HTTPProxy" value="https://httpproxy.example.com"/> <data id="UseHTTPProxyForAllProtocols" value="true | false"/> <data id="SSLProxy" value="https://sslproxy.example.com"/> <data id="FTPProxy" value="https://ftpproxy.example.com"/> <data id="SOCKSProxy" value="https://socksproxy.example.com"/> <data id="SOCKSVersion" value="4 | 5"/> <data id="AutoConfigURL" value="URL_TO_AUTOCONFIG"/> <data id="Passthrough" value="<local>"/> <data id="AutoLogin" value="true | false"/> <data id="UseProxyForDNS" value="true | false"/> This has mixure of String and Integer , when we configure as string and use one from the above or leaving blank or setting only string , it failed the policy with error - -2016281112