Help with outlook feature using Registry or GPO

Hello Team,

I want to disable or grayed out "Don't download pictures in encrypted or signed HTML email messages" from trust center-->Automatic download. But I am not getting any option.

I have installed latest ADMX and ADML templates  still not able to get the option to disable it. I am using outlook 2016 latest update. 

Any help would highly appreciated.

Regards,

Abdul Samad