The solution !
Key Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Options\Mail
Key Outlook 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\Mail
Value type: REG_DWORD
Value name; Send Pictures With Document
Value: 1
Note: The value name contains spaces and capital letters; you must include these as well.