ScreenConnect works with proxy servers. It uses the settings defined in Internet Explorer, also stored in the registry under "HKCU/Software/Microsoft/Windows/CurrentVersion/Internet Settings" ... An issue occurs when the SC guest client runs under different users such as when logged off, viewing UAC windows, etc. It'll run under Local System in these cases. So you'll need to have it pickup the right proxy settings. The best way to accomplish that now is to set the "HKLM\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\ProxySettingsPerUser" key to DWORD 0. Then re-save the settings under Internet Explorer and ScreenConnect will use those settings under any user.