In Windows Server 2016, you can check if an HTTP outbound proxy server is configured using the following methods:

Using Internet Options

Press Win + R to open the Run dialog box.
Type inetcpl.cpl and press Enter to open the Internet Options window.
Go to the "Connections" tab and click on the "LAN settings" button.
In the "Local Area Network (LAN) Settings" window, check if the "Use a proxy server for your LAN" checkbox is ticked. If it is, you can view the proxy server address and port number in the "Address" and "Port" fields.

Using the Command Prompt

Press Win + X and select "Command Prompt (Admin)" or "Windows PowerShell (Admin)" from the menu.
Type the following command and press Enter:

netsh winhttp show proxy

If an HTTP outbound proxy server is configured, you'll see the proxy settings in the output. If no proxy is set, you'll see "Direct access (no proxy server)".

Using PowerShell

Press Win + X and select "Windows PowerShell (Admin)" from the menu.

Type the following command and press Enter:

Get-ItemProperty -Path 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings' -Name ProxyEnable, ProxyServer

If an HTTP outbound proxy server is configured, you'll see the ProxyEnable value set to 1, and the ProxyServer value will display the address and port of the proxy server. If no proxy is set, ProxyEnable will be 0, and the ProxyServer value may be empty or not present.