Does this occur if I am using proxy server setup in Windows 10 settings?
If yes, can I somehow prevent it from doing so.
There are several reasons for this:
The way a proxy works, is that instead of connecting to the server directly, you connect to the proxy and the proxy connects to the server. In order to do this, the proxy needs to understand the protocol you are using to connect to the server.
The particular settings you are talking about, are for web proxies, i.e. proxies that implement proxying for typical web protocols such as HTTP, HTTPS, FTP, FTPS, WS, WSS, and Gopher.
So, that should already tell you the first limitation: it only works for a limited set of protocols, i.e. for web protocols, IOW it only works for web browsing and related things, and not, for example, for Email, or Skype, or Teamspeak, or multiplayer games, or a myriad of other protocols.
Also, in order for the proxy to be used, an application has to actually, well, use the proxy. Internet Explorer and Edge, for example, they read those settings you talked about, but not every browser does. Some browsers have their own, browser-specific proxy settings.
Lastly, the protocol itself could contain the original IP address (or other identifying data) in encrypted form, and there is nothing the proxy can do about that. For example, the WhatsApp Messenger uses end-to-end encryption, so the proxy can not look inside the protocol. And the protocol is proprietary, so nobody knows what it actually sends. It is entirely possible that it might send the original IP address, or the telephone number.
So, in short:
- The use of the proxy is completely voluntary. Only applications which read those settings and want to use the proxy will use it.
- The proxy generally only works for web protocols.
- Applications may still send the IP address as part of the application protocol.