To configure WebClient to use a specific DNS server or rely on the system's resolver, you'll need to customize the underlying HttpClient's resolver. If you want to stick with the system DNS, use DefaultAddressResolverGroup.INSTANCE, which follows your OS-level settings. To set a custom DNS server (like 8.8.8.8), create a DnsAddressResolverGroup using a DnsNameResolverBuilder and a SingletonDnsServerAddressStreamProvider.

If you're working with an HTTP proxy, make sure it's properly set up in HttpClient and supports HTTPS tunneling through the CONNECT method. In more locked-down environments, it's a good idea to combine proxy settings with the system resolver and enable wiretap logging for better reliability and easier debugging.