To connect to an HTTPS resource via an HTTPS proxy, use the WebTunneling* properties.

The HTTP proxy and the HTTPS proxy are different (though often combined).

The HTTP proxy accepts HTTP client connections, takes the URL, requests it from the remote server, and passes the resource to the client.

The HTTPS proxy accepts a generic connection -- it accepts the "HTTP CONNECT" command (just one line and not a complete HTTP header) and establishes a pass-through tunnel to the remote host. Next, the client communicates with the remote host as it needs, not necessarily using the HTTP protocol. That is, an HTTPS proxy can be used to connect to a remote server using any protocol and not just HTTP. This is why SecureBlackbox supports WebTunneling in all socket-based client transport components.