This property specifies the Login (username) to use when
connecting to a remote server through a proxy server. As
some proxy servers require authorization for access, the
ProxyLogin and ProxyPassword
properties enable the user to specify their logon name and
password on the proxy server.
Among all the supported proxies, only Socks
4, Socks 5,
ProxyWebStandard and ProxyWEBNtlmAuth protocols
support authorization of this type.