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 a logon name and
password on the proxy server.
Of all the supported proxies, only Socks
4, Socks 5, ProxyWEBStandard and
ProxyWEBNtlmAuth protocols
support authorization of this type.