At one point during the evolution of the Internet is was necessary to know which constituent network a site belonged to, and to use that network's
naming scheme as part of its Internet name. For example, a network of Unix machines known as UUNET identified a site by the path a message traversed in reaching the site. A command of the form
% mail drizzle!fog!mist!fred
meant ``send a message from this machine to host drizzle, have it forward the message to fog, and have fog send it to the user named fred on mist.'' When drizzle was connected to the Internet, Fred's colleagues at other Internet sites could send him mail via the address `` firstname.lastname@example.org''. Now, however, you would probably reach Fred simply by using the domain name of his organization, i.e.
% mail email@example.comYou will still see host names and user names that contain network- specific fields, but they are becoming increasingly rare.