It is currently possible to set up a network environment in which all of the major network services, except for electronic mail, are authenticated using the Kerberos or Secure RPC mechanisms.
Authentication is important with electronic mail.
When mail is sent, it is important that no one can send mail under a name other than the actual author of message sent. However, this scenario does not address the problems of electronic mail. For a discussion of electronic mail, see chapter 11 and sections 9.2.4 and 10.2.4 . Client workstations access network services from the servers. Servers are administered by responsible individuals whose job is to provide network services to the client workstations.