|  | 8.6 | TCP/IP Fundamentals
| 8.6.5 | The purpose and function of internet domain name server hierarchies (how email arrives in another country)
The Internet Domain Name Server consists of a root and subdomain. The root represents the upper-indexed pointers to other DNS servers. For example, when a user, user@cisco.com tries to send an email to an international location, a student at the University of Cambridge in England, student@cam.au.uk, the DNS server first contacts the subdomain server, which is cisco.com. The DNS server sends the email to the subdomain. Once the subdomain, cisco.com, has been contacted, the email is then sent to the root, .com. The root will pass it along the other roots, to .uk, which stands for United Kingdom. The .uk root passes the email message down its hierarchy to its subdomain .au and then to .cam. Once .cam receives the data, the email message sits on the POP3 server until the mail is requested.