Telnet is a networking protocol to access a machine remotely and transport files between two machines. EMAIL basically works on a session based telnet. The user accesses mails from an email client. The messages and other details are transported from the server to the station where the user accesses his messages. The local PC from where he accesses his messages are termed as email client.
So when the user logs on to his e-mail the messages reside in a folder in encrypted format on the email server. Public email such as hotmail have a common server from which users access emails. Due to the large volume there may be multiple machines used for storing messages. There is infact only one email program that is rendered on the server. The user sees a copy of the program on his client.
All mail transfers work on the foundation classes of Telnet. There are several mail protocols such as SMTP ( Simple Mail Transfer Protocol), POP ( Post Office protocol) and MAPI. In fact Internet mail such as hotmail can be received and sent from the desktop as well using e-mail clients such as microsoft outlook and outlook express. In fact these service providers prohibit reconfiuring hotmail/yahoo etc., on your desktop clients.
A desktop client such as Microsoft outlook or Outlook express serve the purpose of sending and receiving emails. An email client can be constructed using application software such as Visual Basic. Mobile phones send and receive emails using GPRS services.
Normally one has to develop a stratergy to archive old messages. Otherwise the email account becomes unmanageable. Either the old mails can be downloaded to a folder on your hard disk or deleted periodically.