Simple Mail Transfer Protocol (SMTP)

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 **** Simple Mail Transfer Protocol (SMTP)  ****
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SMTP stands for Simple Mail Transfer Protocol. It is a TCP/IP protocol that specifies how computers exchange electronic mail. It works with Post Office Protocol (POP).
SMTP is used to upload mail directly from the client to an intermediate host, but only computers constantly connected such as Internet Service Providers (ISP) to the Internet can use SMTP to receive mail. The ISP server then off loads the mail to the users to whom they provide the Internet service.
Windows 2000 includes as SMTP mail client so does Windows NT Resource Kit. Microsoft Exchanging Server will route your LAN mail on and off the internet.

Working of SMTP



SMTP is a simple ASCII protocol. After establishing the TCP connection, the sending machine, operating as the client, waits for the receiving machine, operating as the serve, to talk first. The server starts by sending a line of text giving its identity and telling whether or not it is prepared to receive mail. If it is not, the client releases the connection and tries again later. If the server is willing to accept e-mail, the client announces whom the email is coming from and whom it is going to. If such a recipient exists at the destination, the server gives the client the go-ahead to send the message. Then the client sends the message and the server acknowledges it.



The problems that may arise with SMTP protocol are as follows ::

* Some older version of SMTP implementations cannot handle messages exceeding 64 KB.

* If the client and the server have different timeouts, one of them may give up while the other  is still busy, unexpectedly terminating the connection.

To get around these problems, extended SMTP (ESMTP) has been defined in RFC 1425.

See Also ::
1. What is FTP ?
2. What is NFS ?
3. What is SNMP ?
4. Types of computer attacks