Smtp Server - A Model Of Perfect Servicing

By Author: Alvar Wills
Total Articles: 5
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Simple Mail Transfer Protocol, popularly referred to as SMTP, is the de facto standard of sending emails. Electronic mail has emerged as the advanced technology backed up tool to support us with an innovative and effective mode of communication. Be it for personal purpose or professional need, an instant and efficient communication is what we desire and demand. SMTP mail servicing system was developed to meet this objective.

How does an SMTP server handle mail delivery? Well, an easy example may explain the entire scenario in a simple yet explicit fashion. Suppose there are three computers namely A, B, C in a network system. If the computer A wants to send mail to B, the message reaches the targeted destination via SMTP server. After receiving the message, it looks for the mail server to locate the domain of the recipient residing on computer B. Once it is done, a link is established with the computer B's SMTP server. The message checking by the recipient is, however, done with the help of POP3. In case both the computers want to send mails to computer C, then another SMTP mail server pops up in the scenario.
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... br /> The above procedure does not exemplify a centralized system of email delivery as the SMTP servers can directly communicate among themselves without involving any central system for the purpose of message clearing. The messages may travel through several SMTP servers to finally reach the destination. Here the destination refers to the mailbox of the recipient. While starting session with an SMTP server, the client provides it with a source route containing a list of hosts the mail is supposed to pass through. This route is referred to as forward path. In addition, a second route, referred to as traverse path, is also provided to return error messages in the event of failure in mail delivery. The decentralized system of mail delivery is very simple and straightforward. Moreover, the failure of an SMTP server does not make the entire system come to a halt.

SMTP came into being more than a decade ago. So an urgent need was strongly felt to provide additional features and functionalities, called service extension. At first, RFC 1425 was used for this purpose and tumbled after RFC 2821 and 2920. Many an SMTP server negotiates with each other to find out which extension is compatible with each of them. Service extension is basically divided into four basic categories - delivery, authentication and security, command pipelining and enhanced status code. In original RFC, every process has a name depending on its service. For example, sender SMTP is a client that builds up a two-way session with the local SMTP Server. On the other hand, receiver SMTP is assigned the task of receiving commands from the sender SMTP. So, here the unique names have been assigned depending on the direction of the information flow. In case of RFC 2821 extension, an SMTP mail server is supposed to provide service to the local clients and relay mail messages to the other SMTP mailservers provided the destination does not refer to a client on the mail server. The entire gamut is complicated but interesting, is not it?