SMTP email or Simple Mail Transfer Protocol is an internet application for delivering electronic mail transmission across networks related to Internet Protocol. In the present world, emailing has emerged as a necessity as well as a faster mode of communication. Due to its worldwide popularity, emailing is considered an integral part of the corporate world and various business organizations. However, there are many people who are hardly familiar with the internal processing of emailing. After you click on the ‘send’ button in your email program, you remain generally unaware as to what happens next apart from the fact that your mail has been sent. So, in this entire process of emailing, SMTP email plays a big role.

As soon as you sent an email, your email program instantly becomes an SMTP client. Next, it is connected to networking points of your email server known as Port 25. The SMTP email command usually consists of four characters. One of them is EHLO that lets the server promote supplementary features such as the capacity to deliver messages or providing status information. SMTP email also specializes in outgoing mail transport.

The mail transfer agents and the servers take the help of SMTP email for sending and receiving mail messages. On the other hand, the user-level client mail applications depend only on SMTP email to send messages to a mail server for the purpose of relaying. The client applications generally make use of the Post Office Protocol or sometimes the Internet Message Access Protocol to connect to their mail box accounts on a mail server.

While SMTP is considered to be a delivery protocol for its inability to draw messages from a remote server, Post Office Protocol and the Internet Message Access Protocol on the other hand are exclusively meant for recovering messages and supervising mail boxes. The SMTP email protocol sets off the processing of mail queue on a remote server in such a way that the requesting system can receive any sort of message. In a user’s PC when an internet connection does not work consistently and the host fails to receive messages being offline, the two most considered protocols that are used in such instances are POP and IMAP.

SMTP Transaction

There are three reply sequences of SMTP transaction: They are:

• MAIL - The MAIL command is used to ascertain the return address which is applicable only for the Bounce messages.

• RCPT - The RCPT command ascertains the receiver of the message, and it can be used several times.

• DATA - The DATA command helps to send the message text. It comprises of a message header and a message body.

Outgoing Mail SMTP Server

It's important for an email client to know the IP address or name of an SMTP email server required for its configuration. Its on behalf of the user that the server will carry the messages. However, the email provider services can be used by the end users being connected to the Internet. Whether the client is located within or outside the network is no more a limitation for email submission or delivery.

SMTP Service

The process of delivering and transporting email through the Internet to the destination server is considered an integral part of SMTP service. While emails are delivered and received in between servers, the POP3 recovers email right from the mail server to the user’s PC. It is very important to choose a physical location for the service directory which too forms part of an SMTP service.