SMTP (Simple Mail Transfer Protocol), Advantages, How it Works, 5 Commands

If you want to know about simple mail transfer protocol (SMTP), then read this blog completely, you will get detailed information about Simple Mail Transfer Protocol.

As you may know that on the Internet or a LAN network, two computers use network protocols to communicate and share information.

That is, computers have a system to interact with each other. Or you can also call it some important rules for communicating.

And so on, there are different network protocols to do all the work. Such as TCP/IP protocol for network communication and FTP protocol for file transfer.

So in the same way when we send mail to someone on the internet, then there is SMTP i.e. Simple
Mail Transfer Protocol is used. So let’s understand SMTP.

What Is Simple Mail Transfer Protocol

Simple Mail Transfer Protocol is a TCP/IP-based application layer protocol of the OSI model, used for E-mail transmission.

That is, when an E-mail is sent from a user’s E-Mail Id, then the work of sending that E-mail from the Client Computer to the Mail Server is done by Simple Mail Transfer Protocol. Is also called a push protocol, and it uses a port 25.

Similarly, this protocol is also used to transfer mail from one mail server to another.

Two more mail protocols work with this protocol, POP and IMAP. The job of both the network protocols is to download the mail from the mail server to the client computer.

How Does SMTP Work


Simple Mail Transfer Protocol works on very simple functionality, which is based on end to end network.

There are two main working points of this protocol process, the first is the computer Client which is the Mail Sender, and the second is the MAIL Server which is the Mail Receiver.

All the mail settings related to SMTP are saved in the client computer of this protocol. For example, if we take Gmail, then Smtp@Gmail.Com as well as Port No 25.

Similarly, when you use Microsoft Outlook, the settings related to Mail Server are also put in it and SMTP Port 25 will be configured.

So first of all when the e-mail is sent by your computer clients, such as through Gmail or Microsoft Outlook, then that e-mail reaches directly to the server. Where the SMTP server processes the mail.

After that, if there is mail from the internal network, then it is saved on the SMTP server itself, which is synced by the client and then that mail is downloaded to the computer by IMAP or POP.

And if there is any other external address mail, then the server transfers that mail to another, that related mail server.

Advantages of SMTP

Simple Mail Transfer Protocol is an open standard protocol, any network application can use the protocol to send email from a computer client to a server.

The simple properties and well-defined rules governing the Newark Protocol make it highly reliable and predictable.

For example, the original SMTP specification was designed to send only non-Latin text, which is less useful for people who use languages ​​with accented Latin characters or non-Latin alphabets.

And because the protocol is universally adopted, there are no compatibility issues when sending messages between SMTP servers.

SMTP Commands

  • HELO
  • Size
  • Data 

The work of this command is to communicate from one mail server to another mail server. This is the process of starting the SMTP session.


This command is used to see the mail address of the sender, in which the sender’s E-mail address is entered in the From field.


It shows the recipient of the mail, in which if there is more than one recipient, then this command is repeated on every address.


It informs the server about the size of the attached email.


With this command the email transfer starts, to start which the 354 reply code is given by the server, which is the green signal to start the process.


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