What Is SMTP?

Millions of individuals use email communication on daily basis but most of them are unaware of how emails are sent from one place to the other. A number of protocols are used to transmit an email. These protocols work together to sure an email is sent effectively. The Simple Mail Transfer Protocol is the most significant of them (SMTP) let us discuss this primary email transfer protocol SMTP in this article.

The SMTP protocol establishes guidelines for email transmission over one or more networks. It focuses mostly on sending emails; SMTP is one of several protocols used for receiving emails.

In addition to SMTP some other protocols such as IMAP and POP are also used in email transmission. POP and IMAP are used to access the contents of a mailbox on an email server, and SMTP is used to connect to an email server for outgoing messages.

History Of SMTP

Email was first used in history during the ARPANET project in the 1960s. The primary goal at that time was to link research sites across the US. For this reason, the first email is credited to the ARPANET.

Prior to then, businesses had been using an exclusive communication protocol that limits communication between computers of the identical class linked to the same centralized system.

Email communication is now possible as a result of several attempts and efforts. Due to this, we are now using cutting-edge technology like Ethernet and 4G or 5G internet.

No matter the sort of technology we're using or whether we're using a 5G network or an Ethernet connection to access the internet, we now consider it normal that we can communicate on the internet.

Regardless of technology or connection topology, computers could communicate due to the TCP/IP set of protocols which marked a significant advancement in network communication. TCP/IP enables the use of alternative protocols for a different types of applications. Due to this, SMTP may implement only the particulars of email transfer and avoid low-level intricate specifications.

Working Of SMTP

Client Server

When you are an end user you can connect with the mailing server. For an instance, if you use Yahoo, your mail server is the Yahoo interface, which you may access using a search engine or a mobile application. You can transmit an email over SMTP by using a program like Mail. app since the server that supports Yahoo mail implements the protocol.

Email Server

Your email client transmits the email to your mail server, which might be a server run by Google or any other email service. This server receives the email just after you transmit it. After receiving the email the server executes a DNS query which converts the recipient's domain portion after the '@' in user@domain.extension into an MX record.


An SMTP session is formed between the sender and the receiver once the servers of the sender and recipient have been determined. In order for the server and client to authenticate and concur on the objective for the connection. for this authentication, the handshake is started by the caller's server issuing the recipient's server a welcoming HELO or EHLO message.

Mail Transaction

After a successful connection, the SMTP client may start delivering the email to the receiver. This transaction comprises the transfer of several instructions, including MAIL FROM to specify the sender, so that the email process can be completed. Finally, upon delivering the complete email, the server then sends the QUIT command to terminate the connection.


SMTP is the backbone of almost all email systems. The actual receiver of an email is not always the SMTP server that receives it from a client. It's possible for a server to receive inbound emails only to forward them to another server. In this instance, the server acts as an SMTP client while sending emails to other clients.