SMTP Service – The Mailman Behind The Scene

SMTP Service (Simple Mail Transfer Protocol) is one of the protocols which allow you to send, relay, or forward emails.

Email is one of the most used network tools. It has emerged as the primary means of communication worldwide within only a decade or so. We use it everywhere, for communicating with our near and dear ones, for the subscription of media, and for exchanging information with business clients and partners. We are so much into using emails in every aspect of our lives that it is challenging to imagine the modern world without it.

But have you ever thought about how email works? How does a message find its way into the inbox of the intended recipient out of the millions of users? What happens behind the scene when we hit “Send”? Below, we are going to tell you about the protocol that makes the sending of emails possible – the Simple Mail Transfer Protocol or SMTP. The information will help you learn to employ effective techniques and services for all your email-related campaigns.


SMTP Service

Quick Overview Of SMTP Service & SMTP Relay Service

First of all, an SMTP Service is a push protocol that enables sending of emails between servers. An SMTP relay service is that – usually a third-party application – which transfers email messages between different hosts and domains.

While SMTP is the protocol for sending or relaying the emails, it does not take care of retrieving the emails from the server or receiving them in the recipient’s inbox. To extract the email, we need the POP or IMAP protocol. Hence, the whole process of sending and receiving the email is completed by pairing both SMTP and IMAP protocols – one sends, and the other receives.

A user who wants to send an email has first to establish a Transmission Control Protocol (TCP) connection, which is the communication protocol for sending data packets from device to device over the internet. The user then uses the SMTP services, like Google SMTP Server, to send the email to another network. On listening to any TCP connection, the SMTP service initiates the process of establishing a connection with that port (25). Once the TCP connection is established correctly, the email client immediately sends the email. It is not always necessary to use Port 25; some groups have developed other TCP ports, like 587, to improve the SMTP relay service and to reduce the problem of spamming. Gmail uses its secured TCP port, i.e., Port 465.


Email Working Process

The sending of an email has a three-step working process, which includes:

  • In the first step, the mail server uses SMTP to send an email by an email client to the email server. We can utilize any email client like Gmail, Outlook, etc. for this purpose.
  • Secondly, the email is sent to the receiving email server from the sending email server by using an SMTP relay service.
  • In the third step, the server of the recipient downloads the received email with the help of an email client using IMAP (Internet Message Access Protocol) or POP (Post Office Protocol) and the email is placed in the inbox of the recipient.

If we study the process in detail, we can say that SMTP simplifies the process of sending emails between different email servers by using a set of codes. The outbound SMTP breaks the message inside the email into different categories so that the receiving server can understand it quickly. When the sending server transfers the email to the receiving server, the message is converted into strings of texts which are then divided using the code words, and the purpose of various sections of the message is identified. The SMTP provides the codes, and the design of the email server software is such that they can understand the meaning of these codes. The receiving protocols then convert them into meaningful messages again, and that is what the recipient sees and reads.

When an email moves to the destination server, there are chances that it has to pass through several other computers or Mail Transfer Agents (MTAs). In the process of moving, some parts of the email are also briefly stored before it is transferred to the next MTA or computer. In simple words, we can understand it as a letter which has to move through various hands and post-offices before it reaches the correct mailbox.


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SMTP Is Very Simple

The thing about an SMTP service is that it can handle and transfer only the text part of the emails. It cannot code graphic designs, stylish fonts, or attachments, etc. To cover this shortfall of SMTP, developers create the Multiple Internet Mail Extension (MIME). The work of MIME is to encode that part of the email which is in non-text form into plain text. Once it encodes the non-text content, the SMTP can read the material and is, therefore, able to transfer the email quickly.


SMTP Models

SMTP can be categorized into two models:

  • End To End Model: This model is used to send emails to different organizations.
  • Store And Forward Model: This model is used to send emails within an organization.


Basic Requirements For Configuration in SMTP Service Windows

In the SMTP service windows, we have to do some configurations for SMTP, and the basic things required for such settings are as follows:

  • Host Address: The first and foremost requirement while configuring the SMTP server is the address of the host server. The address is required to authenticate the user to send the email.
  • The number of the Port: The port number is an essential requirement while configuring the SMTP service. It is so because this number is the only way to determine a particular process in which to transmit the message from the server of the sender.
  • Encrypting the Email: Encryption is needed to prevent any unauthorized or unwanted user to read or get access to the sent email. Through this, the email remains safe as only the recipient who is intended to read the message can get access to the content of the email.


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Free SMTP Server List

The user can use free or paid SMTP servers according to his/her needs. Some providers offer free, reliable SMTP services. Let’s take a look at some of the best:

  • SendinBlue
  • Mailjet
  • SendGrid
  • AmazonSES


Google SMTP Server

If you use Gmail as an email client, you are already using server Google SMTP Server – for sending your emails. As we’ve said above, you need an SMTP service to be able to send emails, and this particular service is what enables you to do so with Gmail. You can also use the free SMTP service with desktop mail applications like Outlook, Thunderbird, etc.


Drawbacks Of SMTP Service

A majority of the mail transfer services uses the SMTP service. But, one of the drawbacks of SMTP is that it is only a sending protocol. POP and IMAP are the other protocols which you need to use in connection with SMTP to receive the emails. This means that SMTP alone is unable to complete the process of transferring the email.

Another problem with SMTP servers is that spammers use free servers to generate several junk or malicious emails to exploit the users. In addition to this, cybercriminals can even use fake email addresses in the “From” column of the SMTP.

With time, SMTP service is improving. Technology advancement has made it possible to make the SMTP servers more secure and protected. Various measures have been taken against the spammers to provide safety to the users. So, you can continue to employ the useful SMTP service to enable you to communicate with your family and friends, business partners, clients, etc. without fear.

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