SMTP Simple Mail Transfer Protocol: What it is, how it works and how to use it correctly

Opening or sending an email is a simple task for most of us. However, you should know that for this to happen there is a server – client structure, where there is a user who is the one who sends the message and a server who is the one who processes and receives it.

For this to happen, the data that make up the email must be transferred, for which the SMTP protocol is used, which means “Simple Mail Transfer Protocol”, where certain rules are executed so that the email can be sent. It goes without saying that without this protocol this could not happen.

The technique that exists today has a high quality in terms of sending and customizing emails, as several of us use it frequently.

What is the SMTP Protocol and what is it used for in computer networks?

SMTP is an email transmission system that, like TCP/IP, is integrated with the Internet protocols. It is used with the intention that users can receive and send emails.

It is usually used with POP3, or with the Internet message entry system called “IMAP”, which is used to save the messages inside the server’s mailbox, and then be able to download them constantly to the destination user’s server.

The referred protocol are the standards used with the intention of authorizing the transmission of information within a computer network, being that the SMTP itself is an Internet system.

There are cases where SMTP is only used for sending emails, as there are some limitations at the technical level to be able to accept them. This makes it necessary to use other types of Internet systems, such as the Internet Message Access Protocol (IMAP) or the Post Office Protocol (POP), for reception.

The above means that when an email is sent, the IP address of a spammer is shared, which means that a circumstance occurs where the prestige of sending is damaged, which predominates in the proper delivery of clean emails.

When the user sends an email through the SMTP protocol, what happens is that the user of the email, such as: Mozilla Thunderbird or Outlook Express sends a message through a server via SMTP. This server transports the message to the “Mail Transfer Agent (MTA)”, through the “Domain Name System (DNS)” in order to obtain the “MX record”.

When the message is accepted, it goes to a “Mail Delivery Agent (MDA)”, which may need the SMTP execution again in order to make the delivery to the email server. Therefore, through “IMAP” the recipient obtains or retrieves the message in his email account.

Which is the SMTP server of the most important email services and how to use them for free?

We will now explain how the SMTP protocol works with the most common email services used by users:

Google Gmail

It is a completely free server that is used for those companies or people who do not handle a large volume of emails. It is an excellent option when you need to use Gmail and send chain emails.

Gmail itself has a very large space, so it is reliable when you want to use their services online. But it has certain limits, since it only allows one hundred emails to be sent in an estimated time of 24 hours when you want to play them using the SMTP protocol. This would result in 3,000 free emails for a period of 1 month.

The above amount may be sufficient when your business is small, since in case you want to increase the fee you will have to pay the amount they charge for the payment service. The information you submit is available anywhere you require it.

Microsoft Outlook/Hotmail

This is one of the most used email services by Windows users, since it comes pre-installed in the systems and helps people to communicate via messages with other people through the SMTP system, you can also access emails through POP3 or IMAP protocols.

We must say that it is very complete, since you manage to enjoy antispam filters, shared mailbox, organizer of agendas, organization of tasks, filter of contacts, calendar, to look for messages and to be able to personalize it to your way. Also, it is programmed and used to work with the mail protocols you prefer.


The SMTP servers in Yahoo are used for outgoing emails, which means that for your incoming emails other types of protocols such as POP or IMAP are also used. You usually get these protocols in the settings tab where you add the Yahoo account.

You can get these types of Yahoo protocol on Google whenever you want. They are also used with much more protection through an additional security layer that is placed in your Yahoo account.

That is why when another user wants to access your email it is blocked by this server in case your security is not standard. It is important that you know that it is not good that you activate the option “Less secure applications”, because this can be a danger for your account and for your personal information.

It is recommended that before setting up your email you check very well what each option is for, to avoid any kind of inconvenience with your account.

What are the main features of the SMTP network protocol?

Over the years e-mail has been a means of communication for Internet users, one of the most widely used protocols being SMTP which stands for “Simple Mail Transfer Protocol”.

Among its essential characteristics we can indicate the following:

  • It has text commands that are very easy to use.
  • It is a network protocol used for electronic messages.
  • It helps users to stay connected through a server, as messages are sent and received.
  • It has lines of text where the instructions of this system are specified.
  • They provide the option of being able to exchange e-mail messages via “TCP/IP hosts”.
  • It is made up of 3 protocols that are standard and that are applied to mail, among which are: MAIL, DATA and RCPT
  • It can be configured in conjunction with other protocols such as: POP3 or IMAP
  • Sometimes SMTP is only used for outgoing mail, while POP3 or IMAP is used for incoming mail.
  • With it there is the option of being able to synchronize a Smarthost server.

SMTP vs POP3 Which is better and how do they differ?

Both protocols are used to manage e-mails on the Internet, but it must be made clear that each plays a different role in the dynamics of sending and receiving e-mails.

Among the most outstanding differences we have the following:

  •  SMTP is used to send messages, while POP3 is used to receive them.
  • With SMTP there is the sending server; and with POP3 there is the receiving server.
  • The SMTP sends the email from the sender’s computer to the receiver’s mailbox; while with the POP3 you can retrieve and organize the emails inside the receiver’s mailbox to the destination computer.

SMTP vs. IMAP Which is better and what makes each one different?

Usually, emails are stored inside the server of the incoming email that has not been opened by the user.

However, when the user sends a message, it is uploaded to the outgoing mail server via the SMTP protocol and is immediately directed to the receiver’s inbox.

Unlike the IMAP server, where the message is located on the receiving device without being downloaded from the server, that is, when an email has been opened on a device, when entering from another one it comes out as read, and at the moment the user makes the request it is necessary for him to connect permanently to the Internet so that he can enter the email and see the message.

Because there is no need to download the messages it is much easier to read them. Also here you can sort the folders, so that any user can see them. It should be noted that when a user makes a change in the server, other users can see it. It is important to program the time that the user has access to new messages, something that can also be done manually.

This post is also available in: Português (Portuguese (Brazil))

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