What is SMTP (Simple Mail Transfer Protocol)?

SMTP is an application layer protocol and is a text-based technology used for exchanging email messages between computers or other devices. This protocol, which started to be developed in the early 1980s, is defined in RFC 2821 and is an official Internet standard.

What is SMTP Protocol?

What is SMTP Protocol and How Does It Work?

Today, the most popular service for sending an email is SMTP. The Mail Protocol is used to send email from one server to another server over the Internet.

In short, it is used to send electronic Mail (Email) between two different hosts and works at the application layer.

SMTP History

As more computers began to connect with others, including the ARPANET network initially created by the US government, standards were developed that allow users to use different systems to use email with each other.

SMTP was one of these standards developed in the 1970s. Work continued in the 1970s until ARPANET transformed this into the modern Internet around 1980.

Jon Postel later proposed a mail transfer protocol that began removing trust from the Mail on FTP in 1980.

It was published as RFC 821 by Jonathan Postel in August 1982. Since this standard was developed simultaneously with USENET, it has been accepted as one of many communication networks with some similarities.

Later, it was widely used in the mid-1980s. At that time, UUCP (Unix to Unix Copy) was used as a complement to Mail, which was better suited for email transfers between machines that were intermittently connected.

How Simple Mail Transfer Protocol Works?

The SMTP protocol also uses port 25 when making a TCP connection. The client uses this port (25) to send Mail to its recipient. When the TCP connection is successful, both Request and Response are initiated. In this process, the sender and recipient’s email addresses are determined. Then, when the server accepts mailing addresses, the client sends the Mail to the recipient.

An Email must have a message header and a message body. The user can receive Email messages using the Post Office Protocol (POP) and Internet Message Access Protocol (IMAP).

The Mailbox program must be installed on the user’s computer to send and receive emails. The user with a mailbox program needs to configure POP or IMAP in order to send an email.

Users may not know they are using this protocol when sending emails. Nowadays, with the development of technology, sending and receiving emails has become very easy. Internet access users can easily send and receive Emails using Web-based email services.

Examples of web-based email services are Microsoft’s Outlook Service and Google’s Gmail services.

In short, a computer user can install an email program on your computer and control all Email traffic from one location.

How Does SMTP Work in a Corporate Network?

Email services are probably one of the most used services in corporate networks. The most common protocol that underlies the use of email in such internal networks is SMTP.

As with many Internet and network applications, SMTP uses a client/server architecture. When a person wants to compose a message, they use a mail user agent, client software running on a computer, to create an email fragment.

This user agent can be any of the email programs that can run on different systems on computers.

After the message is complete, the agent sends it to a program running on a server called the MTA (Mail Transfer Agent) that examines the address of the message recipient.

If the recipient of the message is on the local network, the MTA sends the message to another server program called MDA (Mail Delivery Agent) in the internal network.

If the recipient is on the Internet or another network, the file reaches the recipient via the Internet. The MDA examines the recipient’s address and sends the Mail to the appropriate person’s inbox.

Some mail systems use another email protocol called POP in conjunction with SMTP. With the POP protocol, email is not delivered directly to your computer. Instead, the Mail is delivered to a mailbox on the server.

To retrieve the Mail, someone accesses the server using a password and username and can download the message to their computer via a mail agent.

In this case, the recipient of the Mail can now use a mail user agent to read, archive, and reply to the message.

SMTP can only handle the transmission of ASCII text files via email. To send binary files such as spreadsheets, drawings, and word-processing documents, they must first be converted to ASCII format.

Some email software can automatically encode binary files. When a person receives an encoded file, it decodes it and can either use the binary file or access it. In addition, many email packages automatically decode encrypted files.

How to Configure Mail Settings in Windows 10

For example, in the image below, you can see the mail program built into Windows 10. With this mail program, multiple email accounts are controlled and managed.

Windows Mail Program

For example, you can see the SMTP setting of the MAIL SERVER used to send an email in the picture below. Here, you can examine that the SMTP protocol is configured in the Outgoing section.

If you want to set up Mail on your Windows 10 computer, you need to configure the Outgoing and Incoming fields in the picture below. You can obtain the information by contacting your hosting company.

When you view the image below, the info@sysnettechsolutions.com email address contains the hosting company’s records.

Mail Settings

How to Configure Email Security in Windows 10

SMTP Server security is critical. If the necessary security settings are not configured, malicious people can send fake emails on your behalf.

Generally, the hosting company provides incoming and outgoing server settings for POP3 and IMAP. If the hosting provider does not offer SMTP (25) port security, this will be a very critical situation for you.

If there is a security vulnerability for port 25, you can connect to the server via Telnet at the CMD command prompt and send emails with a few commands. If your hosting company does not block this vulnerability, it could have dire consequences for you.


In this article, we talked about what SMTP is and how it works. Finally, we looked at how to configure mail settings in Windows 10. Thanks for following us!

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