Emails have become a regular part of our daily life as it is the easiest and most professional mean of communication for personal, academic, and business purposes. But, do you know the entity that is responsible for transferring your emails from one place to another as soon as you click 'send'? An email protocol known as Simple Mail Transfer Protocol (SMTP) is the key player behind your email transmissions. But, what is the concept of SMTP and how does it work? To acquire these answers, let us dive deeper into the details of this article.

What is SMTP?

Simple mail transfer protocol, aka SMTP, is a standard email protocol that enables the user to send email messages to another person using the Internet. This protocol consists of a certain set of instructions/commands which allows quick email exchange between two or multiple people simultaneously.

SMTP Server

An SMTP server is an application that primarily manages the sending, receiving, and/or relaying of an email between the sender and the receiver. It is like a post office that receives your letter, performs on it the necessary processing, then posts it to the post office located nearest to your destination in another city, which then delivers it to your assigned final destination. The email transmission over SMTP passes through different communication endpoints known as SMTP ports that forward the emails toward the SMTP servers located nearest to the destination.

How does SMTP work?

When a user clicks on 'send', an SMTP connection to the server is initiated by the email client through Transmission Control Protocol. After this, the SMTP client uses commands to give necessary transmission instructions to the server including the sender's email address, the recipient's email address, and the email content. Then, the Mail Transfer Agent (MTA) checks whether the provided email addresses belong to the same email domain, or different. If the same, then the email is sent right away. If different, then the server first identifies the domain using Domain Name System (DNS) and then sends it to the respective server.

Difference between SMTP and other Protocols: POP and IMAP

Along with SMTP, POP (Post Office Protocol) and IMAP (Internet Message Access Protocol) are two other email protocols used in the email transmission process but SMTP is the most popular protocol among them because:

  • It can send emails to unknown email servers whereas POP and IMAP can only receive emails from verified servers belonging to their own network.

  • SMTP can send emails while POP can only receive emails and IMAP can only retrieve messages and handle incoming calls as they both are message access protocols.

SMTP Server Options: Run your Own or use a Third-Party Email


There are two options for using an SMTP server: Run your own SMTP server or use a third-party service. Both options have their own pros and cons, as discussed below:

Run your own:

  • A dedicated SMTP server allows you to send unlimited emails as per your business requirements on daily basis.
  • It keeps your company's email list information confidential.
  • But, it requires a skilled team to manage the server's operations, ensure its consistent availability, and secure it from unauthorized users.

Third-Party Service:

  • You do not need to care about the maintenance of the server as the third-party will be responsible for all the technical issues.
  • You do not need to invest your time and money in hiring a skilled team for operating the server.
  • The disadvantage is that if you are completely dependent on another company, if they are not expert and supportive enough, your business may face serious challenges.

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