How Email Works: A Simplified Technical Overview

For most people, email is a part of everyday life—something we take for granted in our daily routine.

From the user’s perspective, sending and receiving an email might seem like a straightforward process, but behind the scenes, there’s a complex network of servers and protocols ensuring that messages reach their destination quickly and efficiently.

History of Email

Email was invented before the internet, as we know it today, even existed.

In the 1960s, within the ARPANET communications network—developed by the United States Department of Defense—a system for transferring emails was created.

Ray Tomlinson, the man credited with this breakthrough, introduced the "@" symbol to separate the username from the server.

This format, user@server, made it possible to send emails to specific individuals on specific machines, much like how postal addresses differentiate between the recipient and their location.

The Email Sending Process

In many ways, sending an email can be compared to sending a physical letter, though it’s much faster and more efficient. Below is a breakdown of the technical process that occurs when we send an email.

Sending Stages

  1. Writing and sending:

    • After composing the email and clicking "send," the message is transferred to the Mail Transfer Agent (MTA) using the Simple Mail Transfer Protocol (SMTP).

  2. DNS Query:

    • The SMTP server queries the Domain Name System (DNS) to find the recipient’s address. This is done via a Mail Exchanger (MX) record, which identifies the mail server for the corresponding domain.

  3. Server-to-server transfer:

    • Once the correct address is found, the SMTP server sends the email to the recipient’s server, where it will be stored until the recipient downloads or reads it.

This process resembles that of the postal system, where a package is sent from one post office to another until it reaches its final destination.

Email Receiving Protocol

The process of receiving emails is equally structured, with servers and protocols working behind the scenes to ensure that emails arrive securely at their destination.

Receiving Process

  1. Sender verification:

    • The recipient’s server locates the sender’s server, and before accepting the message, requests information about who sent the email.

  2. Sender authentication:

    • The sending server provides the sender’s details by checking the email header. Once the receiving server verifies that the message comes from a legitimate source (i.e., not spam or malicious), it accepts the email.

  3. Message transfer:

    • Once satisfied with the sender’s authenticity, the receiving server requests the email content and stores it in the recipient’s server, ready to be read.

  4. Receipt notification:

    • After the transfer is complete, the receiving server sends an acknowledgment to the sending server, confirming that the email has arrived at its destination.

Protocols for Receiving Emails

After the email has been received and stored on the recipient’s server, there are two primary protocols for accessing the messages:

  1. POP (Post Office Protocol):

    • This protocol downloads the emails to the user’s device and removes the copy from the server. It’s useful if you only access your email from one device.

  2. IMAP (Internet Message Access Protocol):

    • IMAP keeps a copy of the emails on the server, allowing synchronization across multiple devices. For instance, if you read an email on your phone, it will also appear as "read" on your computer.

Structure of an Email

An email consists of three main parts:

  1. Header:

    • This includes the sender’s information, the recipient, the date, and the subject of the email.

  2. Body:

    • This is the main message content, which could include text, images, or file attachments.

  3. Electronic envelope:

    • This is the technical information that users don’t see but is essential for ensuring the message reaches its intended destination.

Emails, despite appearing simple to the end-user, involve a series of technical steps that ensure they are delivered efficiently and securely.

From verifying senders to storing messages, every stage is carefully structured to optimize digital communication in our increasingly interconnected world.