Email servers explained: SMTP, IMAP, POP3 & how email really works

Every time you hit “send” on an email, a complex chain of events begins behind the scenes. What feels instant to you is actually powered by an email server—the backbone of digital communication. These servers work around the clock, making sure your messages are delivered to the right inbox, and that you can receive new emails seamlessly.

Understanding how an email server works isn’t just for IT experts. Whether you’re creating a new business email address, migrating accounts, or simply curious about the process, knowing the basics will help you troubleshoot issues, configure your email client, and keep your communication secure.

In this guide, we’ll break down what an email server is, the different protocols it uses—like SMTP, IMAP, and POP3—and how everything works together to ensure your emails reach their destination.

What is an email server?

An email server (also called a mail server) is a specialized computer system responsible for sending, receiving, and storing email messages. Think of it as a digital post office: when you write and send an email, the server makes sure it’s delivered safely to the right recipient. When you receive an email, the server stores it until you open it in your email client (like Outlook, Apple Mail, or Thunderbird) or through webmail services such as Gmail or one.com Webmail.

An email server communicates with your devices and your webmail 

Another key task of an email server is to communicate with your devices and webmail so you can access your messages wherever you are. Once the server receives a new email, it delivers it to your email client or webmail interface, where you can read, reply, forward, or organize it into folders.

Any action you take—like deleting a message on your phone or moving it to a folder on your computer—is synced back to the server. This way, your inbox looks the same across all your devices.

This process relies on standard communication protocols such as IMAP (for receiving emails) and SMTP (for sending them). Thanks to these protocols, email servers keep your professional and personal communication consistent, whether you’re working on your laptop at the office or checking your inbox from a smartphone on the go.

What is IMAP?

IMAP (Internet Message Access Protocol) is the standard email protocol that allows you to access and manage your messages directly on the server, instead of downloading them to a single device. This means that every action you take—reading, deleting, or moving an email—is instantly synchronized across your phone, computer, or tablet.

For example, if you check your inbox on your smartphone during your commute, the same changes will be reflected when you later log in from your laptop at home. This makes IMAP the preferred choice if you use multiple devices to stay on top of your emails.

To set up IMAP, you usually need to enter your email provider’s IMAP server address, port number (commonly 993), and your login credentials. If you’re unsure of the exact details, you can always check your provider’s documentation or support page.

Your IMAP email server has an additional function. It lets you get invites for events that go to an online calendar, which also enables you to obtain contact information for your address book.

What is SMTP?

SMTP (Simple Mail Transfer Protocol) is the standard protocol used to send emails. While IMAP manages your incoming messages, SMTP takes care of delivering the ones you send. Think of it as the digital postman that picks up your message and ensures it reaches the right destination.

Here’s how it works: when you hit “Send” in your email client, SMTP connects your device to your mail server, authenticates your account, and forwards the message to the recipient’s server. From there, the recipient can access it through their own protocol (usually IMAP or POP3).

Most email clients handle SMTP automatically, but in some cases—such as adding a new account or setting up a business email—you may need to enter the SMTP server address, the port (commonly 587), and your login details.

Without SMTP, your emails wouldn’t leave your outbox. By ensuring secure and reliable delivery, this protocol plays a crucial role in keeping digital communication flowing smoothly.

What are MX and DNS?

If you are going to activate an email for your company but your domain is not in the same location as your mail server, you may need to change the Domain Name System (DNS) settings for your domain’s mail exchange (MX) record. MX is an entry in your DNS settings that tells you where your mail server is located. With the right MX setting, you can direct incoming mail to the right server.

If you have both your domain and your webmail at one.com, you do not need to change your MX settings.

How does an email server work? A step by step look

Sending an email might feel instant, but behind the scenes your message goes through several steps before reaching the recipient. Here’s the journey simplified:

1. You hit “send.”

You’ve written your message and included your recipient’s address. Now, you click to send it to its destination, triggering the rest of this chain of events, which starts with your electronic mail’s first stop: the SMTP.

2. The email arrives at the SMTP.

Your email first goes to the SMTP server, which works like a digital post office. It checks the domain in the recipient’s address (for example, @company.com) and looks up where that domain’s mail server is located.

3. An IMAP server receives your email.

Once the servers use the electronic mail domain to determine the correct address, the IMAP receives it with the information needed to send it to the right person. With this data, the IMAP connects with the recipient’s account and sends the text to its recipient.

4. Your message reaches its destination.

Here, the IMAP server provides another function. It enables the email recipient to read the text. The recipient can then interact with the message, whether to answer, forward, or delete it. If they choose to answer the electronic mail, their response will go through these same stages, and the cycle begins anew.

SMTP and IMAP may also encrypt and decrypt your information, depending on the setup used. After all, a proper email security protocol goes beyond a spam and virus filter.

Pro-tip: You can also consider using a POP3 server. POP stands for “Post Office Protocol” and it deletes your electronic mail after it’s downloaded from a computer, further bolstering security. You can usually select POP3 instead of IMAP for your mail.

Understanding the email process

Despite how widespread email has already become, most users are unaware of the complex process that lies behind it. While it looks instant, the mail server at the centre must carefully follow a series of steps ensure your mail is both sent and received correctly.

Here’s a quick overview of what we’ve covered:

What is an email server? Email servers are the computer networks equipped with protocols that an electronic mail goes through before reaching its destination.

What is a SMTP server for email? It’s the standard protocol for outgoing mail, which lets the email client determine the right destination for an email.

What is an IMAP email server? It’s the protocol that lets you receive emails. You can use POP3 as an alternative protocol.