Email Protocols: Learn The Difference Between IMAP, POP3, and SMTP

Aleksandra Duło, 20 June 2024


Are you a bit baffled by email protocols like IMAP, POP3, and SMTP? Have no fear – this article is here to explain it all. If you have ever wondered how emails are sent and received, understanding these protocols is key.

SMTP sends emails, while IMAP and POP3 allow you to access them. Each protocol has its own benefits, so it’s important to determine which one works best for you. The acronyms can leave even the savviest of internet users scratching their heads.

In this article, we will explain these terms and take you on a journey into the world of email protocols.

So, grab a cup of coffee, settle into a comfy chair, and prepare to unravel the mysteries of IMAP, POP3, and SMTP. Whether you’re a tech novice or a seasoned pro, we’ve got you covered!

What Is Email Protocol?

Email protocols are the unsung heroes of the digital world. They make sure that all messages, attachments, and content are transferred safely and securely between different servers and clients.

Email protocols define the format and structure of email messages, specify how they are transmitted, and outline the authentication and security measures in place. They play a crucial role in facilitating the flow of information in the vast landscape of the digital world.

The three most commonly used email protocols are IMAP, POP3, and SMTP.

Maximize your email deliverability and security with EmailLabs!

What Is SMTP?

SMTP stands for Simple Mail Transfer Protocol. It is an essential protocol for sending emails from a server to an email client (e.g. Google Mail, Microsoft Outlook, etc.). It works by finding the best route for the message and delivering it to the recipient’s email server. This protocol uses SMTP ports to make the connection between servers for efficient delivery.

SMTP servers can be categorized into two types: relays and receivers. Relays accept emails from users and route them to the intended recipients, while receivers accept emails from relays and deliver them to the recipient’s mailbox.

How does SMTP work?

SMTP is an essential system for email sending. It is responsible for ensuring that messages reach their intended recipients quickly and accurately. Let’s take a closer look at how it works.

The process begins with the SMTP handshake. This is when a client establishes a connection with the server using a TCP connection. When the server responds with code 250, the handshaking process begins. It continues until the recipient’s address is verified.

The next step is email transfer. This is triggered when the server responds with code 354 in response to the DATA command. The transfer is completed when the server receives a final dot.

Finally, the client and server say goodbye using the QUIT command and code 221, respectively. This marks the end of the process.


SMTP Ports

Currently, these are the most common SMTP ports used:

  • Port 25 used to be the go-to port for relaying messages between email servers, but it is now often blocked by cloud hosting providers and popular email clients. This is because they prioritize secure connections.
  • Port 465 was created for SMTPS encryption and authentication, but it has since become obsolete. While it is still used by some servers, it is no longer recognized as an official SMTP transmission or submission channel.
  • Port 587 is the current default SMTP port that allows secure submission of emails, and it supports TLS encryption. This port is supported by nearly all mail servers.
  • Port 2525 is not an official SMTP port, but it is widely supported by email service providers and can be used as an alternative to port 587 if needed.


A Complete Overview of SMTP Port 25, Port 465, and Port 587: How To Choose the Right SMTP Port

What is IMAP?

IMAP (Internet Message Access Protocol) is a popular protocol for receiving emails from a remote server. IMAP protocol stores emails on the server even after they are delivered. This means that you can access them from multiple locations at the same time.

IMAP is a great way to manage your inbox efficiently. You don’t have to download the whole email until you open it. This saves time and bandwidth that would otherwise be used to download an entire message.

IMAP is a secure protocol that uses encryption to protect your emails and data, ensuring privacy and security. It operates on port 143 and supports SSL/TLS encryption.

IMAP also has the ability to create folders and subfolders for better organization.

How Does IMAP Work

When using IMAP, the client connects to the server to check for new messages and saves them in the cache as temporary files. When the client is connected, only the date, sender, and subject of the emails are downloaded from the server. The actual content of the email is only downloaded when the user opens it.

This feature allows users to quickly skim through emails without wasting time and data download. IMAP keeps the emails on the server, meaning that any changes made via one device will be reflected on all other devices in real-time.

SMTP is used for sending outgoing emails. IMAP and SMTP can work in tandem to ensure a smooth email experience for the user.


Advantages and Disadvantages of IMAP

IMAP offers convenience and freedom but also comes with some downsides.

IMAP, as an email protocol, allows you to access your emails from multiple devices simultaneously and supports keyboard-based email searching. Plus, your emails are stored on the server, meaning they are unaffected by local machine failures.

However, there are a few drawbacks to using IMAP. Accessing emails is slightly slower than with POP3 due to the synchronization of all folders during send or receive. An active internet connection is also required for email functionality. If you use your emails frequently, you may need to purchase a larger mailbox storage space, which can get costly.

What Is POP3?

POP3, short for Post Office Protocol 3, is a popular email protocol that transfers emails from a server to a client device. POP3 downloads email from the server, allowing users to read their emails offline without needing an internet connection.

The main benefit of POP3 is its user-friendliness. It is simple to set up and use, making it a popular choice for both individuals and businesses. POP3 uses port 110, and SSL/TLS encryption is optional.

POP3 is a great choice for those who don’t need to sync their emails across multiple devices. Its ability to transfer emails offline and easy setup make it a widely used protocol.

How Does POP3 Work?

POP3 is a protocol used for email communication. It allows users to access their emails offline and manage their storage space on the server efficiently.

To use POP3, the email client establishes a connection with the server. During this process, the user must provide authentication credentials (username and password) to gain access. After authenticating, the client issues text-based commands to retrieve emails stored on the server.

The main commands are:

  • USER – specifies the username for authentication with POP3 server
  • PASS – provides password for authentication with POP3 server
  • RETR – downloads an individual email message based on its unique number
  • LIST – retrieves a list of available emails along with their sizes
  • DELE – marks an email message for deletion
  • QUIT – Logs out and saves any changes made
  • STAT – Returns total number of messages and total size

Once the emails have been downloaded and deleted from the server, the client disconnects from the POP3 server. By understanding how POP3 works, users can effectively manage their emails and keep their mailbox organized.


Advantages and Disadvantages of POP3

POP3, one of the oldest email protocols, provides users with a number of advantages:

  • It is easy to set up and use, making it ideal for people of all levels of tech-savvy.
  • Emails are downloaded to your computer, allowing you to view them without an internet connection. 
  • Additionally, the attachments are already downloaded, which makes accessing them a breeze. 
  • Furthermore, POP3 requires less server storage space, as emails are stored on your device.

However, there are some drawbacks to consider when using POP3:

  • One key issue is the potential for your computer to become infected with a virus from an email attachment. 
  • Additionally, it is difficult to export your local mail folder to another email client or physical machine.
  • Finally, there is a risk of your email folders becoming corrupted, leading to the loss of all the data in the mailbox.

It is important to be aware of these downsides when using this email protocol.

Difference between SMTP, IMAP, and POP3

When comparing SMTP, IMAP, and POP3 protocols, it is important to understand the key differences between them. SMTP is a protocol used for transmitting emails in a client-to-server and server-to-server manner. In contrast, IMAP and POP3 are protocols designed for managing the inbox, functioning in a server-to-client mode.


SMTP and IMAP have distinct features, and it is important to emphasize their compatibility. These protocols do not compete with each other but complement each other, so there is no need to choose between them. The choice is between IMAP and POP3.

SMTP is the protocol responsible for sending emails from one server to another. IMAP provides users with the ability to access their emails stored on the server. IMAP allows users to access their emails from different devices while keeping the organization and synchronization of their messages consistent.

This means that users can access their mailboxes from different devices while still having the same view. So, if you need the flexibility to manage your emails on different devices, IMAP is the way to go. It is simple to use and provides a reliable and efficient way of accessing emails.


If you’re looking for a user-friendly experience, POP3 might be the right choice for you. It allows you to easily download all your emails from the mail server to your computer or mobile device. This means that once the emails are downloaded, you can access them even without an internet connection.

Unlike IMAP, POP3 deletes the messages from the server after they are downloaded. This gives you more control over managing your emails and allows you to store them locally.

POP3 is a great option if you want access to your emails even without an internet connection and are looking for more control over managing them. 

Choosing Between IMAP and POP3

Choosing the right email protocol for your needs and preferences can be overwhelming. To help you make an informed decision, consider the following factors:

Choose IMAP if you:

  • Have a reliable internet connection
  • Need access to mail from multiple devices
  • Want to organize your mail in folders or hierarchies
  • Have unlimited storage space on the server
  • With IMAP, you can also expect fast access to your emails.

On the other hand, POP3 is better suited for those who prioritize privacy. It offers the following advantages:

  • Stores email locally on your machine
  • Works best when the email account is used by a single user and device
  • Useful if you have a weak or unavailable internet connection

Deciding between IMAP vs. POP3 depends on your individual needs and preferences. Ultimately, the decision comes down to what works best for your needs. IMAP and POP3 provide different ways for users to receive emails, so consider factors like how you want to manage your mailbox and if you need access from multiple devices. On the other hand, SMTP is great for sending emails but does not offer any features for managing emails on the server.

How Emaillabs Can Help You With Email Protocols

EmailLabs offers services that rely on the widely supported SMTP (Simple Mail Transfer Protocol) protocol. With SMTP, you can seamlessly integrate our services into any email application. Simply update your application’s SMTP credentials and parameters, and you’re all set to start sending emails. It’s a hassle-free process that ensures your email communication is smooth and efficient. So, take advantage of the versatility and compatibility of SMTP with EmailLabs and unlock a world of possibilities for your email campaigns.

Maximize your email deliverability and security with EmailLabs!


Email protocols can be tricky to understand, but it’s important to know the differences between SMTP, IMAP, and POP3. Choosing the right protocol for your email can make all the difference. Consider your needs and preferences when deciding which one is best for you.

Email protocols are like the guardians of our digital messages, making sure they get delivered safely and without any sneaky hackers poking around. So, the next time you send or receive an email, take a moment to appreciate the importance of these protocols. They may be behind the scenes, but they play a vital role in keeping our digital communication running smoothly.

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