What Is IMAP? All You Need to Know About IMAP Servers

We send and receive dozens of emails daily. IMAP, an email protocol used for retrieving messages, is an essential part of email exchange. It allows you to access messages anywhere at anytime. In this article, understand what IMAP is, how IMAP servers work and why you should use them, and how the protocol stacks up against other email protocols.

What is IMAP?

IMAP, which stands for Internet Message Access Protocol, is a mail protocol used for retrieving email from email servers. But IMAP is somewhat different from other protocols because it allows you to access messages on an email server from multiple devices. For example, if you choose an email client such as Gmail, you can configure it with IMAP to retrieve the incoming emails on your phone, desktop computer, tablet and more.

The email app fetches your messages from the email server and pulls them into your inbox. Then you can easily view them, which is especially helpful if you receive emails in bulk daily as a part of your job or lifestyle.

Internet Message Access Protocol offers a great user email experience. The fact that it keeps your emails seamlessly in sync across all of your devices is a big plus. Internet Message Access Protocol offers more flexibility as it won't tie you to a single device. For this reason and others, all modern email clients and web servers support the protocol.

Graphic displaying the word IMAP (Internet Message Access Protocol) and small people around the letters

How does IMAP work?

Though emails can seem like a mystery, it's not too hard to learn how emails are sent, stored, and received. If you want to know how does IMAP work, the process is outlined below.

Initially, email clients use Simple Mail Transfer Protocol (SMTP) servers as an outgoing server to send messages to the recipient's mail server over a TCP/IP connection. Because SMTP is a push protocol and IMAP is a pull protocol, SMTP is the protocol in charge of sending mail.

After the mail sends, Internet Message Access Protocol defines how servers receive emails. The standard protocol follows a client-server model with an IMAP client on one side and an IMAP server on the other. Both processes run on different PCs connected through a network. Internet Message Access Protocol essentially acts as an intermediary between the email client and email server; when it connects to the server, it fetches the messages you request from the email server.

The server keeps the content, rather than your computer, and the server caches that content locally onto all of your devices. When you want to access remote message stores, the IMAP only downloads a copy of those messages. Next, it synchronizes anything done in or sent from your folders - whether sent items, drafts, deleted items, forwarded texts, or photos.

This helps your emails stay in sync. It also helps filter emails from any location. When you read an email, whether it be on your PC, your smartphone, or your tablet, the message will be exactly the same.

IMAP operation steps

This is the process for retrieving emails via IMAP:

  1. When you log into your email client, the client contacts the email server using IMAP.
  2. The TCP/IP connection links on a specific port. By default, IMAP uses port 143.
  3. The email client displays the headers of all emails in the folder.
  4. Emails or their attachments aren't downloaded until the user clicks on them.

Users can check copies of their messages quickly on different devices, and email messages are then kept on the server until you explicitly delete them. Note that you can also use the email header to trace an email if you receive an email which has origins you're unsure of.

An IMAP server uses two IMAP port numbers: port 143 and port 993. An IMAP server listens to the non-encrypted port 143 by default once the TCP/IP is established. Port 993 is then used by email clients to connect through IMAP securely; it's a secure port that works over TLS/SSL encryption for emails. Any other changes or alterations made to your emails are synced with the IMAP server.

Why use IMAP?

Most people use email every day. If you don't use an email app or client - like Microsoft Outlook, Yahoo! Mail, or Gmail - you need to specify your email protocol.

Internet Message Access Protocol is an excellent choice for email users. The protocol best fits most email-retrieval needs for these reasons:

  • It stores all emails on the remote IMAP server.
  • IMAP is a faster, more user-friendly Internet protocol compared to alternatives.
  • Users can connect to email accounts from multiple devices anytime.
  • It provides a reliable email experience.

Choosing IMAP over other protocols, like Post Office Protocol 3 (POP3), ensures users get the best experience with email - they get accessibility, speed, and flexibility.

Use IMAP if you need to access your messages from multiple devices, if you want to read your emails anywhere at anytime, if you want to sync emails, or if you must organize multiple mailboxes into categories, folders, or subfolders.

What is an IMAP server?

Internet Message Access Protocol allows you to access an email regardless of location. Oftentimes, users access these emails via the Internet because servers cache and store them. Whenever you sign into your account, the respective email client requests messages from the server.

When using the protocol, as mentioned above, you're not actually downloading the message to your PC. Instead, you view it directly from the server. Users can therefore read emails from any device hassle-free.

IMAP servers, meaning Internet Message Access Protocol servers, are therefore simply systems that process requests from an email client. Built to manage network resources, they store all incoming emails.

Good examples of IMAP mail servers include the Gmail server (imap.gmail.com), the Outlook server (imap-mail.outlook.com) and the Yahoo Mail server (imap.mail.yahoo.com).

Advantages and disadvantages of IMAP

There are a number of advantages and disadvantages to using Internet Message Access Protocol as an email protocol for retrieving emails.


Using Internet Message Access Protocol for your emails provides the following benefits.

  • Synced emails across all devices. Everything in the folder synchronizes with the IMAP server instead of a computer. The end result is that you'll access your messages even if your computer fails.
  • A faster email experience. Users can access, organize and sort emails quickly. Better than that, you don't have to download them first.
  • Greater flexibility. The protocol allows users to access their inboxes from multiple devices and different locations. This method is ideal for people who travel very often.
  • The ability to organize email messages on and off the server. You have flexibility; you don't need to be in a specific place or on a specific connection to organize messages.
  • Support from email clients. Most popular email clients like Outlook support the advanced features of the Internet Message Access Protocol.


Like all other protocols, Internet Message Access Protocol had flaws. Consider the following limitations or disadvantages to using the protocol.

  • Mandatory Internet connection. You need Internet access at all times to search, access and reply to your emails. Not being able to access your email history when you're offline can be a letdown, interfering with your convenience.
  • Need for more server space. You need to preserve more space on your server since everything caches there. If you run out of server space, you'll find yourself deleting old emails. However, choosing an email provider with sufficient server storage space is a viable solution.
  • Greater complexity. Internet Message Access Protocol servers are more complex to maintain than other email protocols like POP3.
  • More vulnerable to cyberattacks. Legacy emails like POP3, IMAP and SMTP are prime targets for black-hat hackers when the email servers get compromised. Cybercriminals are leveraging IMAP password attacks, but you can fix this through better configuration, multi-factor authentication mandates and SSL encryption.

IMAP security concerns

Though Internet Message Access Protocol is a frequently-used email protocol, it sometimes lacks sufficient security. Updates to the protocol addressed many security concerns over the years, but some still exist.

For example, Internet Message Access Protocol transmits users' personal details - such as their username, password, and history of email - in plaintext. Furthermore, IMAP lacks the sufficient support for strong authentication. There's been little advancement regarding the enforcement of multi-factor authentication (MFA).

Security professionals haven't been able to provide a mechanism that requires the user to use MFA when seeking Internet Message Access Protocol services. Furthermore, third-party email clients don't feel the need to move towards this; many don't support sign-on policies, leaving the door open for unauthorized persons.

IMAP security can improve through:

  • enabling multi-factor authentication for remote access
  • using firewalls to shut down remote users
  • ensuring properly-configured IMAP settings

These all can help protect against the attacks that the email protocol is potentially vulnerable to.

How to set up IMAP in Gmail

Many people use Gmail as their default email client. Some prefer to use other email clients like Microsoft Outlook or iOS Mail. However, if Gmail is your preferred client, IMAP can manage your incoming messages.

If you're wondering how to enable Internet Message Access Protocol within your Gmail account, it's fairly simple. Here's how to do it in a few steps:

  1. Sign in to your Gmail account on your desktop.
  2. Click Settings.
  3. Click See All Settings.
  4. Find Forwarding and POP/IMAP and scroll until you find the IMAP Access section.
  5. Select Enable IMAP and save your changes.

By doing this, you can comfortably access, read, and edit your emails without downloading them. IMAP will keep track of all incoming messages on the email server.

Frequently asked questions

What's the difference in IMAP vs POP3?

Both IMAP and POP3 are email protocols used by web-based email services to receive emails. However, the newer protocol Internet Message Access Protocol was designed to replace Post Office Protocol 3 (POP3).

Whereas IMAP can retrieve emails regardless of location, device, or time, POP3 downloads all new emails from the servers. Users can only read emails from the device on which they download the messages. With POP3, emails only exist on your local device and are deleted from the server.

Should you use IMAP over POP3?

Though many email servers still support both, IMAP serves as a superior option. It syncs all messages, whereas POP3 requires users to migrate folders to a new email app, requiring a migration tool. While POP3 conserves storage space, its successor ultimately reigns superior.

What does IMAP mean?

It means Internet Message Access Protocol.

Should I still be using POP3?

You can still use POP3, as it is supported by many email clients and services. The protocol works better for one dedicated device. Users who prefer having all emails accessible, even offline, should consider it.

What is the IMAP default number?

The default number is port 143. It's the default port number for Internet Message Access Protocol.