What Is IMAP?

IMAP is a standard way for an email app to access and manage messages in a mailbox stored on an email server. It allows the same mailbox to be used across different devices, so changes such as reading, moving or deleting an email can be reflected elsewhere when the mailbox synchronises.

What does IMAP mean?

IMAP stands for Internet Message Access Protocol. A protocol is simply an agreed set of rules that allows different systems to communicate with each other.

In this case, IMAP allows an email app to communicate with the server where your mailbox is held.

What does IMAP do?

IMAP allows an email app to access and manage your mailbox without treating the copy on each device as a completely separate mailbox.

For example, suppose you open an email on your phone. Later, you open the same email account on your computer. The message can already appear as read because that change has been recorded in the mailbox and can be seen by the other device.

The same principle can apply when you delete an email, move it into another folder or make other changes to the mailbox.

An email client is an app or program used to read and manage email. IMAP is one method an email client can use to communicate with the email service that holds your mailbox.

How does IMAP work?

At a basic level, the relationship looks like this:

Email provider and mail server ↔ IMAP ↔ email app on your phone or computer

Your email provider operates the servers where your mailbox is held. Your email app uses IMAP to access that mailbox and send mailbox changes back to the server.

This does not mean that an IMAP email app can never keep anything on your device. Apps may keep local or cached copies of messages so they load more quickly or can be available while you are offline. IMAP supports synchronising the mailbox again when the app reconnects.

For that reason, descriptions such as “IMAP stores your emails in the cloud” are not quite accurate. Your email service stores the mailbox. IMAP is the method the app can use to access and manage it.

What is IMAP used for?

IMAP is particularly useful when the same email account is accessed from more than one device or email app.

Instead of having a separate view of the mailbox on each device, the apps can work with the same mailbox held by the email service. Changes made through one device can then become available to the others when they synchronise.

This is why IMAP is commonly associated with using the same email account on a phone, computer and tablet.

IMAP vs POP3

IMAP and POP3 are both methods that email apps can use to access email, but they were designed differently.

The main difference between IMAP and POP3 is that IMAP is designed around accessing and managing a mailbox on the server, while POP3 is primarily designed to retrieve messages from the server, traditionally by downloading them to the device.

POP3 behaviour can vary depending on how an account is configured, so it is not accurate to say that POP3 always removes every downloaded message from the server.

IMAP vs SMTP

IMAP and SMTP perform different jobs.

IMAP is used to access and manage a mailbox. It is not the protocol responsible for sending an outgoing email.

Outgoing email normally uses SMTP, a separate protocol used to submit and transfer messages for sending.

Is IMAP secure?

IMAP can be used over an encrypted connection between your email app and the mail server. Modern email services normally use TLS, which protects the connection while information is travelling between the app and the server.

That does not mean IMAP provides end-to-end encryption for the emails themselves. IMAP is a way of accessing a mailbox, not an email-encryption system.

In normal use, the email provider and app usually handle the secure connection automatically.

Do I need IMAP?

You may already use email without ever seeing or configuring IMAP.

When you add an email account to another email app, the app will often try to configure the connection automatically without requiring you to enter IMAP settings yourself.

You are more likely to encounter the term IMAP if an email app asks you what type of account you are adding or requests incoming mail settings.

Exactly how this works depends on the email provider and the app. Some providers may require IMAP access to be enabled or configured in a particular way, while others handle it automatically.

For an ordinary email user, the important thing to understand is simply that IMAP allows an email app to work with a mailbox held on an email server and helps keep that mailbox consistent across devices.