GCSE · Computer Science · AQA · Spec 8525

IMAP

You read an email on your phone on the bus. When you get home, your laptop already shows it as read. How does the laptop know?

Computer Science · Networks

One mailbox, two devices

Three emails arrive: Kit, Gig and Quiz (● means unread). You check the same account on a phone and a laptop, and both use IMAP. Step through what you do, and keep an eye on the Server column.

Predict first: if you delete an email on your phone, will it still be on your laptop?

Server mailbox	Phone shows	Laptop shows
●Kit ●Gig ●Quiz	●Kit ●Gig ●Quiz	●Kit ●Gig ●Quiz

Output

Requests to the server:

Step 1: Three new emails are sitting in your mailbox on the mail server. Your phone and your laptop have each downloaded copies so they can show them to you. The emails themselves haven’t gone anywhere: they’re still on the server.

1 / 7

Press Next, one step at a time. Each time you do something, which column changes, and which one is left behind?

Step 1 of 7: Three new emails are sitting in your mailbox on the mail server. Your phone and your laptop have each downloaded copies so they can show them to you. The emails themselves haven’t gone anywhere: they’re still on the server..

Watch out: Easy mistake: thinking IMAP moves your emails onto the device. It doesn’t. Each device downloads copies to show you, and the emails themselves stay stored on the server.

Computer Science · An email’s journey

Who does which leg?

So how does an email get into that mailbox in the first place? Ava emails Ben. Put these stages of that one email’s journey in order, from the moment it’s written to the moment Ben gets at it.

1 · First5 · Last

The email waits in Ben’s mailbox on his mail server
Ben’s email app accesses the email on his mail server
Ava writes the email in her email app
Ava’s mail server passes the email to Ben’s mail server
Ava’s email app sends the email to her mail server

Computer Science · Structure

Where IMAP sits in the TCP/IP model

One last thing to place: where IMAP sits in the layers of the TCP/IP model. Tap each layer, starting at the top.

Tap any part of the diagram to see what it does.

Computer Science · Put it in your own words

Explain it like you’d write it

Jamal checks the same email account on his phone and on his laptop. Explain why IMAP suits him. [3 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

His emails stay stored on the mail server, rather than being moved onto one device. (1 mark)
Each device downloads copies of the messages to display them, so he can read his email on either. (1 mark)
Actions such as reading, deleting or moving a message are carried out on the server, so both devices stay synchronised and show the same mailbox. (1 mark)

Model answer

With IMAP, Jamal’s emails stay stored on the mail server instead of being moved onto one device. His phone and his laptop each download copies of the messages to display, so he can read his email on either one. When he reads, deletes or moves a message on one device, that action is carried out on the server, so the other device shows the same, synchronised mailbox.

Three moves make a full answer: where the emails are (on the server), what the device gets (copies), and why the devices stay in step (every action happens on the server).

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Your emails don’t live on your phone. They live on a server, and every device you use is a window onto them.

What you need to know

IMAP stands for Internet Message Access Protocol. It’s the protocol an email client (your email app) uses to access and retrieve email messages stored on a mail server.
With IMAP, the messages stay stored on the mail server. Your device downloads copies to display them. It doesn’t remove them from the server.
Because the messages are kept on the server, the same mailbox can be used from several devices and they stay synchronised. Reading, deleting or moving a message into a folder is carried out on the server and seen on every device.
IMAP is for receiving and accessing email. SMTP is the protocol that sends email, from a client to a mail server and between mail servers.
IMAP is an application-layer protocol in the TCP/IP model. It relies on the lower layers (transport, internet and link) to deliver its data.

The big picture

IMAP (Internet Message Access Protocol) is the protocol an email app uses to access emails stored on a mail server. The emails stay on the server, and your device downloads copies to show you. Every action you take, whether reading, deleting or moving a message into a folder, is carried out on the server, so every device you use shows the same mailbox. IMAP is for accessing email and SMTP is for sending it. IMAP works at the application layer of the TCP/IP model.

Key points

1The mailbox lives on the server. Your devices show copies.

2Act on one device, it happens on the server, and every device shows it.

3SMTP sends. IMAP accesses.

4IMAP is application layer, and it relies on transport, internet and link beneath it.

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Worked example

Problem

Priya reads her email on her phone using IMAP. She loses the phone, then signs in to the same email account on a new phone. Explain whether she will still see her emails, including the ones she had sorted into folders.

⚠ Watch out

Saying IMAP moves emails onto your device, or that IMAP sends email. IMAP accesses emails that stay on the server, and SMTP is the protocol that sends.

🧠

Memory hook

SMTP is the delivery van that brings your post to the mailbox. IMAP is a window onto that mailbox, and you can look through it from any device. Looking doesn’t take the post away, so every device sees the same mailbox. (Where the picture stops working: your device does download copies to show you. The real messages still never leave the server.)

✓

Check yourself

What would go wrong if IMAP moved each email onto whichever device opened it first? Think about what your laptop would show after you’d read your emails on your phone.

Flashcards

(9)

What does IMAP stand for?

Internet Message Access Protocol.

What is IMAP used for?

It’s the protocol an email client uses to access and retrieve email messages stored on a mail server.

With IMAP, what does your device download, and what stays on the server?

Your device downloads copies to display. The messages themselves stay stored on the mail server.

Name three actions that IMAP carries out on the server, not just on your device.

Reading a message, deleting it, and moving it into a folder.

Why do all your devices show the same mailbox with IMAP?

Each action is carried out on the server, and every device shows what’s on the server. So they stay synchronised.

Which protocol sends email?

SMTP. It sends email from a client to a mail server, and between mail servers.

Which leg of an email’s journey uses IMAP?

The last one: the recipient’s email app accessing the message stored on their mail server.

Which layer of the TCP/IP model does IMAP work at?

The application layer.

Which layers does IMAP rely on to deliver its data?

The lower layers: transport, internet and link.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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One mailbox, two devices

Who does which leg?

Where IMAP sits in the TCP/IP model

Explain it like you’d write it

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