What is IMAP?

IMAP (Internet Message Access Protocol) is an application-layer protocol used to work with email directly on the mail server.

In short: IMAP lets you read and manage mail on the server, rather than downloading it entirely to a device.

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#Why IMAP is needed

IMAP is used when you need to:

• work with mail from multiple devices
• see the same messages on your phone, laptop, and webmail
• store messages on the server
• sync the state of messages

That is why IMAP is the default standard in modern mail services.

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#How IMAP works (simplified)

1. The mail client connects to the server
2. It authenticates
3. The client:

• requests a list of messages
• reads messages
• marks them as read
• moves them between folders

4. All changes are saved on the server

The client only receives the data it needs, not all the mail at once.

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#IMAP's main trait

Mail is stored on the server, and the client is just a "window" for viewing it.

This means:

• the same message is visible on every device
• folders and labels stay in sync
• the "read / unread" status is the same everywhere

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#IMAP vs POP3 (short and simple)

• IMAP
  • messages on the server
  • suits multiple devices
  • state syncing
• POP3
  • messages are downloaded to the device
  • more often deleted from the server
  • poorly suited to multiple devices

If an interview asks "which one would you choose?", IMAP is almost always the right answer.

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#IMAP security

Classic IMAP:

• does not encrypt data

In practice people use:

• IMAPS (IMAP + SSL/TLS)

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#A real-life example

IMAP is like cloud storage for mail:

• messages live "in the cloud"
• you log in from any device
• you see the same mailbox