Internet Message Access Protocol (IMAP)

The Internet Message Access Protocol (IMAP) is an important part of how email works today. It lets people check and manage their emails from different devices, like phones, tablets, and computers, without losing any updates.

Unlike the older Post Office Protocol (POP), which only downloads messages to one device, IMAP keeps everything in sync across all devices. This means if you read, delete, or move an email on one device, the changes show up everywhere. IMAP helps make email more organized, up-to-date, and easy to use no matter where you are accessing the data.

IMAP (Internet Message Access Protocol)

Internet Message Access Protocol (IMAP) is an application layer protocol that operates as a contract for receiving emails from the mail server. It was designed by Mark Crispin in 1986 as a remote access mailbox protocol, the current version of IMAP is IMAP4.

It is used as the most commonly used protocol for retrieving emails. This term is also known as Internet mail access protocol, Interactive mail access protocol, and Interim mail access protocol.

It retrieves messages from your email provider to your email client (such as on your Mac or PC). Importantly, it does not delete messages from the email service after you download them until the user explicitly deletes them.

It allows you to view and manage your emails across multiple devices because it synchronizes the emails between your email client and the server. This synchronization ensures that changes such as read status, deletions, and folder organization are reflected consistently across all devices connected to the same email account.

Features of IMAP

• Multi-Mailbox Management: It supports the management of multiple mailboxes, allowing users to organize their emails into various categories or folders.
• Message Flags: It provides the ability to add message flags, helping users keep track of the status of emails, such as whether they have been read.
• Selective Email Retrieval: It allows users to decide whether to download the full content of an email, or just retrieve the headers and decide later.
• Efficient Media Management: When multiple files are attached to an email, IMAP simplifies the process of downloading media files by handling attachments efficiently.

Working of IMAP

IMAP follows Client-server Architecture and is the most commonly used email protocol. It is a combination of client and server process running on other computers that are connected through a network.

This protocol resides over the TCP/IP protocol for communication. Once the communication is set up the server listens on port 143 by default which is non-encrypted. For the secure encrypted communication port, 993 is used.

• Port 143: Default non encrypted IMAP communication.
• Port 993: Secure IMAP communication with encryption (SSL/TLS).

The following steps are taken for the working of the IMAP :

• Email client Gmail establishes a connection with Gmail’s SMTP server.
• By approving the sender’s and recipient’s email addresses, the SMTP server verifies (authenticates) that the email can be sent.
• The email is sent to the Outlook SMTP server by Gmail’s SMTP server.
• The recipient’s email address is authenticated by the Outlook SMTP server.
• IMAP or POP3 is used by the Outlook SMTP server to deliver the email to the Outlook email client.

The following figure shows the working of the IMAP.

IMAP Working

Architecture of IMAP

The Internet Message Access Protocol (IMAP) protocol is a client-server model that allows users to access and view email messages stored on remote servers Here is a summary of the events:

• IMAP clients: An IMAP client is an email application or software that users use to communicate with their email accounts. Examples include Microsoft Outlook, Mozilla Thunderbird, Apple Mail, and mobile email applications. The client communicates with the server to receive, manage, and send email messages.

• IMAP Server: The IMAP server manages email messages and manages user mailboxes. It responds to requests from IMAP clients, and provides access to email folders and messages.
  The server stores emails in a structured format, usually organized in user-defined folders or mailboxes. Common IMAP server software includes Dovecot, Courier IMAP, Cyrus IMAP, and Microsoft Exchange Server.

• Network Protocols: It works over TCP/IP (Transmission Control Protocol/Internet Protocol) networks, and allows an client to connect to a server over the Internet or local area networks.

IMAP

Steps involve in IMAP Operation

• An email client, like Microsoft Outlook, connects to the server via IMAP when a user registers in.
• Certain ports are used for connections.
• The email client shows the headers of every email.
• It does not automatically download attachments, messages are downloaded to the client only when the user taps on them.
• Compared to alternative email retrieval protocols like Post Office Protocol 3, users can check their mail more quickly with IMAP (POP3).
• Until they are specifically deleted by the user, emails will stay on the server.
• While IMAP over Secure Sockets Layer (SSL)/Transport Layer Security assigns port number 993, the IMAP server listens on port 143.

Advantages

• It offers synchronization across all the maintained sessions by the user.
• It provides security over POP3 protocol as the email only exists on the IMAP server.
• Users have remote access to all the contents.
• It offers easy migration between the devices as it is synchronized by a centralized server.
• There is no need to physically allocate any storage to save contents.

Disadvantages

• IMAP is complex to maintain.
• Emails of the user are only available when there is an internet connection.
• It is slower to load messages.
• Some emails don’t support IMAP which makes it difficult to manage.