The Internet Message Access Protocol (IMAP) is a standard protocol used for accessing email messages on a remote server from a local client. IMAP allows email clients to retrieve email messages from a mail server over a TCP/IP connection, making it possible for users to access their emails from multiple devices such as desktop computers, laptops, smartphones, and tablets. This protocol is defined by RFC 9051.
IMAP is designed to enable complete management of an email box by multiple email clients. This means that email messages are generally left on the server until the user explicitly deletes them. This approach contrasts with the Post Office Protocol (POP), where emails are typically downloaded to a client and then removed from the server. IMAP’s ability to keep messages on the server and synchronize the state of an email box across different devices makes it particularly useful for users who access their email from multiple locations or devices.
An IMAP server usually listens on port number 143, while IMAP over SSL/TLS (IMAPS), which provides a secure connection, is assigned port number 993. IMAP supports various features that enhance email management, including the organization of messages into folders, flagging messages for urgency or follow-up, and saving draft messages on the server. It also supports multiple logins, allowing users to connect to the email server from different devices simultaneously.
IMAP provides a dynamic view of the mailbox, with the protocol requiring that external changes in state, such as newly arrived messages, be reported. This is in contrast to POP, which provides a static view of the mailbox. For users with many or large messages, IMAP’s usage pattern, which involves staying connected and downloading message content on demand, can result in faster response times.
The protocol has evolved over the years, with IMAP4 being the latest version. It was created to offer more flexibility and efficiency in email retrieval, catering to the needs of modern internet users who access their email across various devices. IMAP’s design allows for efficient email synchronization, making it an ideal choice for those who need to access their email on the go or using different devices.
In summary, IMAP is a crucial protocol for modern email communication, providing the flexibility, security, and efficiency needed for accessing and managing emails across multiple devices and locations.