/ˈaɪ-mæp/
n. “Check your mail without moving it.”
IMAP, short for Internet Message Access Protocol, is a standard protocol used by email clients to retrieve messages from a mail server. Unlike older protocols that download and remove emails from the server, IMAP allows users to read, organize, and manipulate their messages while keeping them on the server, providing a consistent view across multiple devices.
Developed in the 1980s as an improvement over POP3, IMAP enables synchronization between clients and server, letting users access the same mailbox from desktops, laptops, tablets, or smartphones without losing track of messages. Actions like marking as read, moving to folders, or deleting are reflected across all connected clients.
IMAP supports multiple folders, server-side search, and partial message retrieval, allowing users to preview headers or download just the body of an email. It operates over TCP and typically uses port 143 for unencrypted connections or 993 for encrypted connections via TLS or SSL.
One practical example: a user checks email on a work laptop via IMAP, then later views the same inbox on their phone. Messages marked as read on one device are automatically marked as read on the other. Any organizational changes, like moving a message to a folder, are preserved across all devices because the server maintains the authoritative state.
Modern email providers, including Gmail, Outlook, and Yahoo, use IMAP as the default method for external clients, ensuring seamless multi-device access and centralized message management. It also facilitates backups and archiving since messages remain on the server rather than being scattered across individual devices.
Security is paramount: IMAP is often combined with TLS encryption to protect credentials and message contents in transit. Many organizations enforce encrypted connections to prevent eavesdropping and unauthorized access.
In comparison to POP3, which downloads and often deletes messages from the server, IMAP shines in collaborative environments or for users who need consistent access from multiple endpoints. It aligns with modern workflows where email is a shared, cloud-based resource rather than a locally stored artifact.
IMAP does not define message storage formats; it works in conjunction with formats like MIME for attachments and encoding, ensuring emails can carry text, images, and other content reliably across systems.
In short, IMAP is the backbone protocol for modern multi-device email access: efficient, centralized, and synchronized, giving users control and continuity while maintaining the mail on a single authoritative server.