IMAP

Server-Side Mail Storage

IMAP (Internet Message Access Protocol) is an email retrieval protocol that keeps messages stored on the mail server rather than downloading and deleting them locally. This allows you to access the same mailbox from multiple devices — phone, laptop, webmail — and see a consistent view of your email. Folders, read status, and flags are synchronized across all clients in real time through the server.

IMAP vs. POP3

The key architectural difference between IMAP and POP3Post Office Protocol version 3. An email retrieval protocol that downloads messages from a server to a single client, typically deleting them from the server afterward. Simpler but less flexible than IMAP. is where mail lives. POP3 downloads messages to the local device and typically deletes them from the server. IMAP maintains the server as the canonical store. IMAP also supports server-side search, partial message fetching (useful for large attachments on slow connections), and push notifications so clients know immediately when new mail arrives. For multi-device workflows, IMAP is almost always the better choice.

Protocol Details

IMAP operates over TCPTransmission Control Protocol. A reliable, connection-oriented transport protocol that guarantees ordered, error-checked delivery of data through three-way handshakes, acknowledgments, and retransmission. The foundation of HTTP, SSH, and most internet services. port 143 for plain connections and port 993 for IMAP over SSL/TLSSecure Sockets Layer / Transport Layer Security. Cryptographic protocols that provide encrypted, authenticated communication over a network. SSL is deprecated; modern implementations use TLS 1.2 or TLS 1.3. (IMAPS). It uses a tagged command-response model where each client command is prefixed with a unique tag so responses can be matched to commands even when multiple commands are in flight. SMTPSimple Mail Transfer Protocol. The standard protocol for sending email between servers and from clients to servers (port 25/587). SMTP handles outbound delivery, while IMAP or POP3 handle retrieval. handles sending mail, while IMAP (or POP3Post Office Protocol version 3. An email retrieval protocol that downloads messages from a server to a single client, typically deleting them from the server afterward. Simpler but less flexible than IMAP.) handles retrieval — the two roles are always separated in internet email architecture.