What's the difference between SMTP, IMAP, and POP3?

The email ecosystem relies on distinct protocols for sending and receiving messages. While SMTP handles transmission, IMAP and POP3 are the primary protocols for mail retrieval.

POP3 (Post Office Protocol 3) is a simple, stateless protocol for retrieving email. A client connects to the server and downloads messages to the local machine. While it can be configured to leave mail on the server, POP3 does not synchronize state (like read status or deletions) across clients, making it poorly suited for multi-device access.

IMAP (Internet Message Access Protocol) offers a more complex and stateful model. It allows a client to access and manipulate messages directly on the server. Because the email is stored server-side, any changes (e.g., marking as read, deleting, moving to a folder) are synchronized and reflected across all connected clients, providing a consistent view of the mailbox.

The key distinctions are:

• SMTP: A push protocol for sending email.
• POP3: A pull protocol that downloads and often deletes mail from the server.
• IMAP: A pull protocol that synchronizes client state with messages stored on the server.