📨

How Email Works (SMTP)

Medium

Free preview · 2 of 7 steps

Email is a store-and-forward system

Unlike real-time chat, email is asynchronous. Messages are handed off between servers and stored until the recipient retrieves them.

The journey of one email: 1. Alice's client → her mail server (SMTP submission) 2. Her server → DNS lookup for destination MX record 3. Her server → Bob's mail server (SMTP relay) 4. Bob's client pulls from his server (IMAP/POP3)

Three protocols: SMTP (sending), IMAP (sync) or POP3 (download).

Packets in motion — click to inspect:

1 / 2

Space to play/pause · ← → to step