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How does email work?

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Quick answer

Email sends a message from your device to your provider's outgoing mail server using SMTP. That server finds the recipient's mail server and relays the message across the internet. The recipient's server stores it until their device fetches it using IMAP or POP. Shared protocols let any provider talk to any other.

Email works by sending a message from your device to your provider's mail server, which relays it across the internet to the recipient's mail server, where it waits until they download and read it. Shared protocols let any provider talk to any other.

Step by step

  1. You compose an email in your mail app and click send, which hands the message to your provider's outgoing SMTP server.
  2. Your SMTP server looks up the recipient's domain in DNS to find their mail server's address.
  3. Your server opens a connection to the recipient's server and transmits the message using SMTP commands.
  4. The recipient's server accepts the message and places it in the recipient's mailbox storage.
  5. When the recipient opens their mail app, it connects to the server via IMAP or POP to download and display the message.

Key things to understand

  1. Your message goes to your provider's outgoing mail server (SMTP).
  2. That server finds the recipient's mail server and delivers it.
  3. The recipient's device fetches it (via IMAP or POP).
  4. Addresses (you@domain) route mail like a postal system.

Labelled diagram

  1. Sender

    Composes email and clicks send in their mail app.

  2. Outgoing Server

    Sends the message using SMTP and looks up the recipient's server.

  3. Internet

    Carries the message between servers across networks.

  4. Incoming Server

    Receives and stores the message in the recipient's mailbox.

  5. Recipient

    Fetches the message via IMAP or POP to read it.

How an email travels from sender to recipient

Real-world examples

  • Sending a Gmail to a friend with an Outlook address: Gmail's SMTP server relays it to Outlook's server, which stores it until your friend logs in.
  • A university student emails a professor using the school's .edu address; the campus mail server delivers it to the professor's inbox on the same system.
  • You check email on your phone using IMAP: the phone syncs with the server, showing the same messages and folders as your laptop.
  • A company uses POP to download all emails to a single computer, so messages are removed from the server after retrieval.

Common mistake

✗ Myth: Email travels directly from your device to the recipient's device.

✓ Fact: Email is store-and-forward: it goes through at least two mail servers. Your device sends to your provider's server, which relays to the recipient's server, where it waits until the recipient retrieves it.

People also ask

How does an email get delivered?
Email delivery starts when you send a message from your device to your provider's outgoing SMTP server. That server uses DNS to find the recipient's mail server and relays the message there. The recipient's server stores it until the recipient's email client fetches it via IMAP or POP. This store-and-forward process ensures delivery even if the recipient is offline.
What is SMTP?
SMTP stands for Simple Mail Transfer Protocol. It is the standard set of rules for sending and relaying email between servers. When you send an email, your client uses SMTP to submit it to your outgoing server, which then uses SMTP to deliver it to the recipient's server. SMTP handles outgoing mail, not retrieval.
What is the difference between IMAP and POP?
IMAP and POP are protocols for retrieving email from a server. IMAP keeps messages on the server and syncs them across multiple devices, so you see the same inbox everywhere. POP downloads messages to one device and often deletes them from the server, which frees space but doesn't sync. IMAP is better for multi-device use, POP for single-device access.
What happens when you send an email?
It travels to your mail server, which relays it across the internet to the recipient's server, where it's stored until read.
Why can different email providers talk to each other?
They all follow shared open protocols (SMTP/IMAP), so Gmail, Outlook, and others interoperate.

Part of the guide: How the Internet Works →