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system-design-101/data/guides/how-is-email-delivered.md
Kamran Ahmed ee4b7305a2 Adds ByteByteGo guides and links (#106)
This PR adds all the guides from [Visual
Guides](https://bytebytego.com/guides/) section on bytebytego to the
repository with proper links.

- [x] Markdown files for guides and categories are placed inside
`data/guides` and `data/categories`
- [x] Guide links in readme are auto-generated using
`scripts/readme.ts`. Everytime you run the script `npm run
update-readme`, it reads the categories and guides from the above
mentioned folders, generate production links for guides and categories
and populate the table of content in the readme. This ensures that any
future guides and categories will automatically get added to the readme.
- [x] Sorting inside the readme matches the actual category and guides
sorting on production
2025-03-31 22:16:44 -07:00

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How is Email Delivered? Explore the journey of an email, from sender to receiver, step by step. https://assets.bytebytego.com/diagrams/0185-email-deliver.png 2024-02-28 false
how-it-works
EmailProtocols
EmailDelivery

Do you know how an email is delivered?

When I first learned how similar email is to traditional snail mail, I was surprised. Maybe you will be, too. Allow me to explain.

In the physical world, if I want to send a postcard to a friend, I would put it in a nearby mailbox. The postal office collects the mail regularly and relays it to the destination postal office. This postal office then puts the postcard in my friends mailbox. This process usually takes a few days and my friend receives my gratitude in paper form.

Email functions in a similar way. The terminology changes because it is an internet-based solution, but the fundamentals are the same:

  • Instead of putting mail in a mailbox, the sender pushes an email to the Sender Mail Server using MUA (mail user agent,) such as Outlook or Gmail.

  • Instead of using postal offices to relay mail, MTA (mail transmission agent) relays the email. It communicates via the SMTP protocol.

The email is received by the Receiver Mail Server. It stores the email to the Mailbox by using MDA (mail delivery agent.) The receiver uses MUA to retrieve the email using the POP3/IMAP protocol.