How does email actually work (simplified)?

You click "Send" and seconds later, your message is in someone else's inbox. Simple from your side. Not so simple behind the scenes.

Here's what's actually happening: your email client (whether that's Gmail, Outlook, or Fastmail) hands the message to an SMTP server. SMTP stands for Simple Mail Transfer Protocol, and it's the protocol that moves email between servers. Your provider's SMTP server is the first stop.

That server now needs to figure out where to deliver your email. It looks at the recipient's address (let's say kraken@thedeepsea.com) and queries DNS (Domain Name System) to find the mail server responsible for thedeepsea.com. DNS returns something called an MX record, which is basically the address of the recipient's mail server.

Your provider's server then connects to the recipient's server and hands off the message. This is still SMTP at work. Server-to-server, following the same protocol rules that have existed since the 1980s. The recipient's server accepts the message and stores it in their inbox queue.

Now the recipient's side: when they open their email client, it connects to their mail server using either IMAP or POP3. IMAP keeps the email on the server and syncs across devices. POP3 downloads it and (usually) deletes it from the server. Either way, the recipient sees your message.

What makes this work across every email provider is that they all follow the same protocols. SMTP for sending, IMAP or POP3 for retrieval. Gmail can talk to Outlook, Fastmail can talk to Yahoo Mail, because they're all using the same navigation charts.

One more thing worth knowing: between clicking "Send" and the message landing in the recipient's inbox, there are authentication checks, spam filters, and reputation lookups happening. Your message is being inspected at multiple points. But the basic path? Client → SMTP server → DNS lookup → recipient's server → recipient's client. That part hasn't changed in decades.

If you're curious about any one piece of this (authentication, DNS setup, how spam filters decide), the Email Almanac has you covered. Or just ask us directly if something's breaking.