4 stops. Every email. Every time.Four. Every email you have ever sent made the same four stops on its way to the inbox. Miss one, and your message bounces, stalls, or vanishes into spam. Let's ride along.
⬡ journey-flow, four nodes light up in sequence: Your MTA → DNS → Their MTA → Filters, an envelope waiting at the startStop one: your email app hands the message to an outbound mail server, called an MTA, short for Mail Transfer Agent. If you send from Gmail or Outlook, that's their server. If you use an email service, they run it for you. The MTA wraps your message in an envelope with the sender and recipient addresses, ready for the voyage.
⬡ journey-flow, envelope slides from a laptop icon to node 1 "Your MTA", an envelope wrapper animates around the message with To and From labels stamping onStop two: that MTA has to find out where the recipient's mail actually lives. It asks DNS, the internet's address book, "who accepts mail for thedeepsea.com?" DNS answers with an MX record, the name of the mail server that takes deliveries for that domain.
⬡ terminal, dig MX thedeepsea.com types itself out, the answer line appears: mail.thedeepsea.com, which then highlights in tealStop three: your MTA opens a connection to their MTA and passes the message over, a conversation in a protocol called SMTP. Three things can happen here. They accept it. They reject it outright, that's a hard bounce. Or they say "try again later," a soft bounce, and your server queues it up for another attempt.
⬡ journey-flow, envelope crosses from node 1 to node 3, then three outcome stamps animate one by one: green ACCEPTED, red REJECTED with the envelope flying back, amber TRY LATER with the envelope circlingYou control steps 1-3. They control step 4.Stop four happens entirely on their side. The receiving server runs your message through filters: your sender reputation, your authentication results, the content, how people have engaged with you before. Then it decides, inbox, spam, or quarantine. You don't control that decision directly. But everything you did in steps one to three feeds it.
⬡ journey-flow, envelope enters node 4, a scanner beam sweeps over it, then three doors appear: Inbox, Spam, Quarantine, the Inbox door opens and the envelope glides inOne more thing worth knowing: every server that touches your message stamps a Received header on top of it. They stack up like a ship's log, showing the exact route and how long each leg took. When mail goes missing, that log is where you look. Reading headers gets its own video, linked below.
⬡ header-inspector, a raw header scrolls, Received lines stack on top one at a time, each new line sliding in and briefly highlighting⬡ title-cardSo: hand-off, address lookup, server-to-server transfer, filter verdict. You steer the first three. The fourth is theirs to judge, based on how well you sailed the first three.
Next up: the actual systems doing each of those jobs, client, MTA, DNS, receiving MTA, who does what. Subscribe, we're answering every email delivery question, one at a time.
⬡ end-card, Subscribe + Next: "The systems that deliver your email" (001.005.002)Email delivery happens in four steps: your client hands the message to an MTA (Mail Transfer Agent), the MTA looks up the recipient's MX record in DNS, it hands the message to the receiving server over SMTP, and that server's filters decide inbox, spam, or quarantine. Plus the Received headers that log the whole trip.
Next: The systems that handle each step → [link 001.005.002]
Full written guide → [link 001.005.001]
#email #deliverability #smtp