How an Email Travels From Sender to Inbox
A plain-language tour of what happens in the few seconds after you press Send.
When you press Send, a message seems to arrive instantly. Behind the scenes it makes a short journey across several systems. Knowing the steps helps you understand why emails are sometimes delayed, land in spam or bounce back.
Step 1: Your email program hands the message to your mail server
Your email app, such as a phone app or a web page, connects to your provider's outgoing mail server and passes the message over. This server is sometimes called an SMTP server, after the protocol it uses.
Step 2: The server looks up where to deliver it
Your server reads the part of the address after the @ sign, for example the domain in name@example.com. It then asks the Domain Name System, which works like a phone book for the internet, for that domain's MX record. The MX record names the mail servers that accept email for that domain.
Step 3: The message is delivered to the receiving server
Your server connects to the receiving server and sends the message. This is where SPF, DKIM and DMARC records matter. The receiving server uses them to check that the message really comes from where it claims to and has not been changed.
Step 4: Filters decide what happens next
The receiving server runs the message through spam and malware filters. Based on the results, it places the message in the inbox, moves it to spam, holds it for review or rejects it. Reputation matters here: servers that send lots of unwanted mail get treated with suspicion.
Step 5: The message waits for the recipient
The message is stored in the recipient's mailbox. When the recipient opens their email app, the app collects it from the server using a protocol such as IMAP or the web interface, and it appears on screen.
Why things go wrong
If the receiving server is down, your server keeps retrying for a while, which causes delays. If the address does not exist, you get a bounce message. If the sender's domain lacks proper records or has a poor reputation, the message may land in spam.
What you can do
If you run your own domain, make sure your MX, SPF, DKIM and DMARC records are set correctly. Send from a reputable provider. Avoid sending large attachments, and use a clear subject line. These steps keep your messages arriving where you want them.