When you hit "Send," your email travels through a chain of servers, protocols, and checks in a matter of seconds before it appears in the recipient's inbox. The process relies on three core protocols: SMTP for sending, and IMAP or POP3 for receiving.
Understanding this journey helps you troubleshoot delivery problems, choose the right email provider, and set up professional email on solid ground.
Step 1: Your email client connects to the SMTP server
Everything starts in your email client — Outlook, Gmail, Thunderbird, or any similar app. When you click "Send," the client hands your message off to your outgoing SMTP (Simple Mail Transfer Protocol) server.
SMTP is the universal mail-sending protocol. It operates on port 587 (with authentication and TLS encryption) or port 465 (SMTPS). The SMTP server verifies your credentials before accepting the message.
- Your client opens a TCP connection to the SMTP server.
- TLS encryption is negotiated to protect data in transit.
- The client sends the message along with its headers: sender, recipient, subject, date.
- The SMTP server confirms receipt with a
250 OKresponse code.
Step 2: The SMTP server looks up the recipient via DNS
Your SMTP server now holds the message but needs to know which server to deliver it to. It queries the DNS (Domain Name System) for the MX records (Mail Exchanger) of the recipient's domain.
For example, if you send to [email protected], your server queries the MX records of example.com and gets the address of the mail server that handles it. If multiple MX records exist, they are used in priority order.
What happens if DNS fails?
If no MX record is found or the domain is misconfigured, your SMTP server returns a bounce — a delivery failure notification sent back to you. This is the most common cause of "undelivered mail" errors.
Step 3: Server-to-server delivery
Your SMTP server opens a new connection with the recipient's SMTP server (also called an MTA, Mail Transfer Agent) and transfers the message. This may involve several hops through relay servers along the way.
The first anti-spam filters are applied during this exchange:
- SPF (Sender Policy Framework): checks whether the sending server is authorized to send on behalf of the sender's domain.
- DKIM (DomainKeys Identified Mail): validates a cryptographic signature that proves the message wasn't tampered with in transit.
- DMARC: combines SPF and DKIM results and tells the receiving server what to do if either check fails.
Without these records properly configured, your emails risk landing in spam — or being rejected outright. At elenlace.com we configure SPF, DKIM, and DMARC for every business email setup we deploy.
Step 4: The receiving server stores the message
Once the recipient's SMTP server accepts the email, it passes it to the mailbox server (MDA, Mail Delivery Agent). The message is stored there until the recipient downloads or reads it.
| Protocol | Function | Standard port |
|---|---|---|
| SMTP | Message sending | 587 / 465 |
| IMAP | Synchronized mailbox access | 993 (SSL) |
| POP3 | Local mailbox download | 995 (SSL) |
Step 5: The recipient retrieves the message
The recipient's email client connects to the mailbox server using IMAP or POP3:
- IMAP syncs the mailbox on the server — messages stay there and can be accessed from multiple devices.
- POP3 downloads messages to the local device and removes them from the server (unless configured otherwise).
Today, IMAP is the recommended standard for professional use, especially when you check email across a computer, tablet, and phone.
Want your business email working seamlessly on all your devices? Browse our complete business email guide for the best options available.
Key takeaways
- Email sending uses SMTP; receiving uses IMAP or POP3.
- The SMTP server queries MX records in DNS to determine where to deliver the message.
- SPF, DKIM, and DMARC records are essential to keep your emails out of spam folders.
- IMAP is preferred over POP3 when accessing email from multiple devices.
- All traffic should be encrypted with TLS to protect your messages in transit.
Now that you understand how an email travels, the next step is making sure your domain is properly configured. Reach out to us at elenlace.com and we'll set up your business email with all the right DNS records from day one.
FAQ
How long does it take for an email to arrive?
Under normal conditions, email arrives within seconds. If the sending server has a queue or spam filters hold the message for review, delivery may take a few minutes. A permanent bounce is typically returned within minutes to hours — never wait days without checking your spam folder or bounce logs.
Why are my emails going to spam?
The most common causes are: missing SPF, DKIM, or DMARC records; sending from an IP with a poor reputation; content flagged by spam filters; or a newly created domain with no sending history. Setting up all three authentication records is the first step to fixing the problem.
What is an email bounce?
A bounce is a delivery failure notification. A hard bounce means the address doesn't exist or the domain is inactive. A soft bounce is temporary — a full mailbox or a downed server. After repeated soft bounces, most providers treat the address as a hard bounce.
Do I need to understand all this to have professional email?
You don't need to memorize every protocol, but understanding the flow helps you spot problems and communicate clearly with your provider. Choosing a reliable hosting service that configures SPF, DKIM, and DMARC for you is enough for most businesses.
Further reading
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