HomeEmail EssentialsThe SMTP Servers - What SMTP Is And How It Works

The SMTP Servers – What SMTP Is And How It Works

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Godwin here. Why am I writing this? When I was thinking about a way to host and take control of my email marketing and autoresponder system, there wasn’t much information out there to guide me. Hence, I am writing this to offer assistance to anyone who finds themselves in the same position I was. Possibly, you’re one of them. If yes, then you’re in the right place.

But be warned: I’ll be discussing the complex technical operation of Simple Mail Transfer Protocol, so if that’s something you might not want to read, you may as well leave now. But if you’re still here, read with undivided attention so as to better understand. This is important because, with SMTP, you can avoid the high cost of autoresponder services and still execute your email marketing.

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Send Emails Without Autoresponder

The solution for sending emails without an auto-responder is using SMTP. I will be giving you an overview of how it works. If you’re ready, let’s go! Whenever you send a piece of email, your e-mail client (e.g., Eudora, Thunderbird, Outlook, etc.) interacts with the SMTP server on a webhost to handle the sending. The SMTP server on your host may converse with other SMTP servers to deliver the e-mail.

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If your database is bad, your server IPs are going to be blacklisted = NO INBOXING!

If you’re just spamming, the way I teach you in this blog post is not going to work = Don’t SPAM!

It’s a little expensive than subscriber based systems like Aweber & GetResponse. With Self hosted you pay per email. But if you’re doing it right, you’re going to make more than enough to cover the bills and make a healthy profit.

If you use Amazon SES, it will be cheaper because their rates per email are downright ridiculous. With other SMTPs, the rates vary.

SMTP Services Recommended:

1. Amazon SES  – Note: Avoid sending make-money online offers with SES.

2. Mandrill – Super cheap to send out emails, but make sure your data is squeaky clean & always include unsubscribe link.

3. SendGrid – Great delivery rates but a little expensive if you want to send millions of emails monthly. But if you’re sending highly relevant information only a few times per month, this is one of the best services on the planet.

I own and use all these services myself, and I don’t recommend anything that I don’t personally use on this blog.

Server Features

Get to know more about web server setup, essential hardware, and software

First, a quick overview of the features we’ll be getting from our modern email server:

  • Email storage is encrypted on the server.
  • Full encryption over the wire with TLS.
  • The server is locked-on-boot, and SSH on reboots to unlock.
  • Better SPAM detection.
  • Lightning-fast push support on all devices.
  • Full-text search that actually works.
  • Server software and all packages are open source.

Furthermore, our email server is built from a number of separate little projects that work together, including:

Postfix – the Mail Transfer Agent (MTA) that handles relaying mail between different servers. It decides what to do with email from the outside world and whether a particular user can send email using the server. Postfix hands off local delivery (that is, the actual saving of the mail files on the server) to Dovecot. Postfix also lets Dovecot take care of authentication before users are allowed to send email from the server.

Dovecot – the Local Mail Transfer Protocol service (LMTP), in email lingo, it essentially runs IMAP to handle requests from users who want to authenticate and check their email. Dovecot’s LMTP service functions as the Mail Delivery Agent (MDA) by saving mail files on the server. Dovecot also handles all authorization. It checks users’ email addresses and passwords in the MySQL database before allowing them to view or send emails.

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EncFS – this is used to encrypt our email store.

OpenDKIM—DKIM digitally signs all messages on the server to verify that the message was actually sent from the domain in question and is not spam or phishing.

MySQL – the database server stores lookup tables for domains, usernames and passwords, and aliases on the mail server.

Protips and caveats

Getting to know the vital functions of a web server is a necessary general knowledge

Congratulations for making to the end. I’m sure your brain must have had some exercise in trying to comprehend the ways of the Email as illustrated in the foregoing explanation. Go ahead and use your knowledge to host your own email campaigns.

For assistance in hosting your own email marketing campaign, contact us

For a complete down to earth guide on how you can successfully self-host your own independent autoresponder, click here

If you have been educated by the information contained in this write, do well to encourage us here by posting your opinion questions, or comments below. Thanks in anticipation.

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SMTP – How It Works

I would like to explain with a typical illustration. Let’s assume that I want to send a piece of e-mail. My e-mail ID is Godwin, and I have an account on aogodwin.com. I want to send an e-mail to [email protected]. I am using a stand-alone e-mail client like Outlook Express.

When I set up my email account at aogodwin.com, I told Outlook Express the name of the mail server — mail.aogodwin.com.com. When I compose a message and press the Send button, here’s what happens:

1. Outlook Express connects to the SMTP server at mail.aogodwin.com.com using port 25.

2. Outlook Express converses with the SMTP server, telling the server the sender’s and recipient’s addresses, as well as the message’s body.

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3. The SMTP server takes the “to” address ([email protected]) and breaks it into two parts: the recipient name (peacealeru) and the domain name (yahoo.com). If the “to” address had been another user at aogodwin.com.com, the SMTP server would hand the message to the POP3 server for aogodwin.com.com (using a little program called the delivery agent). Since the recipient is at another domain, SMTP must communicate with that domain.

4. The SMTP server has a conversation with a Domain Name Server, or DNS. It says, “Can you give me the IP address of the SMTP server for yahoo.com?” The DNS replies with one or more IP addresses for the SMTP server(s) that Yahoo operates.

5. The SMTP server at aogodwin.com.com connects with the SMTP server at Yahoo using port 25. It has the same simple text conversation that my e-mail client had with the SMTP server for aogodwin.com and gives the message to the Yahoo server. The Yahoo server recognizes that the domain name for peacealeru is at Yahoo, so it hands the message to Yahoo’s POP3 server, which puts it in peacealeru’s mailbox.

If, for some reason, the SMTP server at aogodwin.com cannot connect with the SMTP server at Yahoo, then the message goes into a queue. The SMTP server on most machines uses a program called sendmail to do the actual sending, so this queue is called the sendmail queue. Sendmail will periodically try to resend the messages in its queue.

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For example, it might retry every 15 minutes. After four hours, it will usually send you a piece of mail that tells you there is some sort of problem. After five days, most sendmail configurations give up and return the mail to you undelivered.

The SMTP server understands very simple text commands like HELO, MAIL, RCPT, and DATA. The most common commands are:

HELO – introduce yourself

EHLO – introduce yourself and request an extended mode

MAIL FROM: – specify the sender

RCPT TO: – specify the recipient

DATA – specify the body of the message (To, From, and Subject should be the first three lines.)

RSET – reset

QUIT – quit the session

HELP – get help on commands

VRFY – verify an address

EXPN – expand an address

VERB – verbose

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While you understand the operation and setup of SMTP servers, you may consider this list of email hosting providers.

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Here’s a summarized overview of how SMTP works:

  1. Client-Server Communication: When you compose an email and click “send” in your email client (such as Gmail or Outlook), the client software communicates with an SMTP server. Your email service provider or your organization typically provides this server.
  2. Establishing Connection: The client initiates a connection with the SMTP server on a specific port (usually port 25). This connection is typically established using the TCP/IP network protocol.
  3. Handshaking: Once the connection is established, the client and server perform a handshake process to verify each other’s identity and negotiate the details of the email transfer. This includes exchanging information about the supported authentication methods, encryption options, and the sender and recipient email addresses.
  4. Email Transfer: After the handshake, the client submits the email message to the SMTP server for delivery. This includes specifying the recipient’s email address, subject, message body, and attachments.
  5. Email Routing: The SMTP server analyzes the recipient’s email address and determines the appropriate destination server for the email. It does this by looking up the domain name (the part after the ‘@’ symbol) in the DNS (Domain Name System) to find the MX (Mail Exchange) records that identify the mail server responsible for that domain.
  6. Relaying: If the recipient’s email address domain differs from the sender’s, the SMTP server may need to relay the email to other servers to reach the final destination. This involves establishing connections with other SMTP servers in a chain until the email reaches the recipient’s mail server.
  7. Delivery or Storage: Once the email reaches the recipient’s mail server, that server stores the email in the recipient’s mailbox or forwards it to another email client for retrieval by the recipient.

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SMTP is a store-and-forward protocol, which means that if the recipient’s mail server is temporarily unavailable, the sending server will try again later until the message is successfully delivered or until it reaches a maximum retry limit.

It’s worth noting that SMTP is primarily used for sending emails. In contrast, other protocols like POP3 (Post Office Protocol version 3) or IMAP (Internet Message Access Protocol) are used for retrieving emails from mail servers.

Overall, SMTP servers play a crucial role in facilitating the transfer of email messages across different email systems and networks.

If you enjoyed this article, please help someone learn about these things by sharing it with your friends and followers on social media.

Also, don’t hesitate to tell us your opinion suggestion, or recommendation in the comment box below; doing so will encourage us to do more as well as further educate others about your viewpoint. Thanks in anticipation.

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