How does email really work?

This article is intended to explain how email works in basic terms, without sounding too technical. Regardless of whether you are a beginner or someone looking to refresh their knowledge, this has got you covered!

It goes without saying that email is one of the most essential tools of communication. Sending an email is a simple task – type in a recipient’s email address, add a subject line, draft the message and hit send. But have you ever wondered how emails reach their destination? This article is intended to explain how email works in basic terms, without sounding too technical. Regardless of whether you are a beginner or someone looking to refresh their knowledge, this has got you covered!

A brief history of email

Email is a vital part of our daily communication routine, but it wasn't always this way. The first email ever sent was in 1971 by a computer engineer named Ray Tomlinson, and at this time, email was mainly used by academics and researchers in select universities and government agencies. However, with the arrival of the internet and web-based email services like Hotmail and Yahoo in the 1990s, email became widely accessible to the public. Today, email is an essential tool for business and personal communication, allowing individuals to send and receive messages, share files, and stay connected. 

How email is sent around the internet

Sending the email

Sending an email is a seemingly simple process, but there's actually quite a bit going on behind the scenes, and here we will break down this process into simple steps – it seems like a lot is going on but this whole process could take just a matter of seconds.

  • First you need to of course compose your email using your favorite email client e.g. Gmail, Outlook and Apple Mail are among the most popular. You will add the recipient’s email address, a subject line they won’t be able to miss, and of course an engaging message in the body of your email.


When you hit “Send”, this is when all the magic starts to happen…   

  • Your email client connects to your email service provider’s SMTP server.

  • Then your SMTP server will verify your details to make sure that everything is as it should be, and that you are in fact who are claiming to be.  

  • The email is then formatted by Gmail/Outlook or whatever your chosen email client is, and includes the header of the email, the body content of the email, the footers and any of course any attachments you’ve sent with your message. 

  • Your email client (remember, Gmail or Outlook etc.) sends this email to your SMTP server using the SMTP protocol.  

  • Your SMTP server will perform a DNS (Domain Name System) search to find the recipient’s email server – this is like looking up a contact in what acts like a ‘internet phonebook’, and it turns the address into an IP address. 

  • What’s next is that your SMTP server then makes a connection with the recipient’s SMTP server using the IP address which was found in the DNS ‘phonebook’ search.


Receiving the email

Okay, so we’ve sent the email… remember this is happening in seconds! It’s now time to get it in the hands of the person that’s going to read the email.  

  • The first step in receiving the email, is that the recipient’s SMTP server will verify your SMTP server and performs checks to make sure that you aren’t sending them anything that could be marked as Spam or malicious.  

  • The next thing that will happen is that your SMTP server transfers the email to the person receiving the email’s SMTP server. It uses the SMTP protocol to transmit the email across.  

  • The recipient’s SMTP server now delivers your email to the recipient’s mailbox on their email server, and they can access and open their mailbox on their email client – Outlook, Gmail, Apple Mail etc.

  • Now recipient can do whatever they want with this email – it probably depends on what the email is about, but they can read it, send you back a reply, forward it on to someone else or they can delete the message. Let’s hope they don’t mark it as spam!

When it goes wrong – issues affecting email deliverability

Have you ever had anyone say to you – “I never got your email…” It can happen, and here we will look at why this can happen, and what can affect email deliverability.

There are a number of issues that can affect this process including: 

  • IP reputation/blacklisted IP 
  • Domain reputation 
  • Spam filters
  • Not configuring and implementing authentication protocols  
  • Content and formatting problems
  • Unengaged subscribers  
  • High bounce rate  
  • High number of complaints  
  • A sudden increase in number of emails being sent.

In this last section, we will look at these issues in more detail and outlines both best practices for improving deliverability as well as what steps you should take if delivery fails for some reason. 

Read on to find out all you need to know about keeping your emails from going missing in cyberspace!

Poor IP reputation/blacklisted IP

What’s the problem?

Having a poor IP reputation, also known as having a blacklisted IP, occurs when your IP address has been flagged as a source of spam or malicious activity. This can affect your email deliverability in a negative way and cause your messages to be blocked or sent to spam folders. It usually happens when your IP address has been hacked or compromised in some way and/or it’s been used for inappropriate activities such as phishing or sending bulk unsolicited emails. 

How to fix it

To fix a blacklisted IP, you’ll need to do some digging to understand the cause of the problem and take the necessary action to make it right. This may include removing any malware or cleaning up your email list to make sure you’re not sending anything that could be interpreted as spam. Working with a reliable email service provider and regularly keeping an eye on your email activity can help maintain a positive IP reputation and ensure your messages get to where they are supposed to.

Domain reputation

What’s the problem?

Domain reputation is a crucial part of email deliverability. Things that can have a negative effect on domain reputation include email engagement rates, email volume, and spam complaints. If a domain has a poor reputation, emails coming from it, may end up in the recipient's spam folder or not even get delivered at all. 

How to fix it

To fix domain reputation, it's important to focus on improving email engagement rates, such as by providing valuable content and encouraging recipients to act. Monitoring any email campaigns for high bounce rates, sending emails only to opt-in recipients, and promptly handling spam complaints can also help maintain or improve domain reputation.

Spam filters

What’s the problem?

Spam filters are the first line of defense against annoying, misleading, and through to even dangerous emails. Among the most frequent reasons for blocked or filtered emails are the use of spammy sounding words, excessive use of capitalization, numbers and punctuation usage, and suspicious looking links. 

How to fix it

To improve your email delivery rates, avoid sounding too promotional, never use language that could be misunderstood as threatening, make sure you have permission to email the recipient, and use clear and relevant subject lines.

Not configuring and implementing authentication protocols

What’s the problem?

Authenticating protocols, such as SPF and DKIM, have a direct link with the effectiveness of email communication. Understanding the relationship between these protocols and being blocked is crucial for any business that relies on email to communicate with clients, customers, or partners. Sender Policy Framework (SPF) ensures that emails are sent from reputable and authentic sources. Meanwhile, DomainKeys Identified Mail (DKIM) is designed to prevent email spoofing and enhance email validation by verifying the authenticity and integrity of the message. When these protocols are not implemented or correctly configured, emails can be blocked by internet service providers (ISPs) and email providers. The result often interrupts business operations and hurts brand reputation.

How to fix it

To fix these issues, it's important to double-check that SPF and DKIM records are correctly set up and match the sending domain. Additionally, ensure that email service providers have been authorized to send on behalf of the sender's domain through SPF. With diligent attention to detail, these issues can be resolved to ensure successful email delivery.

Content and formatting

What’s the problem?

Email deliverability is affected by both content and formatting. The quality of your emails can determine whether they reach your customer's inbox or not. Email providers have spam filters and algorithms that look at the quality of emails before deciding to send them to the inbox or to the spam folder. Poor content and formatting of your emails can trigger these filters.

How to fix it

A way to prevent the content and formatting of your emails triggering spam filters is to make sure that you are sending quality content and that your emails are well designed, that templates aren’t broken and that images are optimized for email and not too large. 

High bounce rate

What’s the problem?

Sending email campaigns to unengaged subscribers can negatively impact email deliverability. Unengaged subscribers are those who haven't opened or clicked your emails in a while. If a high number of your subscribers are unengaged, it sends a signal to email providers that your content is not relevant to your audience, and they may start sending your emails to spam folders.

How to fix it

To fix this, you can segment your email list and send re-engagement campaigns to those who are considered unengaged. Personalize your emails with incentives to encourage subscribers to open and engage with your content. Another solution is to simply remove unengaged subscribers from your list entirely. This will over time, improve your overall engagement rates and help keep your emails out of spam folders.

High number of complaints

What’s the problem?

When too many users report a company's emails as spam or unwanted, it could lead to a high number of complaints. This can have negative effects on email deliverability because internet service providers (ISPs) monitor these complaints and may start to route the emails to the spam folder or even block them altogether. The reasons for a high number of complaints could be sending too many emails, sending irrelevant content, not having clear opt-in/opt-out options, or not properly segmenting the recipient list.

How to fix it

To fix this issue, you should always make sure you have clear opt-in consent from your audience that they want to receive emails from you, you should segment you emails to your various different audiences and make it easy for users to opt-out from your email should they wish to.

A sudden increase in number of emails being sent.

What’s the problem?

A sudden increase in the number of emails being sent from a specific server/IP address, can have a negative impact on email deliverability. This is because email providers use various filters to look for spam and if a sudden increase of emails is being sent from a particular domain, the filters may make the judgement that the emails are spam and send them to the spam folder or even block them from being delivered altogether. 

How to fix it

There is a simple fix to this problem, and you should always avoid sending too many emails at once and instead spread them out over time. Most ESPs do this for you so hopefully this shouldn’t be an issue.

As we can see, email has come a long way since it first became a daily aspect of our lives. From bouncing between mail servers to being delivered in seconds across the globe, modern technology has made the delivery process even more efficient than ever. 

In short, through recognizing the steps above, we can ensure that our messages find their destination quickly and smoothly on the internet.

Mailosaur is a tool that will make sure that all your customer communication arrives as it should, when it should. For more information about how it could work for you, check out our documentation here.