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The Email Marketer's Guide to Deliverability

August 15 - 2023

E-book 5 min read

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Email deliverability, it’s not the most exciting area of email marketing. But it is one of the most critical.

That’s because if your emails aren’t landing in the inbox, all of your hard work on email strategy, creation, and send will go to waste. As well as problematic deliverability causing significant issues in your ongoing email sends.

That’s why we’ve created an entire guide dedicated to email deliverability, exploring everything you need to know. From why deliverability matters and what good email deliverability is, to actionable best practice steps and our recommended tools.

So, whatever your knowledge of email deliverability, we’ve got you covered.

What is email deliverability?

Let’s begin with a definition of email deliverability, to ensure we’re all on the same page.

Email deliverability refers to the ability of an email communication to land in the intended recipient’s inbox. This is opposed to it bouncing, landing in the junk or spam folders, and even identifying if it lands in the promotions or social tabs.

Email deliverability rate is calculated by taking the number of delivered emails, and dividing this by the total number of emails sent. You can then multiply this number by 100 to get your percentage rate.

Deliverability rate = (delivered emails / total sent) x 100

Why does email deliverability matter?

Of course, it’s frustrating when any email communication doesn’t get to the recipient. And this can be far more consequential for critical emails such as password resets, transactional communications, or system downtime notifications.

Unfortunately, only 79.6% of legitimate emails reach their final destination. Meaning that 3 out of every 20 users, or a significant 15,000+ users in a seven-digit community, are missing emails that could be critical to both them and your business.

The knock-on effect?

For software businesses, users may struggle to access their account, or be notified of downtime, and therefore abandon your platform.

For B2C consumers, they will be left unaware of the exciting new products that you have tailored to their requirements.

Overall, consumers will be less aware of your brand and therefore less likely to purchase from you.

What is good email deliverability?

Questions like this are similar to “what’s a good open rate?” or “when is the best time to send an email?”.

The answer? It depends!

Each business will have so many different variables that a good deliverability rate is specific to them and their industry. However, to get the best results from your marketing campaigns it is recommended that you aim for a deliverability rate of between 85% and 95%. However, we would always recommend researching your industry to understand how other similar businesses perform in terms of deliverability. As well as analysing your own email engagement rates to set targets specific to you, and understand your results in full.

What affects email deliverability?

Deliverability is complex, consisting of lots of influential variables, some less obvious than others. Here are four particularly important factors that you should be aware of when it comes to deliverability health.


The back end of your email communications plays a significant role in deliverability.

The servers, setup, controls, and authentication used by a business’ email service provider (ESP) impacts how mailbox providers will view emails, and in turn place them in the inbox.

Fortunately, any good ESP will automatically authenticate the IP addresses and domains which are used by their customers to send email. Additionally, ensure that your ESP is authenticating emails with both SPF and DKIM standards, and setting up DMARC records for improved deliverability.

Email send volume

In short, the more emails you send, the more you are likely to be watched by mailbox providers. Which usually means as you send higher volumes, it becomes more challenging to maintain good deliverability compared to smaller senders.

Because of this your sending patterns are particularly important. Spammers have given email marketers a bad name, therefore avoid any activity that could be flagged as ‘spam’. This includes sending large volumes of emails randomly.

Instead, focus on building a predictable pattern of emails, with send volumes increasing over time. This tactic is particularly useful when ramping up to higher email frequency seasons, such as holidays or product launches.

Content and code

One straightforward variable that you can manipulate for improved deliverability is your email content.

It’s always important to pay attention to your image-to-text ratio, and the type of words you use. However, today inbox providers pay most attention to the content in the form of email code.

This includes ensuring that there is no potentially malicious code within the email, such as <embed> tags or JavaScript. Secondly, inbox providers favour emails that boast proper, clean code, with all tags closed. URLs are also particularly consequential for deliverability. Any emails that include links to websites that have poor reputation, or have used a URL shortener, may suffer in terms of deliverability.

Poor list health

Getting subscriber acquisition right is essential for both email engagement and deliverability. And it’s something that mailbox providers are particularly hot on.

Lists which are bought from third parties, are left to stagnate, or are not regularly cleaned can result in hard bounces and spam complaints. Even worse, there may be spam traps included in unhealthy lists. These are email addresses used by inbox providers and blocklist operations specifically to catch spammers. So, by sending to just a few of these spam traps, you can immediately negatively impact your deliverability rate.

Steps to best practice email deliverability

Now that we’re on the same page about what email deliverability is, and why it is so important, let’s dive into some actionable steps to ensure your deliverability is as healthy as possible.

Build a healthy email list

The first step to achieving healthy email deliverability is to establish a healthy email list.

Sending emails to unengaged or low-quality contacts can quickly lead to increased unsubscribe rates, spam reports, and a damaged sender reputation.

So, to ensure a healthy list, focus on gathering organic, legitimate email addresses from recipients who have explicitly opted in to receive communications from your brand. Also consider implementing a double-opt-in process to further validate the authenticity of your subscribers.

And don’t forget to regularly manage and maintain the list by identifying and removing unengaged subscribers after attempting re-engagement campaigns.

Prioritise sender authentication

Sender authentication is crucial for building trust between senders and recipients.

It involves implementing protocols to verify the authenticity of your emails and prove they come from your domain, and not from spammers.

Two essential methods for sender authentication are SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail).

SPF defines authorised mail servers allowed to send emails on your domain’s behalf, whilst DKIM adds a digital signature to validate the integrity of your messages during transit.

By using these protocols, your emails have a better chance of bypassing spam filters and reaching recipients’ inboxes.

Monitor and maintain your sender reputation

Internet Service Providers (ISPs) and email providers implement processes to protect inboxes from spam and to ensure trustworthiness before delivering emails.

To ensure a healthy sender reputation, regularly clean your email list to reduce bounce rates caused by invalid or non-existent email addresses. And minimise complaints by sending relevant and targeted content to recipients through segmentation and personalisation tactics.

As previously mentioned in this guide, aim to avoid sudden spikes in email sending volume, as they also may raise red flags for ISPs.

Optimise your email content

Creating relevant and engaging email content is essential for encouraging recipients to interact with your emails, and reduce the risk of them being marked as spam.

To ensure your content is optimised, avoid using elements that trigger spam filters, such as excessive capital letters, exclamation marks, misleading subject lines, or specific words like “Free,” “No fees,” or “Congratulations.”

Again, segmentation and personalisation tactics can help deliver more relevant content to recipients, improving engagement metrics.

And don’t forget to consider mobile optimisation of your emails. 81% of emails are opened and read on mobile devices, so a mobile-friendly approach is more likely to ensure a positive user experience.

Analyse email performance and sender reputation

Last but not least, regularly monitor and analyse your email performance to understand exactly how well your emails are being received, and identify areas for improvement.

Be sure to keep track of key metrics such as open rates, click-through rates, bounce rates, and spam complaints. And, regularly monitor your sender reputation through tools like to gain insights into how mailbox providers view your domain.

Our recommended email deliverability tools

Email deliverability can be a complex and sometimes time-consuming element of email marketing. However, it is also crucial.

To help email marketers out, here are 5 areas of email deliverability that can be supported, and the tools to help.

Monitoring IP addresses is a popular free tool which will rate your IP address reputation based on factors such as spam complaints, email bounces, and spam traps.

Furthermore, it can also provide details on how specific mailbox providers view your IP address for added insight.

Verifying and cleaning lists

Everest by Validity offers a range of deliverability tools, with robust list validation.

Email lists can be verified to ensure they are accurate, identifying those that are fake, dead, or could be significantly detrimental to list health if sent to.

Email creation and development

Mailtrap provides a sandbox environment for the development stage of email creation, allowing users to inspect and debug their emails within staging, dev, and QA environments.

The platform also offers the ability to run automated tests on a range of scenarios, allowing users to practise a little more caution pre-send.

Testing and tracking

If you’re an email marketer, chances are you’ve heard of Litmus.

Litmus boasts industry-leading email testing and tracking capabilities, claiming that they can cut email testing and QA down by a whopping 50%.

Their functionality includes previews in popular email clients, automated QA tests, and spam testing. As well as the ability to review campaigns alongside their ESP or code editor with their Litmus Chrome Extension.

Spam testing

As well as being a comprehensive deliverability tool, GlockApps provides robust spam testing functionality.

Email marketers can identify exactly where in the inbox their emails are being delivered within all major email platforms. And gain further insight and actionable steps to improve their deliverability.

The platform also integrated with all major email service providers and email marketing tools, making it suitable for most businesses.

Critical and transactional emails

For those particularly critical emails, Postmark provides a platform that ensures marketers never lose a single communication. As well as ensuring emails arrive quickly to keep recipients up-to-date and reassured.

To add another layer of security, Postmark provides 45 days of full content history, recipient information, and message events so that businesses can fully dig into any deliverability issues or concerns.

Next steps

Is email deliverability essential for email marketers?


Is it simple?

Unfortunately, no.

But worry not, if you’re feeling a little overwhelmed by this integral element of email marketing, then we can help.

As a dedicated email marketing agency, our team of experts know everything about email deliverability. And can support you whether you are facing deliverability challenges, or simply want to keep your deliverability as healthy as possible.

Get in touch for a chat or to find out more about our email marketing deliverability services.

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