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The 5 principles of email deliverability

August 10 - 2023

Email Marketing Strategy 5 min read

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Did you know that email ROI is $36 for every $1 spent?

Or that 89% of marketers use email as the primary channel for generating leads?

Impressive, right?

Unfortunately, none of these statistics matter if your emails aren’t getting in the inbox.

The success of your email campaigns depends heavily on your email deliverability, in short, your emails landing in recipients’ inboxes without being blocked or filtered out as spam.

In this blog post, we'll explore the five fundamental principles of email deliverability, and provide practical tips to ensure your messages successfully land in inboxes.

Build a healthy email list

Prioritise sender authentication

Monitor and maintain your sender reputation

Optimise your email content

Analyse email performance

Next steps

Build a healthy email list

The very foundation of email deliverability begins with a healthy email list.

Because if a business is regularly sending to a list of low quality, unengaged contacts, this will quickly have an impact on unsubscribe rates, spam reports, and ultimately sender reputation.

A healthy list should be made up of recipients who have explicitly opted in to receive email communications from your brand. Or even better, have been through a double-opt-in process to ensure they are genuine.

Gathering organic, legitimate email addresses and data isn’t the only element of building a healthy email list. It also requires management and maintenance.

This means identifying those subscribers who are simply not engaging any more, and removing them from your list. This should be after a process of attempted re-engagement through relevant campaigns. But if your efforts fail, it’s simply time to say goodbye.

Prioritise sender authentication

Sender authentication refers to the process of showing email providers that mail servers have your permission to send emails on your behalf. 

This is an essential deliverability step for establishing trust between senders and recipients. And involves implementing various protocols that verify the authenticity of your emails, proving they genuinely come from your domain and are not forged by spammers.

Two key sender authentication methods are:

SPF (Sender Policy Framework)

SPF defines the authorised mail servers allowed to send emails on behalf of your domain. When your emails are sent, the recipient's server checks SPF records to verify your message's legitimacy.

DKIM (DomainKeys Identified Mail)

DKIM adds a digital signature to your outgoing emails, allowing the recipient's server to validate that the message's content hasn't been altered during transit.

Both SPF and DKIM authentication are essential to ensure your emails have a higher chance of bypassing spam filters and reaching the recipients’ inboxes.

Monitor and maintain your sender reputation

Email has come a long way since the days of spam, viruses, and salacious emails filling up inboxes. 

Today, Internet Service Providers (ISPs) and email providers implement processes to protect inboxes from such activity, and to ensure the sending domains of businesses boast a robust and established reputation before they trust you.

Essentially, every time you send an email campaign, ISPs will collect valuable data to identify whether you are following proper sending best practices.

There are two types of email reputation to be aware of:

Internet Protocol (IP) reputation

Emails come from IP addresses, which are unique identifiers of email streams.

Some businesses will send from a shared IP, which means multiple businesses use the same IP address to send email. 

Whereas, businesses with higher email sending volume usually choose to send from a dedicated IP address that belongs only to them. 

Domain reputation

Domain reputation focuses on your sending domain, meaning that your branded website takes priority when it comes to ISP filtering decisions.

Some email providers will focus more on your domain reputation instead of your IP reputation. However, many will look at both your IP and domain reputation when reviewing how trustworthy you are.

To maintain a positive sender reputation, both in terms of IP reputation and Domain reputation, we recommend several best practices:

Reduce bounce rates

Regularly clean your email list to remove invalid or non-existent email addresses (which could actually be spam traps), as high bounce rates will negatively impact your reputation.

Minimise complaints

Ensure that your content is as relevant and targeted to the individual recipient as possible. This ensures that they appreciate receiving your email, as opposed to being frustrated by its irrelevancy, and marking your communications as spam.

Maintain sending patterns

Avoid sudden spikes in email sending volume, as this can cause red flags for ISPs and may suggest you are ‘spamming’. Instead, try to maintain a regular and consistent sending schedule, ramping up activity gradually.

Monitor engagement metrics

ISPs favour businesses who send emails that recipients actively engage with. So, regularly monitor your open rates, click-through rates, and other relevant metrics to identify any engagement issues and address them proactively.

Optimise your email content

Creating relevant and engaging email content is crucial not only for encouraging recipients to interact with your emails, but to also ensure you avoid spam filters set up by ISPs. 

To improve email deliverability, consider the following content tips:

Avoid spam filter triggers

There are certain content elements that are more likely to trigger spam filters so should be avoided. These include excessive use of capital letters or exclamation marks, misleading subject lines, or certain words such as “Free”, “No fees”, or “Congratulations”.

Segmentation and personalisation

Ensure that you are segmenting and personalising your email campaigns to the individual as much as possible. This will result in more relevant content that the recipient will want to engage with; improving your engagement metrics.  

Mobile Optimisation

With 81% of emails being opened and read on mobile devices, it is integral your business takes a mobile-friendly (if not mobile-first) approach to email design. This ensures that recipients can easily engage with your communications, and won’t become frustrated with the user experience.

Analyse email performance

Once you have implemented all of the above, it is essential that you monitor and analyse your email performance on a regular, ongoing basis. This practice is crucial for understanding how well your emails are being received, and identifying areas for improvement before issues arise.

We would recommend monitoring the following metrics to keep track of your email performance and potential deliverability issues:

  • Open rates
  • Click through rates
  • Bounce rates
  • Spam complaints

In addition to tracking the above metrics, we recommend monitoring your sender reputation regularly. This can be achieved through tools such as, which offer insights into how mailbox providers view your domain, and will flag any potential issues.

Next steps

We understand that whilst email deliverability is important, it’s not always straightforward.

There’s a lot of jargon to wrap your heads around and technical elements to consider. And that’s before worrying about your email design and content.

If you’re feeling overwhelmed, then we can help.

Get in touch with our team of email experts to learn how we can improve your email deliverability, and maintain it long-term

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