How To Improve Your Email Deliverability Rates

|by Demi Donohoe

Email is alive and thriving. The number of email users in 2023 is set to hit 4.3 billion across the globe, showing that email remains one of the most useful channels of marketing out there.

However, it doesn’t matter how valuable your emails are if no one sees them. Whether you’re sending creative HTML campaigns, notification emails, order confirmations, win-back emails, or automated campaigns, a message that never reaches the inbox is a total waste of resources. That’s why email marketing success starts with good deliverability rates.

To get the most out of your email marketing program, in this post we’ll be diving deeper into how you can boost your delivery rates.

What is email deliverability?

Email deliverability is a metric that represents how many emails successfully arrive in the recipient’s inbox without bouncing or being marked as spam. (Not to be confused with email delivery, which simply means that an email has been successfully delivered to the recipient’s server.)

You can easily work out the deliverability rate of your emails by dividing the number of emails that were delivered by the number of emails that were sent. It determines the number of contacts that received the email as a percentage of the total number of intended recipients, minus any hard or soft bounces.

Why is email deliverability important?

Chances are that you put a lot of time and effort into your email marketing campaigns. However, all that effort is wasted if the email never arrives in the inbox. For your campaigns to have their desired impact, they need to actually land in the recipient’s inbox.

Think about the important emails that your customers need to receive from you: password resets, delivery updates, order confirmations, and receipts. If these emails don’t arrive, you’ll lose trust, loyalty, and ultimately, you’ll lose sales.

With eye-catching designs and valuable content, your emails will surely arrive safely, right?

Not necessarily. Many factors play into email deliverability rates. These factors ultimately determine whether or not your emails are delivered successfully.

So, how do you make sure your campaigns reach your subscribers’ inboxes? Keep reading to find out.

Why is my email deliverability rate low?

Whether the deliverability rate for one of your campaigns is suffering or you have noticed a deterioration overall, you need to rectify the cause quickly. Building trust through your email campaigns forms the basis for success.

High deliverability rates often reflect good-quality email campaigns with high-quality content, an engaged email list, and good list hygiene practices.

Deliverability rates can deteriorate for a number of reasons and it can be hard to single out one individual cause. Let’s take a look at the main factors that might be affecting your email deliverability success.

Sender score

Like a credit score, a sender score is based on reputation. The higher your score, the better your reputation and the higher your deliverability rate.

Your sender score is calculated based on the reputation of your IP address. It’s used to compare the reputation of similar email accounts. If your deliverability rate is starting to decline, the sender score is a good starting point for examining the reasons why.

Achieving a perfect sender score is achievable if good sending practices are followed. The more a sender score deteriorates, the less likely it is that email campaigns will be delivered.

Factors impacting the sender score include:

  • The number of complaints - These are measured by the number of emails that you have sent that have been marked as spam manually.
  • The volume and frequency of sends - Consistency is key to a good sender score. If you are following best practice, such as segmenting your lists and sending relevant and timely communications, you should have a regular routine of sending and volume of emails being sent.
  • External reputation - Do your email contacts trust you? If they are engaging and interacting then the ISPs will also trust you. That increases the sender score and increases delivery rates.
  • Unknown users and unknown user rates - How often do you send to email addresses that don’t exist? This is a big measure of how efficient your data collection is how effective your list hygiene processes are. Although it can happen, there isn’t much of an excuse for sending to email addresses that don’t exist.
  • Accepted and rejected rates - How many of the emails that you send get into contacts inboxes? If a lot of them are soft bouncing, this is also a signal to the ISPs that all might not be above board. Do you need to change your copy so that it is less spammy? Are the emails that you are sending too large? Is there too much imagery in them and not enough text? These can all affect whether you get put into a spam folder or not.

You should keep an eye on the number of complaints that you receive. Although the volume of email sends doesn’t directly impact your sender score as a standalone factor, it’s taken into consideration when calculating the percentage of emails which have triggered a complaint.

A sender who distributes two thousand emails in a campaign and receives two complaints will have a higher sender score than one which only sends two hundred and receives the same number of complaints.

The good news is that if you have a low sender score, the scores are calculated on a rolling 30-day basis, so changes that you make will be quickly reflected.

Spam filters

Spam filters can cause your emails to be blocked before they reach the recipient’s main inbox. Spam filters look for certain traits in an email campaign that might indicate it’s spam. Here are the main causes of emails landing in the spam folder:

  • Copywriting - Content that’s irrelevant to the recipient runs the risk of being flagged as spam, which lowers your sender reputation. Sending high-quality, relevant content is much less likely to be considered as “spammy.” And by providing valuable content to your audience, your unsubscribe rate should stay low, which is another important factor.
  • Links - Any links in your email will be checked by the spam filter to ensure that they connect to legitimate websites and landing pages. Link spam, where an excessively high number of links connecting to the same URL are contained within the email copy, is forbidden.
  • Images - The text-to-image ratio of an email is also checked. Emails should contain a higher proportion of text than images (60% text and 40% image is around the lowest amount of text that you should include).
    Alt-text should be added to any images that you choose to include in the email. In cases where the image can’t be displayed for any number of reasons, your alt-text will show in its place. The alt-text should be descriptive enough so that the recipient’s reading experience is not impacted in a text-only format.

Ensuring that your emails are not marked as spam is imperative for long-term success. Although your deliverability rates may remain high in some cases, if your emails have previously been identified as spam it’s likely that your future sends will in end up in spam folders, too.

Firewalls and IP checks

Firewall and IP checks take a detailed view of the deeper aspects of an email which is sent out by a user. The firewalls and IP checks look for spam accounts, account histories, the domain that the email originates from and whether the user has the necessary permissions to send an email from that IP.

All of this information is found in the “envelope” of the email:

Screenshot of an email envelope

Firewalls exchange information between networks and computers to identify known spam accounts, sharing the knowledge that they gather over time. Known spam accounts will be blacklisted by internet service providers to ensure that none of their emails find their way into the inbox.

When an email passes through a firewall, the existing users that the email address has sent to is examined. A user who sends to a high volume of spam email accounts will likely fail a firewall check.

If a sender is responsible for sending a number of abusive emails to one particular recipient, they may choose to block that IP address to prevent any further correspondence.  Once an IP is blocked, it does not matter whether the sender sets up a new email account as none of the emails from that location will reach their intended recipient.

Email size

Be conscious of the size of your emails. Some email sends may suffer low deliverability rates if your email contains large attachments or high-resolution images or GIFs. Bulky emails take longer to load when they are delivered but are also more likely to trigger spam filters.  Although visually appealing emails may be more attractive to the human reader, a balanced approach needs to be taken.

Remember – 60% as a minimum for text content, 40% as a maximum for images.

To provide your email recipients with a seamless experience, include a link to a page where the reader can find out more. Another good alternative to large attachments is cloud storage. Cloud storage allows for the storage of files and document on a server. Provide the email recipient with the address of the file on the cloud and ensure that your file privacy settings allow the email recipient to use the file.

How to improve your email deliverability rates

Now you know the factors that might be getting in the way of your email deliverability, what are the things you can do to ensure your emails land safely in the inbox?

Avoid sudden changes to your email volume

If you want to significantly increase the number of emails that you send out on a regular basis, you should gradually increase emails over a period of time. Increasing your email volume suddenly and dramatically may slow down or even stop some of your emails from being delivered.

Plan email volumes on a calendar to map out any changes, gradually increasing your email volume. You can also use that calendar to analyse when your deliverability suffers and whether the number of email sends was a factor.

Warm-up your IP address

When using a new email address, slowly introduce the email sends to your contacts. Ensure that the first few contacts that you send emails to are reliable, will not mark your content as spam, and won’t unsubscribe from your communications.

Sending a large email campaign from a cold IP address is likely to cause problems with your deliverability. You should take caution with sending your emails until your reputation is established. Be alert and responsive to any patterns in your email analytics. If your emails don’t get delivered, take action before sending out larger campaigns.

Clean your list

Make sure that you’re only sending to contacts who actually want to receive your emails. Sending your emails to a list of engaged followers who open and engage with your email content will significantly improve your sender reputation. 

On the other hand, sending emails to disengaged contacts who ignore, delete, or worse – mark your emails as spam – will have a negative impact on your reputation. Removing known spam accounts, misspellings, and deactivated accounts from your email list will reduce your hard bounce rate and increase your sender reputation.

Segment your data

Segment your contact lists to ensure that you’re only sending the most relevant content to your subscribers. This is a good way to avoid spam complaints if you’re sending an email that is only relevant to a small number of your email subscribers. Reducing the number of spam complaints for your email will improve your sender score and help to build your reputation over time.

Look through your own spam folder

Look at your spam folder for examples of emails that have been recently detected by spam filters. Spot any new patterns including any phrases that regularly appear in the subject line or body text of these emails and avoid using them in your own campaign.

Always test your emails before sending

Conducting an email test gives you a good opportunity to see which parts of your email are effective and where improvements can be made. Although tests are primarily useful to check your content, you can also ensure that your emails and any images they contain, render correctly in the recipient’s inbox. You can use an email marketing tool like Wired Plus to carry out pre-campaign checks.


Improving your email deliverability rates takes time and patience. It’s a strategy that you’ll need to be constantly refining to deliver valuable emails to your audience. Ultimately, a clean, engaged contact list that leads to a strong sender reputation is the key to deliverability success. Keep an eye on your subscriber data and your email reports to ensure you’re targeting the right people with the right message.

By following these email deliverability tips and best practices, there’s nothing preventing you from reaching the inbox.

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With a full-featured email marketing platform that offers powerful list segmentation, flexible automation workflows, and actionable analytics, all of your marketing needs are met in one simple platform. To see it in action, book a free, no-obligation demo.

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