Man sending an email.

Purpose and benefits of email testing tools

Marketers must ensure that their emails not only reach their intended recipients but also resonate with them. This is where an email testing tool comes in, as it gives you a space to refine and optimise your email campaigns, making sure that your emails arrive in your audience's inbox exactly as you designed them to. 

In this blog post, we delve into the purpose and benefits of using an email testing tool, as well as picking out some of the best email testing tools currently available.

Person sending an email.

The purpose of email testing tools

An email testing tool is a platform that allows you to see how your email looks on multiple devices and email clients before you send it to your audience. These tools allow you to simulate how your email will be displayed in a safe testing environment, giving you the chance to check for any spelling and grammar mistakes, as well as any issues with layout and images. They also offer valuable insights into your spam score, loading times, and link functionality, which helps you to improve your email deliverability and engagement rates.

According to recent data, worldwide, the number of emails sent and received per day in 2024 is 361.6 billion. This is a 4.1% increase from 2023 when the number of emails sent and received per day registered at 347.3 billion. In 2025 this figure is expected to increase to 376.4 billion emails per day. So, with that many emails going out every day, it has never been more important to make sure that your email stands out and displays correctly in people's inboxes.


Benefits of using email testing tools

Compatibility across email clients and devices:

With there being so many devices, email clients, operating systems and browsers available, making sure that your emails show consistently across them all is not an easy task. Email testing tools allow you to preview emails across different environments, making adjustments as necessary to avoid broken layouts, images not displaying correctly, unreadable text and other display issues. This is one of the most important features, so ensure that the tool that you use allows you to see as many different previews as possible. Remember, just because an email displays as intended on your browser, device and email client, that does not necessarily mean it will display correctly across all others.

Spam Filter

Avoid spam filters

Your brilliantly crafted email means little if it ends up in the spam folder. Some email testing software can analyse your email’s content and sending reputation, offering recommendations to improve your chances of landing in the inbox. Avoiding spam filters is key to getting good open rates and engagement rates, so choosing an email testing tool with spam testing functionality is important.

Laptop showing email metrics.

Enhanced engagement

Ensuring your email looks and works as intended on all devices, increases your chances of engaging with your audience. Some tools will also offer useful features like subject line testing and link verification, which can significantly boost your open rates and click-through rates. If you want your audience to engage with your emails, they need to look good and work as you intended, so selecting a tool with these features can help you improve your key email metrics.

Time and Cost Efficiency.

Time and cost efficiency

Identifying and fixing issues before sending can save you from costly mistakes. Rather than running multiple live tests, these tools offer a streamlined approach to troubleshooting, saving both time and resources. Email testing tools also offer great real-time collaboration features, allowing teams to work together seamlessly on email campaigns, further enhancing efficiency and saving time.

Person sending an email on a laptop.

Protect your sender reputation and brand

By rigorously testing your emails before sending them, you can avoid mistakes that could potentially damage your reputation. Spelling mistakes, incorrect images, layout issues and other errors can make your audience lose trust in your brand. It can look unprofessional and sloppy if emails are being sent out to customers with glaring issues, which can in turn hurt your brand reputation and make your audience lose trust.

According to a study conducted by Litmus, the return on investment (ROI) of email marketing, is that for every $1 you spend on email marketing, you receive $36 in return. So, make sure you invest in your emails, test them thoroughly and watch your ROI increase. Check out the full study here for further insights.


Recommended email testing tools

As an agency that is involved in email marketing projects, we know the importance of having a reliable email testing tool that does everything you need it to. Of all the testing tools we have used, Litmus and Email on Acid (EOA) stand out as the two best email testing tools currently available.

Litmus offers a comprehensive suite of email marketing solutions, including pre-send testing, analytics, and advanced segmentation, to help send better emails faster. Litmus has great integration functionality, allowing you to connect it with lots of different email service providers, as well as a handy Google Chrome extension, they also integrate with Slack, Google Drive, Dropbox and OneDrive. Litmus lets you preview over 100 different email clients and devices, with very quick rendering times, so you can see your previews in a matter of seconds.

EOA provides a robust platform for email testing to help make your emails look flawless on every screen. You can preview over 100 of the most popular email clients and devices, with unlimited testing and previews available. One of EOA's strongest features is its collaboration functionality, allowing teams to access and work on projects and comment in real-time. These features help to streamline the pre-send phase of an email campaign, improving efficiency and helping to increase ROI.

Both platforms have been instrumental in elevating the email marketing game, providing insights and capabilities that allow marketers to achieve their best results. However, it’s important to note that the two platforms do not have the same set of features, so you will need to consider what your needs are and compare their feature sets. Both platforms are also generally considered to be a bit expensive, so make sure you consider your budget. However, they both offer a range of plans for different size organisations, including custom enterprise plans.

To view a full breakdown of how the two platforms compare to each other, click here for Litmus and click here for Email on Acid.

Tip: To find out which platform is best for you, make sure you take full advantage of the free trials offered by the different testing platforms. This way you can get hands-on and work out for yourself which platform best suits your needs.

In summary

The role of email testing tools is critical to producing a successful email campaign. Although using an email testing platform will add additional costs to your campaign budget, what they provide and enable you to do, should make the costs more than worth it. Not only do they ensure that your emails look great and perform well across all email clients, but they also offer deeper insights into how you can optimise your campaigns for maximum impact. With tools like Litmus and Email on Acid, you will be better equipped than ever to craft compelling, engaging, and effective email marketing campaigns.


We hope this has helped explain the importance of using an email testing tool in your campaigns. If you need any further help, just get in touch!

Email Marketing Case Study.

Harley-Davidson: Leveraging email marketing to deliver exceptional ROI and eCommerce success

For our client, Harley-Davidson, we build and send out weekly marketing emails to help boost their eCommerce sales across Europe. For this we build the emails in Salesforce Marketing Cloud and then test all emails with Email On Acid, to check content and test for any email deliverability issues. For this campaign, the emails are sent out across 13 markets, in 6 languages, so thorough testing is critical to the success of the campaign. With this approach, the client has seen a significant increase of 831% ROI and a 154% increase in email-attributed revenue.

Read the full case study here.

Frequently asked questions

What are the key features to look for in an email testing tool?

The key features to look for are previews of as many clients and devices as possible, spam testing, link and image validation, as well as good collaboration features. Some other useful features to look for would be load time analysis, an easy-to-use interface, good customer support and integration capabilities.

Is there a limit to how many emails I can test?

This will depend on which tool you use and which plan you are on. On a free plan or free trial, typically there will be a limit on how many emails you can test, whereas most paid plans will be unlimited. For example, Email on Acid’s paid plans offers unlimited testing.

How does spam testing work?

Avoiding spam filters is crucial for email deliverability. A lot of these tools will have spam analysis features and will check for anything that might raise a red flag. They do this by assessing your email content for elements that might trigger spam filters, such as excessive capitalisation, suspicious keywords, or certain formatting issues.

What is an email preview?

Typically, an email preview is a screenshot from a live client, allowing you to see exactly what your subscribers see. Most tools will offer a range of different devices, browsers, operating systems and email clients. For example, both Litmus and EOA offer 90+ different previews.

Is there a free email testing tool available?

Some tools will offer a completely free plan. However, these free plans will come with very reduced features and a maximum amount of test emails that you can run. These are great to see if the platform will be well suited to you or if you have a very limited budget and don't need to do much testing.