Email Testing for Beginners – Complete Guide

Wondering where to start with email tests? Not sure how to make your templates highly deliverable? No worries, I got you covered. 

This article guides you through email testing for beginners including definitions, types of testing, tools, and tips for best practices. 

What is email testing?

Email testing is running your email template through testing tools and applying specific methodologies (e.g. A/B testing) to serve two purposes: 

1. Catch errors before they reach your audience (use Mailtrap Email Testing).  
2. Gather insights for improving future email campaigns (use Mailtrap Email Sending or other tools)

The role of email testing explained

1. Error prevention: Popular email clients update frequently, leading to emails rendering incorrectly or not reaching the inbox. Even small errors, like a broken link, can significantly impact your campaign’s ROI. And it’s not uncommon for recipients to unsubscribe from an email just because it didn’t display or work well. Mind you – these errors will also affect your transactional emails, making it all the more important to send bug-free emails. 
2. Gathering insights: Beyond just checking for rendering issues, email testing allows you to conduct tests on elements like subject lines, providing valuable insights into what resonates best with your audience. This information is crucial for crafting more impactful emails. It helps improve email engagement which, in turn, improves your sender’s reputation and overall deliverability.

Types of email testing

Generally, I’d argue that there are three main types of email testing:

1. Sandbox tests
2. Pre-production tests
3. Production tests

Sandbox tests happen in an isolated environment, usually via a fake SMTP, and give you an accurate estimation of the following:

• How your email template performs against popular mailbox providers 
• If the template is going to trigger spam filters 
• If your IP or domain appears on a blacklist  

Pre-production tests can, for example, involve DNS authentication tests to ensure your SMTP server is properly authenticated. Or you can run server-side load testing to see how the SMTP handles the traffic. 

Note that I won’t go into the details of pre-production tests for two reasons. 

1. These aren’t for beginners as they require extensive knowledge of email infrastructure.
2. I already covered pre-production testing tools in the linked article ◀️. 

However, I’ll speak about the production tests which may include A/B testing of various email elements, multivariate tests, email heat maps, etc. 

What email components should be tested?

All email components should be tested, including:

• Email template (HTML/CSS)
• Headers 
• Subject 
• Body
• Links
• Spam score 

Now, I want to make the whole story more granular by providing basic testing categories. It’ll help you better understand the testing process and which component tests you should run first. Also, I’ll leave explicit references if something should be done in a sandbox or on production. 

Quality assurance tests

1. Spam testing (sandbox): This step is critical to prevent your emails from landing in spam folders. If email service providers mark your messages as spam, it can hurt the deliverability of your future emails.
2. Design testing (sandbox): This test checks the format and image rendering across different apps and devices.

3. HTML testing (sandbox): This test inspects the HTML and CSS support for your email template and it’s tied to design and content testing. You should clearly see which template element might be problematic and how to fix it, plus have an overall market support score. 

4. Link validating (sandbox): This involves testing every link in your email to ensure they point to the correct locations. It’s essential for the effectiveness of marketing and transactional emails. It helps avoid broken or incorrect links, which can harm your brand’s reputation and subscriber experience. Mailtrap allows you to do it in a sandbox. 

Variable tests

Be careful with multivariate and A/B testing as these are production tests. 

If you fail to tactfully change the variables, or if you change too many variables, the test may yield misleading results. 

The same could happen if you run multivariate and A/B testing at the same time. Simply, it could be hard to understand which variable impacted the email engagement rates the most. 

1. Multivariate testing (production): This type of testing involves testing several variable combinations simultaneously. But you shouldn’t tweak the email body content and copy. For example, you might want to try the following:

• Different email templates with the same messaging 
• Combine that with different send times 
• And mix in different recipient segmentation cohorts (by industry, location, etc.)

The goal is to find the best set of variables that align with your audience (or audiences) and their preferences. 

Pro tip: If you want to test different templates with the same messaging make sure to run a sandbox test on each template to ensure it’s highly deliverable. In case it’s not, this will affect the multivariate test results. 

2. A/B testing (production): This is a widely used strategy where you send one variation of your email to a part of your email list (within the same segmentation cohort by industry, location, etc) and a second variation to another group. Again, be careful how you group the recipients, and don’t change too many elements. 

The reactions (opens, clicks, conversions) of these groups determine the winning email variation. A/B testing is effective in identifying which version of the message increases key performance indicators (KPIs). 

Here are the elements to test:

• Subject line: Test different titles to see which one leads to higher open rates.
• Preheader: This is the text/copy pulled from the initial line of your email body and can be crucial for engagement, especially with mobile users.
• Email Copy: Experiment with different hooks, messaging, and tone.
• Images: For image-heavy emails, test file size and optimization, especially for mobile devices. Generally, the image-to-text ratio should be 20%-to-80% tops. 
• Call-to-Action (CTA): Different CTA button colors or text lines can significantly impact click-through rates.

3. Email heat maps (production): These tests map how recipients engage with your emails. They’ll show the scroll depth, which area recipients focus on, and whether interactive elements attract attention. You can use heat maps in combination with multivariate and A/B testing. Tools that include heatmaps are Mailchimp and ActiveCampaign. 

Email testing tools

I have the most experience with Mailtrap, so I’ll cover the tests you can run using our platform. However, if you’d like a more extensive list of testing tools, I’ve already blogged about it, so feel free to click on the linked article 🔼. 

Mailtrap Email Testing

Mailtrap Email Testing is a sandbox to inspect and debug emails in staging, dev, and QA environments before sending them to your recipients. The testing happens on a fake SMTP so there’s no risk of spamming users. 

With Mailtrap, you can do any of the sandbox tests I mentioned earlier. Here’s a quick list of all the features, and I’ll cover the details later in the article. 

• HTML/CSS check
• Spam score check
• Email preview  
• API for QA automation

You also get:

• Ready-to-use integrations in 20 + languages (Ruby, Python, Node.js, etc.)
• Multiple inboxes for different projects and stages
• User management
• SSO 

Try Mailtrap Email Testing

Mailtrap Email Sending

Mailtrap Email Sending gives you email infrastructure with high deliverability by design. And you can choose SMTP and API to send. But, since you’re a beginner I’d suggest SMTP. Mailtrap also provides all the DNS authentication records for you, so you won’t need any external tools to run pre-production tests to check the records. 

Okay, but what does email sending have to do with testing?

To begin with, you cannot test deliverability without sending emails to real recipients. And, there are specific production tests you can do, and they’re all about understanding the deliverability metrics (delivery, opens, clicks, spam, etc). 

Also, Mailtrap allows you to set email categories to determine which type of email performs best with your audience. It also helps better manage your email campaigns. Plus, you can use Mailtrap email categories for A/B testing. 

More importantly, you get actionable in-depth analytics that helps quickly troubleshoot unexpected issues. There’s a helicopter-view dashboard with all critical metrics in one place. And you get drill-down reports for each email category and major mailbox providers. 

How to test your first emails?

Note that the following guidelines assume that you already set up Mailtrap Email Testing and Email Sending. If not, click the links to get started with each product. 

This how-to covers tests in order of importance, providing tips on the steps to take. 

Deliverability

Deliverability indicates the likelihood of your emails reaching the recipient inbox, not the spam folder. You can run a deliverability test in two stages – first in a sandbox and then on production to a limited number of recipients. 

• Sandbox (Mailtrap) – Select My Inbox under Email Testing, Inboxes tab. Choose your preferred technology under the Integrations drop-down. 

Make sure to customize the code using your email template and body with associated styles. Run the code, (e.g. you can simply run it in Terminal on MacOS) and your email will appear in the inbox almost instantly. Then, inspect the Spam Analysis and HTML Check tabs. 

• Production – If everything looks okay on the sandbox, choose ~100 recipients (preferably on different mailbox providers), send the email to them, and then inspect Stats to see deliverability data (you’re aiming for 90%+ delivered emails). Also, you may want to set a separate email category for production email tests; ◀️ click the link to see how to do it. 

Tip: If you want to check more email deliverability testing tools, click the link ◀️. 

HTML Checker

Mailtrap’s HTML Check gives you a clear and detailed overview of your email template and whether it’s supported by the most popular mailbox providers. Plus, you can see the support across the Web, Desktop, and Mobile devices. 

Better yet, you get the list of all the analyzed elements and the support, or lack thereof, for each element. And if something needs fixing, you’re only a click away from the specific line of code that could be problematic. 

Dive deeper into the world of email testing by checking out the full article at Mailtrap's blog. Your journey to flawless email campaigns begins here!