12 Best Email Testing Tools to Increase Email Deliverability

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Written by:Aquibur Rahman


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Testing your emails is an essential part of any email marketing campaign. You want to make sure that the email looks right, has no errors, and gets the highest deliverability. As email testing is the best way to refine your email campaign strategy, you must test your emails. In this blog, we will check out in-depth about the best email testing tools available.

Table of contents

What is email testing?

Email testing enables pre-send and robust testing of your emails like link validation, inbox rendering previews, in-app spam testing, and more. It enables you to show a preview of how email can perform across different spam filters, devices, and inbox providers before sending.

Why should you test emails?

Performing email testing helps you spot common errors like how your subject line appears on different devices, if the font and HTML look fine, etc. The email that looked good in your inbox might not look the same to other recipients, and this is why you should test your emails over different email clients. A single mistake can make your business fail.

Also read: Why You Should Test Your Emails Before Sending Them

How is email testing done?

Before diving in-depth into the procedure, let's understand the basics of how email testing is done.

1. Content testing (Subject line, proofreading, etc.)

It deals with identifying the grammatical errors and sentence construction errors in your email copy.

Checking every link in the email copy ensures whether any hyperlinks you have provided to the web pages in the email are opening on every browser as intended.

3. Deliverability testing (for spam filters & domain reputation)

It can be done in two crucial steps, namely manual and automated email testing. But manual testing is complicated when your number of emails is high. The superior option that can be used to test emails at present is an automated testing service. In this case, you need not maintain any labs, and you can provide screenshots of different email displays. Testing services contain a spam risk assessment for finding email deliverability problems and correcting them. Various automated email testing tools can make your work easier.

What should you look for in a good email testing tool?

Following are some crucial aspects you need to look for in a good email testing tool.

1. Accessibility

Make sure that it is an online email verification tool that works as SaaS (Software-as-a-Service). These tools don't need computer resources as they are easily accessible anywhere and anytime from any device.

2. Scalability

The email testing tool you choose should be capable of testing an extensive email list. Bigger email lists take time in some cases but are mostly made instantly.

3. Product features

This is a crucial point to note. The email testing tool you pick should have a diverse feature-set that includes the capability of HTML validation, email preview, and subject line testing, and most importantly, deliverability issues.

4. Integrations

Make sure the email testing tool you pick integrates with different tools like email list management tools, email sending tools, email generation tools, and more.

Email testing tools and features

1. Content testing

a. HTML validation and Email Previewing tools:

Email previewing tools help you test how the email you are sending will look for your recipients in different devices, email clients, and browsers. HTML validation tools also perform the same, but the one option they focus on is to check the actual CSS code, XHTML, or HTML for errors.

Email on acid

Description & key features

Email on Acid is best suited for SMBs and enterprises. It achieves efficiency, protects brand reputation, delivers email perfection, and enhances marketing ROI. It has its capabilities, and it provides preview testing on more than 70 email clients and devices. SMBs will get the most benefits if you work as a part of a team on your newsletters.


They have a 7-day free trial, and the premium packages start at $73/month.


Description & key features

Litmus is the top email testing tool used by different businesses. The email preview feature of the tool is the main reason why you should go for this. When you set up a test email, the tool will automatically show how it will look in different formats and devices.


They offer a 7-day free trial, and the premium packages start at $99/month.

  • Litmus basic: $99/month

  • Litmus plus: $199/month

  • Litmus enterprise: customized

You can preview emails just with the basic version, but if you need to increase the platform's potential, you need to sign up for higher packages.

Description & key features is best suited for all marketing and development teams from SMBs, Midmarket, and enterprises. Mailtrap helps you isolate test emails and eliminates the risk of email landing in the recipient's spam folders. It works by integrating every SMTP server with a particular inbox of the Mail trap. Once it has reached the inbox, you can perform any HTML validation or render as per your preference.


They have freemium. Jump on it and give it a try. The premium packages start at $9.99/month.

  • Free – $0

  • Individual – $9.99/month

  • Team – $24.99/month

  • Business – $49.99/month

  • Premium – $99.99/month

  • Enterprise – $299.99/month

The free tier unlocks every feature, but you will not enjoy the exclusive benefits for a longer time. You need to choose a higher tier if you need to test more emails.

b. Subject line testing tools

Your open rate increases only based on what your subject line is. Here are three crucial subject line testing tools to help you achieve commendable open-rate metrics.


Description & key features

SubjectLine is one of the best to check the subject line for suggestions and spam markers to increase your open rates. The subject line testing tool looks at the collected data from different partners and then makes the determinations. It works in real-time and usually gives you line-based decisions. It's a free online tool that anybody can access.

Email subject line grader

Description & Key features

Email Subject Line Grader is another best and free subject line testing tool available. It will test your subject line type's effectiveness, the word mixture, word count, and your copy. Just copying and pasting the subject line into the action box is enough. You get unbiased feedback and also act as proof. It will look over the grammar and length of the subject, which is considered most important in mobile devices. It also considers the email subject line elements to make changes or add emoticons to the subject line.

Zurb subject line preview

Description & key features

Zurb subject line tool previews your text and subject of email on various mobile platforms. Most of the email subscribers check out emails on mobile devices. It means you need to make the emails mobile compatible too. The tool shows how your subject line will look on different mobile devices. You just need to check whether the subject lines and format look good on every device.

2. Deliverability testing tools

Deliverability issues can harm your email marketing campaigns. So it's always best to do occasional spot checks and be proactive.

a. Sender reputation deliverability tools

Sender Score

Description & key features

Return Path has developed a free tool called Sender Score, and it grades your IP address reputation on a scale of 0 to 100. It also includes a blocklist lookup tool that ensures whether your IP address is blacklisted. Some of the highlighting features of the sender score include the breakdown of your score, fast sender score scanning, and a powerful indication of your reputation.

It's a free tool.

Postmark spam check

Description & key features

One of the free tools that check whether there are any spam words in your email copy. It makes recommendations as well as grades your content. You can just copy and paste the email code to the UI interface. It checks diverse email variations for spam scores. It's the best tool for obtaining the score and enhancing your email.

Access the free tool here.

Reputation authority

Description & key features

It's one of the best tools used by marketers who need to check their IP reputation score or the domain. Watchguard, one of the top-notch online security technology companies, has developed this tool for free, and it is easy to use. You just need to enter the IP address or domain name in the given field. It offers the domain and related IP address matching the reputation with bad and good mail ratios originating from the specific domain.

b. Deliverability tools

Just verifying your sender reputation is not enough to make your emails land in the inbox. You need to use various deliverability tools that can be used to explore other issues. Here are some of the best deliverability tools you can use.


Description & key features

SendForensics is used by enterprise marketers. This is one of the best securities and email deliverability tools that protect marketers' email reputations. It enables marketers to test different emails for engagement and delivery. It can further be used to counterfeit DMARC compliance, emails, and test network deliverability.

Pricing (Offers free trial & freemium benefits)

They have a freemium, and the premium packages start at $39/month.


Description & Key features

GlockApps is used by different businesses to detect phishing, prevent spam complaints, identify malware, and more. The tool checks your authentication, reputation and offers detailed feedback for corporate filters and standard ISP. Primary spam filters scan your email and analyze the issue to enhance your ROI, open rates, and deliverability.


The premium package starts from $59 per month, and it does not have any free version, but it does come with a 14-day free trial.


Description & key features

MxToolBox provides lookup and monitoring solutions that make sure that you possess enabled DKIM (DomainKeys Identified Mail), SPF (sender Policy Framework), DMARC (Domain-based Message Authentication, Reporting, & Conformance). The tool helps offer complete data on the sender's IP reputation, people who are sending email from your domain, senders geolocation, alerts when there are any changes made in your email reputations, and more.


Free users only receive a free monitor for one month, whereas the paid users get multiple monitors, advanced email delivery tools, and more blacklists.

What's the right pick for you?

Picking the right email testing tool is essential to get started. Choose tools that provide you affordability, intuitiveness, and deliverability. Once you have picked the right email testing tool, you can use Mailmodo to send your email campaigns. With Mailmodo, you will be able to create and send actionable emails that power unique email experiences.

Sign up now

About the author

author profile avatar

CEO at Mailmodo

Aquibur is the CEO and co-founder of Mailmodo. He's helped various tech companies set up their email marketing infrastructure. His work has appeared in the Search Engine Journal and Martech Zone.

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