The Mega List of Best Email Testing Tools

On January 18, 2024
12min read
Veljko Ristić Content Manager @ Mailtrap

Testing 21 different apps to determine the best email testing tools took more than two months. But now, you get the ultimate list to check your campaigns inside and out. 

I designed the list to feature email testing software that’s helpful for dev/QA, and marketing teams. To that, most of the apps covered are for qualitative tests (how good and deliverable your emails are). But, towards the end, you’ll also find three pro tools for quantitative tests (load and stress testing) on SMTP servers. 

Disclaimer: This article lists prices, specific features, and software catalog scores. These were available and valid at the time of writing but could be subject to change by the time you’re reading the article. 

Email preview and spam testing tools

An email preview shows what an email looks like on different devices, browsers, or popular email clients. By extension, spam testing tools, do exactly what their name suggests – give you an accurate estimation whether different email clients would see your email as spam. 

Below are the top three apps that feature both functionalities. 

ToolFree trialPricing fromKey features
Mailtrap Email TestingAvailable$14.99/month-Fake SMTP Server
-HTML/CSS check
-Spam score check -Testing API
-QA automation
-Email previews 
LitmusAvailable$79/month-Spam testing, -Litmus builder, -Advanced security, -Integrations with marketing tools.
Email on AcidAvailable$74/month (annual billing)-HTML testing
-URL validation -Image validation -B2B/B2C spam filter testing
-Heat mapping

Mailtrap Email Testing

Free trial: available

Pricing from: $14.99/month 

Captera: 4.9 ⭐ G2: 4.8 ⭐

Mailtrap Spam Analysis

Mailtrap Email Testing is part of Mailtrap Email Delivery Platform (which also features email sending). It’s an email sandbox to inspect and debug emails in staging, dev, and QA environments before sending them to recipients.

Simply, the tool represents a safe environment to check and preview your emails, see their spam score, and check HTML/CSS. Mailtrap Email Testing also shows the level of support for your emails across different clients – web and mobile devices (iOS and Android). 

Indeed, it’s an automation-friendly testing solution to test emails in staging and prevent sending test emails to your customers by mistake.  



Free trial: available

Pricing from: $79/month 

Captera: 4.6 ⭐ G2: 4.6 ⭐

Source: G2 Litmus official image

Litmus allows your email to be previewed across 90 apps and devices. These include desktop clients like Outlook and Apple Mail, Yahoo, multiple mobile apps, and the most widespread web clients. 

Along with email preview, there are deliverability tools like spam testing, email analytics, and more. 


  • Spam testing
  • Litmus builder
  • Advanced Security
  • Integrations with famous marketing tools
  • Putsmail by Litmus (HTML email testing) 

Email on Acid

Free trial: available

Pricing from: $74/month (billed annually)

Captera: 4.4 ⭐ G2: 4.5 ⭐

Source: G2 Email on Acid official image

Email on Acid provides a long list of mobile, web, and desktop clients to preview your HTML email. Also, EoA will verify every link in your email and assist in finding the best code solutions in the test result window.

Lastly, I need to complement their email template editor, which is intuitive and a breeze to use. And it could markedly speed up your workflow even if you have little experience. 


  • HTML validation and testing
  • URL validation
  • Image validation
  • B2B/B2C spam filter testing 
  • Heat mapping
  • Maketing tools integrations

Test email deliverability

Just a side note: delivery indicates whether the recipients’ server accepted your email or not. Whereas, deliverability indicates if your email hit the inbox (not the spam). 

If you want to learn more, check our video ⬇️

Below, you’ll find the top three tools to prevent deliverability issues. 

Tool Free trialPricing fromKey features
BrevoAvailable$25/month-Marketing automation
-“Preview my email”
-Signup forms
-Email heat map
-A/B testing
MailgunAvailable$35/month-Email parsing -Transactional emails -Email authentication
-Burst sending
SendForensicsAvailable$39/month (annual)-Deliverability Analysis
-Reputation Dashboard-DMARC Monitoring -Blacklist Checker, 

Brevo (formerly Sendingblue)

Free trial: available

Pricing: from $25/month

Captera: 4.5 ⭐ G2: 4.5 ⭐

Source: G2 Brevo official image

Brevo is a full-on CRM platform that can send both transactional emails and email campaigns. You can also send SMS, track conversions, sales, and more. Sure, you can test deliverability, and some of the tests you may find most useful include:

  1. Preview the email marketing campaign with email clients
  2. Preview the emails acting as a particular customer
  3. Deliverability tests. 

Note: The listed pricing is for Brevo’s Marketing Platform product, at the time of writing. There are three additional products/functionalities, two of which are billed separately. 


  • Marketing automation
  • “Preview my email”
  • Signup forms
  • Email heat map
  • A/B testing


Free trial: available

Pricing: from $35/month

Captera: 4.3 ⭐ G2: 4.3 ⭐

Source: G2 Mailgun official image

Mailgun provides a decent mail deliverability test and offers a few solutions to improve the deliverability rate and sender score. You get deliverability services, email validation, email headers testing, and more. 

You can also opt for managed deliverability services. They provide customized strategy, custom reverse DNS, dedicated IP subnets, and so on. But note that this is close to an “enterprise plan” type of service. 


  • Email parsing
  • Transactional emails
  • Email validation
  • Burst sending (email marketing software) 


Free trial: available

Pricing: from $39/month [annual billing]

Captera: 4.3 ⭐ G2: 3.8 ⭐

Source: SendForensics landing page

SendForensics provides both pre-send and post-send optimization activities. It tailors a predictive model of how an email will reach recipients. SendForensics gives you the features such as email client preview testing, blacklist monitoring, content analysis, etc. 


  • Deliverability analysis
  • Reputation Dashboard
  • Spam checker 
  • DMARC analytics  
  • Blacklist Checker

Important Note:

Mailtrap Email Testing has deliverability testing features and you can use it as a deliverability tool, but for the sake of no repetitions (tooting our own horn too much 🙂) I didn’t include it here. However, you can read all about it in our blog post The Best Email Deliverability Testing Tools

Email verification tools

In the email verification space, three tools run the game. I tested a bunch of them, and still, the ones listed here are the fastest and most reliable. 

But, keep in mind that if you need to bulk-verify email addresses, the basic or free plan won’t cut it. And you shouldn’t skimp on the paid plans anyway. 

The reasons..?

Imagine you need to send to 10K+ addresses, and a percentage of those is inactive, non-existent, or spam trap. Without verifying the addresses before sending out the campaign, you’ll be dealing with a bunch of hard bounces and spam reports that will affect your domain and sender reputation. 

Here’s a quick rundown of the top three email verification tools.

ToolFree trialPricing fromKey features
ZeroBounceAvailable$15/2,000 email addresses– Email scoring- Email deliverability testing- Blacklist checking and monitoring- Email finder
NeverBounceNo$0.008 per email/pay-as-you-go model– Mail server validation- Domain health check-Automated list cleaning 
MyEmailVerifierAvailable (100 credits)$29 for 5000 credits– Real-time verification through API- High-risk email detection- Syntax verifier- Detectors: temporary unavailability, catch-all, rola account- Email list cleaning 


Free trial: available

Pricing from: $15/2,000 email addresses

Captera: 4.8 ⭐ G2: 4.6 ⭐

Source: G2 ZeroBounce official image

The go-to email optimization platform for Netflix, Amazon, and Disney, ZeroBounce offers 99% accurate email validation. The software detects invalid contacts and also abuse, disposable, spam trap, and catch-all emails. 

Checking 100,000 emails takes around 45 minutes. And, if you want to block poor-quality subscribers before they sign up, ZeroBounce provides a real-time API. 


  • Email scoring
  • Email deliverability testing
  • Blacklist checking and monitoring
  • Email finder


Free trial: not available

Pricing from:  $0.008 per email/pay-as-you-go model

Captera: 4.4 ⭐ G2: 4.4 ⭐

Source: G2 NeverBounce official image

According to their site, NeverBounce is used by Uber, Dell, and Doordash. The service is speedy,  ~45 minutes for 100K email addresses and less than 10 minutes for 10K. 

You can connect NeverBounce to almost 90 famous tools like Salesforce or SendGrid. 


  • Flexible pricing options
  • Mail server validation
  • Domain health check
  • Automated list cleaning 


Free trial: available [100 email credits]

Pricing from: $29 for 5000 credits 

Captera: 4.7 ⭐ G2: 4.7 ⭐

Source: YouTube MyEmailVerifier official channel

At the time of this writing, MyEmailVerifier was running a couple of discount programs. Overall, it offers a good balance of pricing and provided features. 

The service is fast offering a turnaround time of about 45 minutes to validate 100K email addresses. 


  • Real-time verification through API
  • High-risk email detection
  • Syntax verifier
  • Detectors: Temporary Unavailability, Catch-all, Rola Account
  • Email list cleaning 

Side Tip: Mail-Tester is a very good tool that didn’t make the cut for this list, but feel free to check it out. 

A/B testing tools

Email A/B testing denotes that a small number of total recipients get two different variations (A and B) of the email campaign. Typically, the variation with the highest primary email inbox placement and open and click-through rates goes to production.

Tool Free trialPricing fromKey features
ActiveCampaignNo$29/month for one user [paid yearly]– Up to 5 tests- Dynamic content- Subscription forms- Email segmentation

Campaign MonitorAvailable (limited)$11/month for 100 contacts– Various templates- Visual journey designer- Sign-up forms- Vast analytical capabilities
MailchimpAvailable$6.50/month -Custom-coded templates-Comparative reporting-Integrations with 200+ Apps-24/7 Email & Chat Support


Free trial: not available

Pricing: from $29/month for one user [paid yearly]

Captera: 4.6 ⭐ G2: 4.5 ⭐

Source: G2 ActiveCampaign official image

ActiveCampaign doesn’t provide A/B testing, but rather A/B/C/D/E testing, which is awesome! And of course, the way the tool visualizes the results is enjoyable and informative. Plus, their email design dashboard is a highlight indeed. 

I actually tested ActiveCampaign inside and out, and it’s definitely the best tool to run A/B tests. If you want more details, check this blog post


  • Up to 5 tests
  • Dynamic content
  • Subscription forms
  • Email segmentation 

Campaign Monitor 

Free trial: you can set up an account and create a campaign for free. But you need at least a basic plan to send the campaign to more than 5 recipients. 

Pricing: from $11/month for a list of 100 contacts

Captera: 4.5 ⭐ G2: 4.1 ⭐

Source: G2 Campaign Monitor official image

What you might find useful is Campaign Monitor’s results monitor. It is a graph that shows you how your campaign is doing. 

Results are defined according to the chosen performance metric: open rate, total unique clicks, or total clicks. Also, you can manually pick the winning email if necessary.


  • Various templates.
  • Visual journey designer
  • Sign-up forms
  • Vast analytical capabilities


Free trial: available

Pricing: from $6.50/month for 12 months

Captera: 4.5 ⭐ G2: 4.3 ⭐

Source: Mailchimp Help Center

Email A/B testing with Mailchimp works like this. 

  1. Pick the audience you want to send your campaign to. 
  2. Choose elements to test: subject line, content, and send time. You can use up to 3 variations of elements under testing. 
  3. Specify the percentage of recipients and criteria to determine a winner. (The criteria typically include click rate, open rate, total revenue, etc.) 

Then, you just need to set up the campaign and run it. The ease of formatting and deploying an A/B test is a stand-out with Mailchimp.  


  • Custom-coded templates
  • Comparative reporting
  • Integrations with 200+ Apps
  • 24/7 Email & Chat Support

Subject line tester

Some of the tools we previously covered offer subject-line testing. But if you’re looking for a separate piece of software, these are the free email testing tools to consider. 

Yes, they’re all free but remember that they only test subjects. 

ToolFree trialPricing fromKey features
Send Check ItAvailable Free tool– Simple subject line testing- Embedded API- HoppyCopy – a paid AI writing tool (free trial available)
Subject LineAvailableFree tool– Subject line testing
Email Subject line graderAvailableFree tool– Subject line testing- Scoring and suggestions- Character and word count

Send Check It

Free trial: available 

Pricing: free tool 

Captera: n/a ⭐ G2: 3.5 ⭐

Source: Send Check It results page

Send Check It provides a Slack Subject Line Tester and API. You’re unlikely to need anything else. 

The only thing I don’t like about Send Check It is the way results are presented. Based on the color coding, descriptions, and layout, you can’t tell if the subject line is good or not right away. So, if you use this tool, I’d suggest focusing on the first result only. 


  • Simple subject line testing
  • Embedded API
  • HoppyCopy – a paid AI writing tool (free trial available)

Subject Line

Free trial: available

Pricing: free tool

Captera: n/a ⭐ G2: n/a ⭐

Source: Subject Line results page

Subject Line works fast and gives exactly what you need to understand whether your subject line is a go or no go. Just paste your text in the field and hit Evaluate. Your target score is 100.

And despite the screaming red (check screenshots), you’re very clear on the results, unlike with Send Check It. 


  • Subject line testing

Email Subject Line Grader

Free trial: available

Pricing: free tool

Captera: 4.0 ⭐ G2: n/a ⭐

Note: The Captera score here is for the entire Net Atlantic, not just the line grader. 

Source: Email Subject Line Grader results page

This checker by Net Atlantic is also no frills. Email Subject Line Grader not only sets a grade to your subject line but also explains what’s wrong with it. 

Nonetheless, the tips seem a bit outdated, particularly if you account for all the email providers’ updates to marketing emails. Though, this doesn’t mean they’re wrong or misleading. 


  • Subject line testing
  • Scoring and suggestions
  • Character and word count 

Inbox placement tools

Inbox placement tools are there to help you ensure your emails reach the primary inbox at most ESPs and avoid the junk or spam folders. Here are some common features to look for:

  • Spam testing 
  • Sender reputation monitoring 
  • Testing email content against various spam filters
  • Reports on where emails are landing (inbox, spam, promotions tab, etc.)
Tool Free trial Pricing fromKey features
AllegrowAvailable Upon request– Email monitoring – Real B2B email addresses – DKIM, SPF, DMARC report monitoring- A/B testing email content- Spam score tracking
Validity (Everest)No$20/month– Inbox placement metrics from third-party data- Email problem areas diagnosis – Sender benchmarks – Sender Reputation Certificate program
KickboxAvailable $5 for 500 verifications– Inbox placement tests (seed email list)- Blocklist Monitoring- Reputation Monitoring- DMARC/BIMI Precheck


Free trial: available (Audit plan)

Pricing: upon request 

Captera: n/a ⭐ G2: 4.8 ⭐

Source: Allegrow homepage

Allegrow is among the leading solutions that help you reach your primary inbox. In my experience, it’s particularly effective for cold email deliverability. 


The tool is designed to be proactive, offering a unified email testing platform to secure, recover, and monitor inbox placement. Plus, it integrates directly into your work environment, with a focus on preventing landing in spam, promotions, or unfocused folders. 


  • Email monitoring 
  • Compatibility with sales platforms and tech stacks (e.g., SalesLoft, Salesforce)
  • Real B2B email addresses for sender reputation improvement
  • DKIM, SPF, DMARC report monitoring
  • A/B testing for email content
  • Spam score tracking and domain reputation insights

Validity (Everest)

Free trial: no 

Pricing: from $20/month

Captera: 5.0 ⭐ G2: 4.2 ⭐

Source: G2 Everest official image

Everest detects and solves deliverability threats and protects against blocklists and spam traps. It offers inbox placement insights, sender reputation, and infrastructure monitoring, integrated list validation, design tests, and subject line previewers. 

But what stands out for me, is the detailed analytics and reporting. The tool provides competitive intelligence, engagement metrics, real-time deliverability monitoring, alerts, and dashboards. Also, you get integrations with a bunch of email marketing tools. 


  • Inbox placement metrics from third-party data
  • Email problem areas – diagnosis and prioritization
  • Sender benchmarks of performance metrics comparison 
  • Sender Reputation Certificate program


Free trial: available

Pricing: from $5 for 500 verifications

Captera: 4.9 ⭐ G2: 4.2 ⭐

Source: G2 Kickbox official image

Kickbox’s UI is really good and clearly shows the percentage of emails that land in the Primary inbox, as well as Promotions and Social inboxes. 

For me, the strongest suit is the ease of integration. Even if you have little experience, it won’t take long to upload Kickbox’s seed list and start testing. Plus, the integration with popular email marketing tools (e.g. Mailchimp) is straightforward. 


  • Inbox placement tests (seed email list)
  • Blocklist Monitoring
  • Reputation Monitoring
  • DMARC/BIMI Precheck

SMTP test tools

SMTP test tools are for quantitative testing. Load and stress testing in particular. Thus, you verify whether the SMTP server works properly under any circumstances. 

The load testing measures the performance and functional behaviour of your SMTP server, under different types of load. You could test SOAP/REST, TCP, FTP, and more. And there are options to simulate a heavy load on multiple severs at a specific email throughput. 

The key benefit is understanding the SMTP server performance and how it may affect your deliverability. 

These types of tests are particularly useful for high-volume senders who rely on stable and predictable server performance. 

Tool Free trialPricing fromKey features
WormlyAvailable $44/month– HTTPS secured web server testing- POP3 mail server testing- Remote ping
GMassAvailable$19.95/month– GMass Chrome extension- Email analyzer- Inbox placement- Link checker
Apache JMeterAvailable Free open-source tool – SMTP server stress test- TCP- FTP- SOAP/REST- Webservices testing


Free trial: available

Pricing: from $44/month

Captera: n/a ⭐ G2: 3.5 ⭐

Source: Wormly homepage

Generally, Wormly is a solution for server, website, and uptime monitoring. You can use it to test your SMTP server easily as well. As indicated earlier, the tool sends a test email directly to your mail server for troubleshooting. 

Along with email server testing Wormly offers other diagnostic tools in a free plan including POP3 mail test, FTP server testing, etc. For those with higher-level needs, several paid subscription plans are available.


  • HTTPS secured web server testing
  • POP3 mail server testing
  • Remote ping


Free trial: available

Pricing: from $19.95/month

Captera: 4.8 ⭐ G2: 4.8 ⭐

Source: GMass landing page

This is a Gmail-centered service for email marketing campaign testing. Their SMTP Test Tool lets you check your connection to any SMTP server including popular email service providers like Sendgrid and Mailgun. 

Also, GMass offers a bunch of useful features for email marketing automation and testing. These include automatic follow-up emails, behavior-based campaigns, email list builder, etc.


  • GMass Chrome extension
  • Email analyzer
  • Inbox placement
  • Link checker

Apache JMeter

Free trial: available

Pricing: free open-source tool 

Captera: 4.5 ⭐ G2: 4.3 ⭐

Source: ApacheJMeter in-app screenshot

Apache JMeter is one of the oldest and most reliable Java apps to load test server performance and functional behaviour. And it’s one of the few tools that allows you to simulate a heavy server load for free. 

Of course, JMeter is primarily designed for engineers, devs, and QAs. But it has straightforward UI and flows, and the app is well-documented. So it’s possible for a tech-savvy marketer (like myself) to get the hang of it without too much trial and error. 

Also, don’t let the relatively low score across software catalogs mislead you. JMeter is truly out there with the best paid tools. 


  • SMTP server stress test
  • TCP
  • FTP
  • Webservices testing

Happy test fest

When all is said and done, I’d like to give you one last tip on how to choose among the best email testing tools. Consider how many campaigns you send and at what volume. Then choose one tool that offers a lot of testing options under one hood and allows you to automate testing flows. 

Then, if you send at a volume, Apache JMeter is certainly my recommendation for the server tests. And you can consider a dedicated IP address as well. 


Article by Veljko Ristić Content Manager @ Mailtrap

Linguist by trade, digital marketer at heart, I’m a Content Manager who’s been in the online space for 10+ years. From ads to e-books, I’ve covered it all as a writer, editor, project manager, and everything in between. Now, my passion is with email infrastructure with a strong focus on technical content and the cutting-edge in programming logic and flows. But I still like spreading my gospels while blogging purely about marketing.