For me, looking at all those options, some free testers and some paid ones, was quite overwhelming. Yet, I was determined to find a solution that would help me capture recipients’ attention and encourage them to open my email campaign messages. 

In this article, I will run through my top subject line tester picks as well as the pros, cons, pricing, and other details related to each one!

Quick summary of the best email subject line testers

Omnisend – Best for novice and established marketers looking for a solid tool with great popularity. 

Subject Line Tester Send Check It – Best for marketers looking for an intuitive tool to optimize their email subject lines. 

Headline Analyzer by CoSchedule – Best for beginner content marketers, bloggers, email marketers, and other creatives aiming to craft compelling headlines. 

Mailmeteor – Best for individuals and professionals keen on grading their email subject line ideas and generating new ones. 

Email Subject Line Grader – Best for users valuing simplicity in email optimization tools.

Subject Line Tester by Email Tool Tester – Best for realistic visual previews on mobile.

Comparison criteria to keep in mind

Before diving into the comparison criteria I recommend using to see how the tools stack up against each other, I need to share some honest insight… Email subject line tester tools are all quite similar in terms of looks, features, and overall offerings. So, if you’re looking for something game-changing, you might be in for a bit of a disappointment!

To let you see things for yourself and judge if my insights are correct, below, I provide you with two tables – one highlighting the similarities and one highlighting the differences between my top 5 subject line testers.

Similarities:

Differences:

Now back to the criteria:

• Level of expertise and project size suitability: Evaluate whether the tool is appropriate for your level of expertise and the scale of your email marketing operation. 

• Simplicity vs. comprehensive analysis: Decide if you prefer a streamlined, easy-to-use tool that provides quick feedback or a more detailed analytical tool that offers in-depth insights into your email marketing strategies.

• Feedback and recommendations: Opt for tools that not only analyze your subject lines but also provide enough actionable feedback and recommendations. 

• Integration capabilities: Consider the tool’s ability to integrate with your current email marketing platforms.

• Cost-effectiveness: Assess the tool’s pricing against the features and value it offers and choose a tool that fits your budget while meeting your email marketing needs effectively.

Omnisend

Note: To test Omnisend and the rest of the tools on this list, I used the subject line “There’s a reason people LOVE these sofas,” which recently caught my eye in my inbox. Also, as it is quite a creative one, I thought it might be a great fit to see how the testers work 🙂 

Number one on the list is a great subject line tester tool from the marketing automation platform Omnisend – a tool that promises to get you higher open rates and the first result for the “email subject line tester” Google search.

When I first opened up Omnisend’s subject line tester, the page struck me as a regular landing page, but boy, did I discover more! Upon clicking the bright green “Test now” button, the page transformed into a big, beautiful report. 

On the report, you first get an overall score for your subject line. Then, put to the test are the subject line’s character count and word count, which also receive a score and an explanation of the best character/word count practice.

A very cool addition was the wording analysis. Here, my subject line was flagged for not having helpful words that would increase email open rates, and I was provided with a list of options that do the trick. Luckily, it passed the negative words check!

The rest of the report is comprised of a scannability check, which takes a look at the use of numbers as well as the capitalization style, and a preview of the subject line on desktop and mobile devices to test readability.

I must admit that the latter was a bit disappointing as the preview was presented in an “artsy” way, leading me to confuse it for a graphic design on the page. Maybe it’s just me, but I’d prefer a more realistic preview rather than one on an illustration of a Mac and iPhone.

Pros:

• Comprehensive
• Easy to use 
• Analysis based on best practices and industry benchmarks

Cons:

• Lacks suggestions such as personalized ones

Pricing:

• Free 

Support:

• Contact form
• Email
• Live chat

Subject Line Tester by Send Check It

Off the bat, Send Check It’s tester looks very similar to the one offered by Omnisend – one big input field and a bright button at the top of the page, basically calling your name to test email subject lines. 

Upon clicking the tool’s “Test Subject Now” button, you might get caught a little off guard (at least I was) by the pop-up form asking you to sign up in order to actually use the tester.

But once you’re done with the minor sign-up hurdle, the page will finally generate a subject line analysis!

In the analysis, you first have an overall score and a suggestion for making tweaks but without much actionable advice. Then, you have check results for scannability, reading grade level, and length, all accompanied by information on what a good average score is and some general advice on how to improve yours.

Now, when it came to the email subject line preview part, I was again a tad disappointed. 

The preview was, in this case, also shown in an “artsy” manner, but the bigger issue was the inaccuracy of the preview. For my specific example, it said that the subject line is not visible in full on desktops when, in reality, and in my Gmail inbox, it absolutely is.

You see, the subject line is shown in full, along with the sender’s name.

After the poor preview, there was still a lot of the analysis to go through, including sentiment, personalization, and the presence of things such as “RE”, “FWD”, spam words, bad tab words, exclamation marks, all caps, and excessive punctuation.

The rest consisted of suggestions, such as ones regarding the reformatting of your subject line as a question, using all lower cases, and including emojis.

Pros:

• Very in-depth analysis
• Subject and headline testing API

Cons:

• Vague feedback 

Pricing:

• Free (unlimited access to a custom API endpoint requires a small fee)

Support:

• Email

Headline Analyzer by CoSchedule 

CoSchedule’s headline tester is a tool designed to help users create not just effective email subject lines but also headlines for various types of content, including blog posts, YouTube videos, podcast episodes, TikTok videos, and Instagram posts.

In terms of aesthetics, this tester doesn’t differ almost at all from the two previous ones I covered. The only new addition would be the drop-down menu, which allows you to pick what exactly you will be analyzing. 

And just like Send Check It’s tester, this one also comes with an unexpected signup form that pops up upon running the analysis.

After completing the signup, your analysis does not continue running; instead, you’re led to the HeadlineStudio dashboard and forced to restart the process. Frustrating? A bit! But, once the analysis is done, you’re met with an impressive report.

In the report, there are three tabs: headline score, SEO score, and headline AI.

The first tab generates your regular subject line report, where information is presented on subject line length, reading grade level, sentiment, clarity, and skimmability. Within the same tab, there is also a word balance section that breaks down the balance of common, uncommon, emotional, and power words in your subject line. 

If you have a lack of any of the mentioned word types, a link to a “Word Bank” is provided!

The second tab (Premium feature), although very cool with its SEO report, is not so useful for email subject line testing but more for creating blog post headlines.

Finally, the third tab (also a Premium feature) offers a fun AI-powered chat in which you can ask questions and make the AI algorithm list new and creative alternatives for your original subject line.

Pros:

• AI assistance
• Headline version history 

Cons:

• Useful features hidden behind a paywall 

Pricing:

• Free plan and paid plans starting at $4/month

Support:

• Video tutorials within tool
• Email
• Chat

Mailmeteor

Besides offering features that facilitate the sending of personalized mass emails, Mailmeteor also offers a subject line tester that completes two tasks once you feed it a subject line:

1. It grades the performance of your subject line and, within the same report, also breaks down the metrics used to determine the grade. 

2. It suggests a list of different subject line alternatives generated by AI. Each of these is also graded on performance, so you know what to expect if you decide to go for one of the alternatives or use them to conduct A/B testing.

Looks all too simple? It kind of is! But, if the tool’s website is to be believed, with Mailmeteor, email subject lines are inspected on multiple levels. On top of that, its testing and generation speed might be the fastest on the market!

Pros:

• Short and to-the-point AI-generated subject lines 
• Performance predictions for AI suggestions

Cons:

• Low-performing subject lines sometimes offered as suggestions  

Pricing:

• Free

Support:

• Knowledge base/documentation
• Contact form 

Email Subject Line Grader

Net Atlantic’s free Email Subject Line Grader is a tool for those of you who like to keep things simple, as its landing page has so few elements that you can count them on your fingers.

However, upon running a subject line analysis, the page starts to offer more!

First on the page is a, you guessed it, overall score. Then, you’re met with a categorization of your subject line into a specific subject line type and suggestions for how to make it more effective.

Character and word count are also rated on the page, with each rating being accompanied by an explanation of how to interpret your results and/or how to improve.

Lastly, you have a breakdown of your word mixture and balance where you see what percentage of action, power, and emotional words your subject line consists of.

Pros:

• Tool page dedicated to testing only (no CTAs, marketing copies, etc.)

Cons:

• Geared towards experienced email marketers due to its extreme simplicity in suggestions

Pricing:

• Free

Support:

• Email (through Net Atlantic)

Subject Line Tester by Email Tool Tester

Email Tool Tester’s Subject Line Tester takes a unique approach by focusing primarily on how your subject lines will actually appear across different mobile devices.

Unlike other tools that provide extensive analytics and scoring, this tester specializes in realistic visual previews.

The tool supports current popular devices including iPhone 14, iPad (10th Gen), Google Pixel 9, and Samsung S25 Ultra, showing you exactly how your subject line will display in standard email clients on each device. This addresses a common pain point with other testers that often provide “artsy” or unrealistic previews.

One standout feature is the AI-powered emoji suggestion functionality, which can help you enhance your subject lines with relevant emojis to improve engagement. The tool also includes a character counter to help you stay within optimal limits.

The interface is refreshingly simple – just input your subject line details (sender name, subject line, and preview text) and get an immediate visual preview. There’s no sign-up requirement, making it instantly accessible.

Pros:

• Realistic mobile device previews
• AI-powered emoji suggestions
• No sign-up required

Cons:

• No scoring or performance predictions

Pricing:

• Free

Support:

• Contact form

Email testing beyond the subject line

Email subject line testing is crucial as subject lines are often the first thing a recipient sees and uses as a deciding factor for whether to open or ignore your email. That said, subject lines are not where your testing efforts should seize.

You see, an email, especially in HTML format, is prone to having errors oftentimes unnoticeable to the sender. To avoid sending email messages with such errors, a proper testing tool is necessary. 

Email Testing, part of the Mailtrap Email Delivery Platform, is such a tool you can use to inspect and debug emails.

With Email Testing, you can check how supported the HTML and CSS code of your email template is by popular mailbox providers. 

You can also take a deep dive into your spam check report and see how likely you are to get flagged by spam filters and hurt your email deliverability or if your sender domain/IP is present on any commonly used blacklists.

Email previews are, of course, also included within Email Testing, allowing you to check how your email looks further down than the subject line on different screen sizes, if the links and buttons are functional, are all images getting displayed, and other things related to rendering.

So, how do you start using Email Testing? It’s easy!

First, you’ll need a Mailtrap account. 

Then, if you’re a dev or a tech-savvy digital marketer, you can use the SMTP or API settings generated by the tool to integrate it into your application. 

If, on the other hand, you prefer to skip dealing with any of the mentioned settings, you can opt for using a dedicated email address linked to your Mailtrap virtual inbox to send test emails to and analyze them within Email Testing.

Once you’re done testing, within the Mailtrap Email Delivery Platform, you also have a tool offering a reliable Email API and SMTP service you can use to send your now-perfected emails to recipients!

Wrap up

There is no shortage of email subject line testers on the market, standalone or within platforms such as Mailchimp, Moosend, etc. So, if none of the abovementioned email subject line tester tools suit your preference, feel free to use my comparison criteria to evaluate your own picks. 

But if you do happen to find what you need in this article, rest assured that during my research, I only chose options that will get the job done properly. With such tools, you’ll be ready to create better email marketing campaigns with higher open rates, click-through rates, no spammy words, and overall success!

Want more content on email testing? Check out some of our other articles:

• How to Test Emails in Different Clients | Mailtrap Blog 
• Email Marketing A/B Testing: A Step-By-Step Guide [2023] 

Also, make sure to visit our YouTube channel, where we cover all things email!

And, in this article, I’ll provide you with the email deliverability tools you need to conduct these tests, show you how to use them, as well as break down:

• The results of email deliverability tests we’ve performed [jump ahead]
• How to test email deliverability and its different aspects [jump ahead]
• The criteria I’ve used to select the testing tools on this list [jump ahead]
• The features, pricings, and other nuances for each tool [jump ahead]

To freshen up your knowledge on email deliverability itself or learn a bit extra about it, be sure to check out our dedicated article on the topic.

Email deliverability testing tools: a snapshot

To make it easier for you to choose and for a more well-rounded selection, I’ll showcase 1 tool for analyzing email content in a sandbox, 2 email deliverability and spam testing tools, and 2 sender reputation and domain health tools. These include:

• Email Sandbox for devs and QAs to inspect and debug emails in a safe environment, as well as for marketers who want to see how their emails perform from different angles. 
• GlockApps for users who want an in-depth deliverability solution that comes at a price.
• MailerCheck for those who want a more minimal and affordable GlockApps variant.
• SenderScore for those who are just getting into email marketing and or who want to test their personal projects’ deliverability.
• MXToolbox for either users who need a simple free solution or those who want advanced testing tools that come with the paid plan.

And for your convenience, here’s a chart with a brief overview of each testing tool:

Email deliverability test results

To show you why testing email deliverability is important, let me share the results from one of our most recent tests we conducted with GlockApps.

Essentially, we used free plans, the same template, and shared IP, and we didn’t warm up the domains to ensure the test was fair and square for every provider. Here are the results:

Now, some of the things we can conclude based on these results are:

• Major mailbox providers face recurring deliverability issues.
• Free ESP accounts significantly impact deliverability.
• Google Spam filter is the least likely to block any emails.

Knowing this, you can more adequately choose your ESP, adjust the emails you send to Outlook or Yahoo users since they have stricter filtering, improve your email engagement for Gmail or Google Workspace since they send most emails to promotion tabs, and more.

On top of that, by properly testing your email deliverability, you avoid losing money on undelivered emails ($0.11 per email, more specifically). 

Important: As email delivery and deliverability are often intertwined and misused, it’s important to make the difference between the two. In short:

• Delivery refers to whether a recipient’s mailer server accepted your email.
• Deliverability is about whether your email was delivered right into the recipient’s inbox or it found a way to their spam folder.

If you’re interested in more details, check out the video we prepared for you. ⬇️

How to test email deliverability

Email deliverability could be broken down into technical, sending, and content aspects:

• Technical – Free or shared IPs, IP’s warming up, email authentication protocols. 
• Sending – Domain, IP, sender reputation, how users engage with your emails, your  sending schedule, your email list and hygiene, etc.,
• Content – Subject line and message personalization and relevancy, having an unsubscribe link, readable HTML template, click-through rate, open rate, and so on.

For this article, I’ve selected the tools for testing each of the aspects. However, although you could test each aspect separately with different tools, you can’t test one without the other since every aspect depends on other aspects. 

What I mean by this is that you can have the perfect technical setup, but your emails won’t be relevant, or, even worse, they might get sent to a dead email list, which will negatively impact your email deliverability rates.

So, you can use Email Sandbox to test emails in a sandbox before sending them live and leverage MxToolbox to validate DNS records. Or, you can use GlockApps to simulate real-world inbox placement and leverage MailerCheck to analyze email content and engagement impact. You get the idea.

And if you feel like diving further down the email deliverability rabbit hole, be sure to check out our in-depth guide on the topic. 👀

Email deliverability testing tools: choosing criteria

Let’s be frank: a simple Google search will give you more email deliverability testing tools than you can count. So, to narrow the selection down and provide you with crème de la crème, I’ve considered the following criteria:

• Range of features – Some of the features I’ve looked for include: spam checker, email preview, inbox placement tests, and deliverability insights. Anything else, like email validation, was just a bonus.
• Ease of use – Since deliverability as a concept and as a problem to solve is a bit difficult on its own, I skipped any tools with a steep learning curve. So, I provided you with tools you can get the hang of quickly, so you can focus on improving deliverability right away.
• Analytics – Besides making sure your emails are landing in inboxes, it’s also nice to know if the opens, clicks, bounce rates, subscribes and unsubscribes, and more. These are only some of the key email marketing KPIs.
• Pricing and affordability – Since the cost of undelivered emails is already high, you don’t want a tool that’ll break the bank. That’s why I skipped all of the tools out there that cost more money than the amount of undelivered emails cost you.
• Customer experience – I went through the most popular review websites, such as G2, Capterra, and Trustpilot to find out what others who have used the particular service think. Of course, I also made sure to check out social media platforms.
• Use cases and target audience – As I’ve said previously, you can combine all of the tools in this list one way or another. However, each is fit for certain cases and audiences, so essentially, there is something for everyone here.
• Support and documentation – Basically, you don’t want to use a tool that’ll feel like solving a riddle. So, every service on this list has either rich documentation and support for whenever you’re facing a blocker or both.

Disclaimer: The ratings, features, and prices are up-to-date as of writing this article, but they could be different when you’re reading it as they’re prone to change.

Email deliverability testing tools

Email Sandbox – Deliverability and email content analysis

G2: 4.8 🌟 Capterra: 4.8 🌟

Email Sandbox provides you with a safe environment to inspect and debug emails in staging, dev, and QA environments. It also lets you preview and analyze content for spam and validate HTML/CSS before sending emails to recipients in production.

The service is geared towards developers and marketers who want to focus on high deliverability while having in-depth analytics, 

How to use Email Sandbox

To test your email deliverability with Email Sandbox, follow these steps:

• Create a free Mailtrap account.
• Go to Email Sandbox → Inboxes.
• Open My Inbox (created by default).
• Select SMTP/API/POP3 under Integration.
• Copy/paste the provided credentials or code samples into your email-sending script.

• Send the email from your application/project.

Once the email arrives in your inbox, you’ll be able to see how it looks in HTML or raw text, get detailed HTML and spam checks and other tech info.

And for all of you visual learners out there, here’s a quick video tutorial on how Email Sandbox works. 👀

Additionally, you can also test your deliverability post-deployment if you choose to send emails with Mailtrap’s SMTP/API service or the Email Marketing suite. This way, you’ll get the most important deliverability metrics, such as delivery rates, open rates, clicks, spam, and more.

You can also set email categories to determine which type of email performs best with your audience. This is also useful for managing email marketing campaigns or performing A/B testing.

Email Sandbox features:

• HTML/CSS support – Check how your emails look with the most popular mailbox providers. 

• Email preview – Preview your emails in HTML, raw, source, and more.
• Spam score check – Improve your email deliverability rates and prevent your emails from going to spam by keeping your spam score under 5.

• API for QA automation – Cover all of your testing scenarios with our Email Sandbox API.
• Ready-to-use integrations in 20+ languages (Ruby, Python, Node.js, etc.) – Easily integrate your application with Email Sandbox 
• Multiple inboxes for different projects and stages – Quickly find your data, switch between tasks, or share your testing results with colleagues or clients.
• Templates testing – Test your email templates with our API and then easily switch from staging to production environment once you’re ready to start sending. 

• Google Postmaster integration – Provide our deliverability team access to your Google Postmaster dashboard and get additional support and tips.

Pricing

Email Sandbox pricing plans are super simple: you have several tiers to choose from based on price, monthly test emails, and additional features that come with it, such as manual forwarding, maximum emails, etc.

Here they are summarized in a table:

It’s worth noting that the Email Sandbox Team Plan is free for Open Source non-profit organizations or educational institutions. Additionally, SMTP/API services come together with the Email Marketing suite on the Sending plans.

For more details, please visit the official Mailtrap pricing page.

Customer experience

When it comes to online reviews, I’ve noticed a lot of people are enjoying Email Sandbox. A lot of users, like the one in the screenshot below, like the fact that they don’t have to worry about sending emails to real recipients:

Bonus: Check your sender reputation with our free Domain Blocklist Checker and IP Blocklist Checker tools as well!

GlockApps – Email deliverability and inbox placement

G2: 3.7 🌟 Capterra: 4.8 🌟

GlockApps is an email deliverability testing tool that offers several tools for diagnosing deliverability and security issues, monitoring email placement, and improving the odds of your emails reaching your recipients’ inboxes.

The service is best for those who need an in-depth deliverability solution and can spend an extra few bucks on it.

The main GlockApps feature I’ll cover in this article is Inbox Insight, which allows you to see how your emails perform across different ISPs like Gmail, Office, or Outlook. It does this by emulating email-sending through Postfix and two other platforms for sending emails. It then estimates where your email would land. 

How to use GlockApps (Inbox Insight)

• Log in to your GlockApps account.
  • You have 3 tests with the free account.
• Select Inbox Insight → Dashboard on the left-side menu.
• Click on Start Spam Test.
• Select the Manual Test Start.
  • You can also automate GlockApps to test each campaign before you send them.
• Choose the spam filters and email providers you want to test against.
• Select the folder to store your report to and add any notes (optional).
• Click on Create.
• Copy the message ID into your email and paste the provided email addresses (also known as Seed List) to the ‘To’ field.

Lastly, after sending your email, go to the Reports section, where you can see your email placement results, IP analytics, domain analytics, and more.

Moreover, you can also use GlockApps’ DMARC Analyzer, which provides you with in-depth and user-friendly DMARC analytics, weekly reports, dedicated support, and other little tools you can use to keep your email communication secure and maintain your sender reputation.

Or, you can monitor the health of your SPF, DKIM, and DMARC records, keep track of any potential downtimes of your website, and get notified if your IP gets blacklisted.

Features

• Domain analytics – Check for issues like spoofing or phishing attempts and monitor your domain’s reputation.
• Spam score – Evaluate your emails against major spam filters and get a spam score to optimize your email content.
• Cold email outreach tests – Test cold email campaigns and see how well they deliver and how much your recipients engage with them.
• Proxy tests – Evaluate how your emails perform across different networks and configurations.
• Personalized email deliverability consulting – Book a 1-hour consultation with one of GlockApps’ deliverability consultants.
• Google Postmaster integration – Similarly to Mailtrap, GlockApps allows you to integrate the Google Postmaster dashboard for extra stats.

It’s also worth noting that GlockApps offers a plethora of basic free tools, such as spam, DMARC, MX, TXT, and other checkers. 

Pricing

As of writing this article, GlockApps offers separate plans for Spam tests and DMARC analytics. However, they also have a Bundle plan, which brings the best of both worlds together:

For more details, please visit the official GlockApps pricing page.

Customer experience

Whether I went on Reddit or X, or even Trustpilot, I’ve seen nothing but positive comments on GlockApps, similar to this one:

MailerCheck – Email list verification, deliverability, and inbox placement

G2: 4.5 🌟 Capterra: 4.9 🌟

To quote its creators: “MailerCheck is a “more affordable GlockApps alternative that offers flexible plans for businesses as well as a reliable email verification tool.” After giving it a try for some time while preparing this article, I’d say that is true, but only to some extent.

Namely, MailerCheck is for people who need a more minimal and affordable GlockApps. So, inbox insights, usage reports, and monitoring, just without the advanced features like Postmaster integration, email logs, uptime monitoring, or deliverability consulting.

How to use MailerCheck

• Log in to your MailerCheck account.
• Go to Inbox Insights on the left-side menu.
• Enter your report name and description (optional).

• Check Email Insights and click OK.
  • You can also use the Inbox placement feature to check how your emails perform with different providers, but for this, you’ll need twice the credits.
• Copy/paste the provided email address and send your email campaign to it.

The results should come in a minute or two both on the dashboard and your inbox, where you’ll be able to see whether your emails passed spam filters, whether your HTML is on point, and more.

Features

• Bulk email validation – Keep your email list clean by removing invalid, harmful, disposable, and other addresses by running them through MailerCheck’s validator.
• Real-time API verification – You can also use MailerCheck’s validation API to validate new addresses as you collect them, instantly filtering out the faulty ones.
• Usage reports – Get insights on your email lists and improve your deliverability by sending emails to users with valid addresses who are more likely to engage.
• DMARC monitoring and reporting – Keep track of your domain use and troubleshoot your deliverability in real-time.
• Blocklist monitoring – Get alerts when your IP address or domain appears on a blacklist.

Pricing

First things first, MailerCheck offers a free plan, which you can use for a single deliverability check. However, you can also use it to validate 200 emails.

On the other hand, the pricing is quite fair I’d say, although the curve is a bit steep for the higher-end plans, which is why I don’t think it’s more affordable than GlockApps.

Nonetheless, check it out for yourself:

But, there is also the option to pay as you go, which lets you purchase between 1,000 to 5,000,000 credits. This can be useful if you’re a single-time user or want to check out the platform.

For more information, please consult the official MailerCheck pricing page.

Sender Score – Sender reputation and domain health  

G2: N/A Capterra: N/A

Sender Score is a free email deliverability testing tool by Validity, which you can use to monitor your sender reputation, see if your domain is on blocklists, and more.

Since it’s a free solution and doesn’t offer any advanced features, I’d say this tool is best for those who are just getting into email marketing and deliverability in general. Or those who need a quick test for their project before they switch to a paid solution.

How to use Sender Score

• Open Sender Score in your preferred browser
• Enter your domain or IP address 
• Fill out the additional information and click What’s my score?

In a few moments, you’ll be able to see your sending domain information, SSL information, sending IPs, and more.

Then, you can go to Access → Deliverability Benchmarks and see how you fare to others in your industry. Simply enter your email, choose your sending amount, and click on See the global averages.

Features

• Blocklist lookups – See if your domain is being blocklisted.
• List quality checks – Upload your contact list and have it validated by BriteVerify, another part of Validity. 
• Email revenue calculator – Use Sender Score’s revenue calculator to get a prediction on the potential of your campaigns’ earnings. 
• Deliverability consultation – Get a free 1-hour consultation with one of Sender Score’s email deliverability experts.
• Bounce lookups – Check why your emails are bouncing and significantly improve your deliverability.
• Subscriber list analyzer – See which mailbox providers make up the majority of your email list. 
• Subject line preview – Test your subject lines and pre-headers across 20 email clients and see how they perform.
• Blocklist remover – In case your IP is blocklisted, you can enter your IP address and check if it’s on the return path blocklist.

I’d also like to point out that Sender Score has a great knowledge base, where you can learn a lot on deliverability and all things email through podcasts, video lessons, and newsletters.

Customer experience

To be honest, I haven’t found many reviews of Sender Score online. However, I’ve noticed that many people mention it in lists on improving email deliverability and found no complaints. Unfortunately, no reviews. 🙁

MxToolbox – Sender reputation and domain health 

G2: 4.0 🌟 Capterra: 4.5 🌟

MxToolbox is a service launched way back in 2004, offering various tools aimed at helping improve the domains’ capabilities. 

Since it’s free (if you don’t want the extra features), MxToolbox is best for people looking for a quick deliverability check.

How to use MxToolbox

The MxTool I’ve used the most is the deliverability tool, which allows you to validate your domains’ email authentication methods. 

To use it, all you need to do is send a test email to ping@tools.mxtoolbox.com. Shortly, you will get an email in your inbox (check the Updates tab) with the test results. 

Click on ‘View your full deliverability report,’ and you’ll see the detailed report.

Features

Besides allowing you to test your domains’s authentication, MxToolbox also offers tools for:

• Performing blacklist checks 
• Looking up DNS records 
• Checking domain health  
• Performing reverse lookups
• Testing email servers 
• And more.

You can use all of these features by visiting the MxToolbox SuperTool.

Pricing

If the free tools MxToolbox is offering are not enough for you, you can switch to one of the paid plans, which are quite simple;

For more details, please visit the official MxToolbox pricing page.

Customer experience

Having been launched in 2004, it’s no surprise that the veteran of the email game MxToolbox has a plethora of positive reviews online. Whether it’s Trustpilot or Reddit, you can find only praises about it.

Ready, set, test

And with that, we’ve reached the end of our article!

Now, all you have to do is choose your tool(s) and test your email deliverability! The choice is completely up to your preferences, but we sincerely hope Mailtrap makes the cut!

One for the road: You can also test email deliverability manually. Learn how to do that by watching the step-by-step video we’ve prepared for you:

Today, I’ll take you with me on a journey of understanding what blacklists are and how they work. I’ll also show you what I had to do to get unblacklisted and how I prevent getting booted off the email grid from happening again.

Let’s dive right into it!

What is an email blacklist?

An email blacklist is a database of IP addresses or domains suppressed for malicious behavior. It also goes under the technical names of the Domain Name System-based Blackhole List (DNSBL) and Real-time Blackhole Lists (RBL). 

Major email service providers (ESPs) such as Gmail, Outlook, and Yahoo all have their own email blacklists that are regularly updated and shared amongst each other as well as with internet service providers (ISPs) and anti-spam vendors.

Types of email blacklists

There are about 5 types of email blacklists, but things can get a bit confusing, so stick with me while I explain.

First, you have domain-based and IP-based blacklists, where the main difference is that domain-based blacklists focus on the sending domains, while IP-based blacklists focus on the email server IP addresses. 

Then there are public and private blacklists, where one is accessible to the general public, and the other is reserved for the use of major mailbox providers and requires a license to be accessed.

Finally, enterprise spam firewalls are a type of blacklist provided and maintained by independent organizations such as Spamhaus, Spamcop, Invaluement, and Barracuda and are used as a security mechanism by IT departments.

Among the popular blacklists, you will find a mix of all the mentioned types, with the 10 most popular lists being:

• Spamhaus Block List (SBL)
• XBL Exploits Block List
• DBL Domain Block List
• PBL Policy Block List
• Composite Blocking List (CBL)
• Spamcop
• Invaluement
• Barracuda
• Passive Spam Block List (PSBL)
• SenderScore

How does an email blacklist work?

Email blacklist filters work by helping ISPs decide if an email should be accepted or rejected. And they’re part of a complex email filtering process that looks something like this. 

After an email has been sent, it reaches an ISP. The ISP then checks the email’s IP addresses, domains, or hashes against various blacklists to determine if they are listed. Additionally, as a second layer of defense, spam filters analyze the message to ensure it complies with ISP policies and does not contain malicious or unwanted content.

If an email passes both checks, it is delivered to the recipient’s inbox.

If it does not pass, the email may either be completely rejected or accepted with a tag allowing further filtering by the recipient’s email system.

For a visual explanation of how and when a blacklist is used, check out the graphic below created by Spamhaus:

What are the reasons to blacklist an email address?

Poor email list hygiene 

On an email contact list with poor hygiene, you’ll find lots of inactive addresses as well as a few spam traps. Sending emails to inactive subscribers will demonstrate potential neglect of honoring unsubscribe requests while emailing spam traps might raise suspicions that you bought your email list or don’t implement opt-in solutions.

A lot of spam reports

Spam reports are something every email sender will have to deal with. However, if the number of spam reports against you is significant, ISPs have no choice but to blacklist you. And although an increase in spam reports could happen for a range of reasons, it usually stems from general uninterest from your audience or lack of proper opt-ins.

Poor or spammy email content

Content with an overly promotional tone, spam words, or content that lacks relevance can often trigger not just ISP filtering mechanisms but also recipients to flag you as a spammer. So, before using keywords such as “money-back guarantee”, all caps, and excessive exclamation marks or skipping on creating engaging and valuable content, do keep in that it could be a fast track to blacklisting.

Hacked or compromised email account

In the case of hacking, your account will be used to send large amounts of spam messages at a time. In less serious cases, your email could get spoofed, and your IP address could be used to send fraudulent messages. Both of these activities, when registered by ISPs, will ruin your sender reputation and cause immediate blacklisting.

Spikes in the volume of outbound emails

Inconsistency in outbound email volume is almost always a characteristic of malicious email senders. So, if you have a sudden and sharp spike in your daily sending volume, ISPs might consider it suspicious activity and blacklist your IP/domain in turn.

Malware infection

Sending emails from a malware-infected system is guaranteed to prevent inbox placement. So, if your system is compromised by a virus, spambot, Trojan, or any other type of malware, it will not only harm your email deliverability but will also likely result in your immediate placement on a blacklist.

How to check if your email domain is blacklisted

Use spam report information

Spam reports can be a goldmine of insights into if and why your emails might be landing in the junk folder, and depending on the tool you are using to generate them, you might even get a dedicated blacklist report for your IP or domain. 

Mailtrap, for example, comes with a built-in spam checker intended to prevent your emails from going to spam and improve deliverability. We also developed free tools for this, our Domain Blocklist Checker and IP Blocklist Checker.

For each email sent, the spam checker will generate a spam report using Apache SpamAssassin, which includes a general score and a detailed table with spam test points and their descriptions, as well as a blacklist report.  

Through the blacklist report, you can gain insight into whether your IP or domain has been listed on any of the commonly used blacklists, see resources that have been queried, and check your current blacklist status. Also, in the case of your IP or domain being blacklisted, Mailtrap’s spam checker will provide you with the name of the blacklist and a hyperlink to its website so you can quickly check the rules for delisting and follow the instructions.

Use blacklist checker tools and blacklist monitoring tools

As blacklists can be divided into IP-based and domain-based categories, the blacklist checkers available to you also come in two different forms. Still, regardless if you need an email IP blacklist checker or an email domain blacklist checker, make sure your pick is a publicly available tool, as they are quick and easy to use.

Here are the most popular ones to check out:

• MX Toolbox
• DNS Stuff
• DNSBL
• MultiRBL 
• Spamhaus

Along with blacklist check tools, also consider using a blacklist monitoring tool such as HetrixTools and Debouncer that will continuously check your IP or domain and notify you if you’ve been added to or removed from any list.

Monitor email deliverability rates

Even if you haven’t directly noticed a blacklist issue yet, dips in your deliverability rate could be a sign that your messages are getting blocked or sent to spam. To catch these red flags early, regularly analyze your email campaign reports for any patterns or sudden drops in engagement. 

Listen to feedback from email service providers

Modern email service providers come with features for flagging sudden spikes in spam complaints, high bounce rates, and other deliverability issues. So, one of the simplest ways to detect a possible blacklist issue is by paying attention to direct notifications or warnings from your email platform, like feedback loops, for example. These alerts often come with basic insights or error messages that point you toward the root of the issue, such as your domain or IP address being blocked.

How to get off an email blacklist

If you ended up in the same situation as me and found yourself on one or more blacklists, not all hope is lost, and you can still clean up your email sender reputation. 

Here’s how I did it!

Step 1 – Find the cause 

Once you suspect that you’ve been blacklisted or a simple email blacklist lookup confirms it, your first action should be pinpointing why you ended up on a blacklist in the first place. 

In my case, I went straight to my recent campaign’s email deliverability, engagement, and spam reports and checked for any notifications or warnings I might have missed that could give me a clue.

Step 2 – Fix the issue 

With the problem that caused the blacklisting identified, it’s time to do the necessary fixes. As for me, the issue came from an outdated email list; I proceeded to clean it by removing inactive and invalid addresses. I also ran a permission pass campaign to confirm with the rest of my email list that they are still interested in receiving emails from me.

Depending on what the issue is for you, you might be implementing proper authentication, rethinking your email design and copy, or doing some other type of task.

Step 3 – Request delisting 

The third and maybe the most important step is reaching out to the blacklisting entities and submitting a request for delisting. Of course, I only did this after implementing corrective measures and collecting proof of doing so. 

The delisting request will often entail you filling out a form in which you explain what issues were addressed and show commitment to following best email-sending practices moving forward. But do keep in mind that delisting might not be instant and that for some blacklists, you might even have to complete additional steps before removal is initiated.

If all fails, start from scratch

Although I was lucky enough to be able to fix my issue (and you probably will, too), there is still a chance that a sender could stay blacklisted forever. In that case, starting over with a new domain or IP is the only solution. On top of that, using proactive measures is also a must. Otherwise, you will again get quickly put back on a blacklist.

How to avoid getting blacklisted

Regardless if you’re like me and have been blacklisted before or you’ve never been in email sender timeout, we have a common goal – staying off of blacklists. 

To achieve this goal, I created a list of best practices, which include:

Run spam tests

Spam testing is a practice I implement not just for figuring out if I’ve been blacklisted but also for preventing blacklisting from happening in general.

Of course, in both cases, the spam checker I go for is the one from Mailtrap, as it enables me to:

• run in-depth email spam tests and get a detailed list of spam points and HTML spam rules they go against
• inspect the email subject line, email body, and attachments, and remove any malicious or broken links
• and check if my sending IP address or email domain has been mentioned on any major public blacklists

Using this spam checker, I test all my emails including newsletters, email notifications, cold emails for outreach, or email marketing campaigns. And since all the emails I send to Mailtrap get captured by a fake SMTP server, my testing never causes any actual bounces. 

Pretty convenient, right?

Implement proper email authentication

When it comes to the technical aspect of preventing blacklisting, with every email provider I use, I always make sure to configure SPF, DKIM, and DMARC for my domain.

SPF is there to check that my emails are sent from authorized mail servers, while DKIM adds a digital signature to verify authenticity. Finally, DMARC ties everything together, letting me decide how to handle any suspicious emails. 

Maintain your email lists

Considering that poor email list maintenance is what led to me getting blacklisted, I now take multiple precautions to ensure I am only sending to real accounts and people who are genuinely interested in my emails.

Never buy email lists

First and foremost, I steer completely clear of using purchased email lists. These lists are often outdated, full of invalid addresses, or even worse – spam traps designed to catch bad senders. Building your list organically may take more time, but it’s the only way to ensure your emails reach real, engaged recipients.

Regularly clean your lists

Over time, even the best email lists collect bad data. That’s why regular cleaning is a must and should include:

1. Removing bounced emails: Hard bounces should be removed immediately to avoid harming your sender reputation while soft bounces should be monitored closely, and if they keep repeating for the same email address, consider removing it from your list as well.
2. Analyzing engagement: Pay attention to who’s opening your emails and who isn’t. If someone hasn’t engaged with your campaigns in months, send them one re-engagement email, and if that fails, remove them from your list.
3. Honoring unsubscribe requests: Always respect requests to opt out of your emails. Not only is this the right thing to do, but it’s also required by laws and regulations.

Segment your lists

The email addresses on my list are segmented and grouped based on factors like location, purchase history, or interests. By doing this, I send more personalized and relevant emails, increasing engagement and reducing the chances of ending up in the spam folder. 

Send only good content

To increase my chances of landing in inboxes, I focus on clear messaging that resonates with my audience and steer clear of deceptive subject lines, trigger words like “free” or “cash bonus”, excessive punctuation, and all caps. Along with that, I find that personalization is key—whether it’s as simple as addressing recipients by name or tailoring offers to their preferences .I’ve also learned to maintain consistent email-sending frequency, avoiding sudden spikes that might irritate my audience or trigger delivery issues.

Build trust with subscribers

Building trust with subscribers starts with gaining explicit consent through transparent opt-in forms and honoring their preferences. So, in every email I send, I include a clear unsubscribe link to make opting out easy. For ensuring only real, interested people join my list, double opt-ins are my go-to.

Remind subscribers to move your email to their inbox

When an email address or domain gets blacklisted, it often means the messages sent from it will be automatically routed to spam. To prevent this, in the past, I’ve encouraged my subscribers to “whitelist” my emails, or in other words, move them into their inboxes or add me to their safe sender list. 

Wrapping things up

In this post, we covered everything you need to know about email blacklisting – from what causes it in the first place to what fixes should be made to repair the damage done. So, if you’ve never been blacklisted before, use the information from this article to lower your chances of it ever happening. On the other hand, if you currently find yourself on a blacklist, follow the steps I outlined to improve your situation and make ISPs, as well as recipients, trust you again. 

If I’ve successfully navigated the rough email blacklist waters, you can too!

• What is email client testing?
• Email client testing tools – quick overview
• How to choose the right email client testing tool
• How to test emails with different clients

What is email client testing?

Email client testing evaluates how an email renders and functions across various email clients, devices, and operating systems. The primary goal is to ensure that the email displays correctly and consistently for all recipients, regardless of the platform they are using.

For instance, an email might look perfect on Gmail in a web browser but could have broken layouts or missing images when viewed in AOL or Outlook on a desktop or Yahoo Mail on a mobile device (iPhone or Android). 

Anyway, email client testing helps identify and rectify such issues before the email is sent, ensuring a seamless experience for all users.

Here are a couple exemplary use cases:

1. Cross-client rendering: An email designed for a marketing campaign is tested across different platforms like Gmail, Outlook, and Apple Mail. During testing, it’s found that some CSS styles are not supported in older versions of Outlook, leading to a broken layout. The issue is addressed by implementing fallback styles specific to Outlook.

2. Mobile responsiveness: A promotional email is tested on various mobile devices using different email clients like the Gmail app on Android and Apple Mail on iOS. The testing reveals that images are not scaling properly on smaller screens. This prompts the design team to adjust the email’s media queries to ensure images resize correctly on all devices.

Email client testing tools

It’s not hard to guess that these tools allow you to see how your email looks across different devices and email clients, identify rendering issues, and make necessary adjustments. 

But not all pro tools are the same. Generally, they can be divided into three categories:

1. Independent or standalone testing tools (I tell you exactly how to use them, just hit the link)
2. HTML preview tools (check the overview below)
3. Email preview as a feature of a much larger platform (also check the overview below)

The bottom line is that you may choose one type of a tool over the other depending on your preferences and the current tech stack. They all aim to improve email deliverability by checking formatting, email design, and the code behind it. 

But keep in mind that some tester tools won’t show which lines of code are problematic and may not offer suggestions on how to rectify them. 

HTML preview tools

The approach here provides HTML and CSS analysis with a list of issues for every popular email client. 

I’ll give you a quick overview of some of the tools offering previews. And if you want to find out more about them, we already have a detailed guide, so hit this link. 

The main thing is that HTML email analysis tools don’t just generate a preview for each email client but indicate exact problems in your code and explain how to fix them. 

This means that you don’t need to go through a bunch of email client preview windows looking for possible issues (some tools may have 60+ previews) —  the HTML/CSS tool has already analyzed it for you and shared the results in a report.

Also note that, the majority of email preview tools show how your HTML is rendered in a browser and how it looks on desktop, tablet (iPad and the likes) or mobile devices.

Email preview as a feature

As mentioned, email client testing can be found as a feature of much larger CRM or email sending tools. If such a tool is already a part of your tech stack, you may want use the preview feature as well. Here are a couple of examples. 

HubSpot

HubSpot is a CRM platform that features email marketing, sales, and help desk services. It has an email preview tool built into the email editor. 

Source

In HubSpot, you can select from around 30 email clients (although this includes different versions of the same email client) and see how your template will look in each of them. They include the most popular email services, such as Gmail, Outlook, Office 365, Apple Mail, and so on. You will be able to view and manually compare the performance of your template. The email preview tool in HubSpot is powered by Litmus; I’ll talk about this service a bit later in this article.

Campaign Monitor

Campaign Monitor is a popular email marketing and automation tool. It has the inbox preview test in the Unlimited and Premier pricing plans. The test generates screenshots of your template rendered in around 20 popular web, desktop, and mobile email clients.

Source

This test in Campaign Monitor also enables you to click through previews and manually compare them. 

ActiveCampaign, Brevo , and Mailjet (Enterprise version) are among other popular email sending services that have an email client preview feature. Also, Mailchimp has an Inbox Preview as part of their email builder tool. 

If you are using another service for sending emails, then a third-party email testing tool is your best choice. 

How to choose the right email client testing tool

Check a streamlined guide to help you select an email client testing based on your technical needs, goals, and budget. 

• Previewing vs. code analysis: As discuss earlier, understand the difference between previewing emails and analyzing email code. Previewing focuses on visual accuracy, while code analysis targets the structure and compatibility of your HTML/CSS. Choose the approach that best suits your specific needs, but I’d always vote for code analysis for more accurate and predictable results.

• Integration with existing tools: Look for email client testing tools that integrate seamlessly with your existing email marketing platforms or development environments.

• Automation capabilities: If you send high volumes of emails or work in an Agile environment, tools that offer automation and continuous integration features can save time and effort. (Email Sandbox is among the few tools that offer automation of all testing flows)

• Support and documentation: Consider the level of support and available resources, such as tutorials and community forums, to ensure you can resolve any issues quickly.

• Cost efficiency: While powerful, email preview tools can be expensive. Assess the frequency of your testing and the number of iterations required to justify the investment. For instance, testing 10 templates across 30 clients with 5 iterations each could lead to 1,500 previews—a significant cost with premium tools. 

• Marketing campaigns: If you rely on email marketing software with built-in template editors and preview features, start there. These tools often come with pre-tested, optimized templates, minimizing the need for additional testing.

• Custom templates: If you’re coding your own templates, prioritize tools that offer real screenshots and manual inspection capabilities. These tools allow you to preview your email across various clients and devices to catch potential errors.

How to test emails in different email clients

Here, I’m covering detailed email testing/preview flows. I start with Email Sandbox, which is a full on sandbox with previews and HTML checks, then I move to Litmus and other purely preview tools. 

Disclaimer: The following sections contain feature lists and pricing references. These were valid at the time of writing but could be subject to change by the time you’re reading the article. 

Email Sandbox

Email Sandbox is a safe environment to inspect and debug emails in staging without spamming your recipients. 

Pricing:

• Email Sandbox has a free forever plan (up to 100 emails a month)
• Paid plans start with the Individual at $14.99 per month

The email testing workflow with Email Sandbox

Step #1

Create a free account, then compose an email and send it to your sandbox. You can do this via your app that supports SMTP authentication, an MTA, or any email sending tool using the fake email address for testing.

Step #2

In the dashboard, navigate to Sandboxes > Projects > My Inbox and find the email you sent. 

Note: You can rename the inbox to your liking and get more inboxes with higher plans. 

Step #3

There are three tabs related to HTML code: 

1. HTML (HTML preview rendered in a web browser) 
2. HTML Source (the HTML code of your email)
3. HTML Check 

Go to the HTML Check tab. Select email clients and device types that are important for you, or check out the whole report and inspect all errors found. 

You can see the support top email clients have for the HTML/CSS used in your emails. The overall report score is displayed as Market Support percentage —  the level of HTML/CSS support across popular email clients. 

Under the overall score, the report is further divided into sections, with each containing:

• HTML element/CSS rule name (for example, :hover, <style> element, margin, etc)
• Email clients that don’t support or just partially support it
• Links to code lines in your email’s HTML where the element/rule was found (redirects you to the HTML Source tab where you can see the entire email HTML code)

Click the “Show more” link to reveal a section explaining what’s wrong and which versions of each email client show the error. 

Based on this data, you will have insight into how many of your recipients will see the email you crafted exactly as you intended.  Better yet, you’ll know exactly which lines of code to fix to improve the performance of your emails.

Besides the HTML Check, Email Sandbox also provides:

• Spam score check 
• Email previews 
• Email headers information
• Blacklist reports 
• User management 
• SSO 
• API
• Ready-to-use integrations for 20+ different languages

Litmus

Litmus defines email preview as an individual screenshot from an email client or device. It offers previews for 90+ email clients (this number includes different versions and devices). There are both the most popular clients, such as Gmail, Outlook, Apple Mail, and Yahoo, and the less used Comcast, freenet.de, and web.de. 

Pricing

• 7-day free trial available on all plans, but no free plan
• Three pricing plans starting with Individuals [Litmus Basic] at $99

The email testing workflow in Litmus 

Step #1

Add a template to Litmus by:

1. Sending it using your Litmus testing email address 
2. Uploading an HTML template
3. Creating a new one in Litmus builder with their template library or from scratch 

Tip: You can check a web preview while working on your template.  

Step #2

Switch to email client previews and select the email clients you want to test to get a list of generated previews. Look at each preview to see whether something is wrong. 

The HTML template for this test was taken from Really Good Emails. 

Tip: For example, Apple Mail 13 and Apple Mail 13 Dark mode are counted as different email clients, and each time you make changes to your template and apply them, the new previews are produced. You should be careful with the email client selection —  otherwise, the preview limit will be reached very soon. 

Step #3

If there’s an issue, click on the email client’s screenshot to take a closer look.  Then, manually check whether the issue is reproduced in other clients and/or devices. 

There may be a flag leading to an article that lists the issues in specific email clients and ways to fix them. Then, you can amend your HTML template right in the Litmus builder and see the refreshed previews. 

Step #4

Once done, push the template to the Checklist. There, you will find the list of newly generated previews, will be able to scroll through them, and select the specific client for additional checks. 

Important Notes: 

• Litmus previews are generated using raw HTML. It means that Litmus can’t guarantee that your email will look exactly the same in an email client.  
• You can share previews via a link or by downloading them as zipped screenshots or HTML content. 

In addition to previews, the pre-sending checklist includes the following tests:

1. The subject line and preview text of your message check across popular email clients. 
2. Accessibility test against six best practices (alignment, alt text, content type, headings structure, etc.). 
3. Links validation. Litmus checks whether links are working and shows their destination in one table. 
4. Tracking check. Litmus checks your HTML code for tracking pixels and, if none are found, will prompt you to add its own email analytics. 
5. Image-blocking check that allows previewing a message with images off.
6. Loading speed check shows how long it takes for your images to load. 
7. Spam test searches for issues that can prevent your emails from landing in the inbox. This check is available in the Plus and Enterprise plans.

Email on Acid

Email on Acid is a popular Litmus alternative that also offers previews in numerous email clients and email campaign precheck. With Email on Acid, you also can preview your email in 90+ email clients (available on Chrome and Firefox browsers). 

Pricing

• All Email on Acid plans offer a free trial, but there’s no free plan. 
• The Basics plan starts at $75 and includes unlimited previews for one user. 

The email testing workflow in Email on Acid

Step #1

Start by selecting the email testing tool from the menu. It offers email preview and spam tests for an HTML template. You can copy-paste, upload, or send it to the Email on Acid testing address.

After pasting the HTML code, you get an Email Test Summary, demonstrating previews for all selected mobile, web, and desktop clients. 

The HTML template for this test was taken from Really Good Emails. 

Step #2

Manually check whether the template looks fine in every client. At first glace, it’s clear that there are rendering issues with the template I used in the example above.  

So it pays to open each preview and scroll top to bottom, to see how it affect the entire template. When you open a preview, you can switch between a visual render and a code analysis summary. The latter has three tabs:

• Code Analysis – shows whether any errors are found.
• Tips and Tricks – a list of issues (no support for animated GIFs for Outlook on desktop, for instance).
• FAQs – recommendations on how to fix possible issues for a specific client.

Tip: For an extra $75, you will be able to submit your template for code repair. 

Step #3

After reviewing the test results, fix the HTML email template and create a new test. Iterate until you are completely happy with the results.  

Tip: You can also share email preview results via a link. 

Aside from the email testing functionality, Email on Acid also offers:

• Campaign precheck, a promoted set of tests that includes email preview in 90+ email clients, preheader text preview, accessibility guidelines compliance, spam and domain block tests, URLs validation, spelling check, and image optimization. This checklist is similar to Litmus features. 
• Email editor for creating a new email template project. You can upload a template as a ZIP file or from a URL, select a template from their library, or by entering or pasting your HTML code. You will see how your HTML renders and also will be able to generate previews in selected email clients. 
• Spam testing to analyze the email sender. It can be performed in a few ways —  send a test email from your ESP to a provided seed list or use your SMTP server to send a test. Email on Acid will analyze email server reputation and configuration, email content and subject line, and the IP block list. 
• Optimizer for improving your HTML template right away. Enter your HTML code and instantly receive the modified version with a list of suggestions and validation results.
• Analytics for tracking engagement, subscriber, click activities, and benchmarking diagnostics. 

Email Preview Services

Email Preview Services offers real-time and real-device screenshots for 60+ email clients. It also provides email analytics, inbox and spam testing, and an email editor. On the Enterprise plan, its functionality can be accessed via a white-label API. 

Pricing:

• All Email Preview Services plans offer a 7-day free trial, but there’s no free plan. 
• Paid plans start with the Standard at $25 a month.

The email testing workflow in Email Preview Services

Here, I won’t be taking the step-by-step approach because there aren’t really any steps. Basically, everything happens in one flow, and here’s what to do.  

Go to Previews and add your HTML code. If you don’t have it, you can build a new template with a drag-and-drop email editor. Alternatively, you can generate a test email address on emailpreviewservices.com and send a message from your ESP or email client. 

After running the test, you see a list of screenshots showing how your email template looks in each of the selected email clients. You don’t receive any code analysis or tips on what should be fixed. If something doesn’t work for specific email clients, you should edit the template and run another test. (Email Preview Services offers version tests though). 

The HTML template for this test was taken from Really Good Emails. 

In addition to email previews and the editor, you can track recipients’ activity with Analytics and run spam tests. The spam test includes sender IP reputation, spam filters, email providers delivery report, headers preview, and content analysis. 

Wrapping up

Now, you should be ready for an email client testing marathon. The important thing to keep in mind is whether you want preview + code inspection or just a preview with gazillion different clients. 

I’ll repeat myself, but my recommendation is always to focus on code inspection and check the support for different devices and clients. So why wait, try Email Sandbox. 🙂