• Nikhila Jain

The 5 Best Email Subject Line Testers to Increase Your Open Rates

How many emails do you get daily? Lemme guess near about hundreds…

And out of these, how many do you open? Maybe a few, say 10 or 20….nearly 80% of emails remain unread.


As a copywriter, you know that email marketing is one of the core components that you work on that helps your customer attracting leads, promote products & services, or offer discounts that generates sales. And hence, it becomes vital that your email stands out and compels the reader to click and open it. Even if you have enticing content to hook your readers, but that content has no meaning if your email is never opened. And that is when subject lines play their vital role. They create an association between your brand and the subject of the email. This association helps you establish trust and credibility with the person on the other end of the line, and it encourages them to click and read the content.


Why you need a catchy Subject line?

The subject line of your email is often the first impression a user gets from your email. If you want to get a response from someone, make it easy for them by writing subject lines that are memorable and enticing. The subject line can also act as a hook—and a way to build trust—for opening an email. People are more likely to engage with emails that have a clearly defined subject line.

Thus, it is significant for you as a copywriter to spend ample time creating those unique and enticing subject lines.

So, say you spent hours creating the subject line that you think will work, but you have no means to visualise how the subject line will behave once landed in your intended user’s account, and that’s where the subject line testers are our saviours.

I recommend these five email subject line testers that every copywriter should use to improve your emails open rate.

Omnisend Subject Line Tester

Omnisend subject line tester evaluates your subject line on a number of parameters like Character count, Word count, Helpful words, Negative words, Spam alerts and more. Based on these criteria, it scores the subject line in a range from zero% to 100%. It provides helpful suggestions in terms of suggestive positive words that you can use to make your subject line more impactful.

✓ Free tool - It is a free tool, and you can test it over and over again.

✓ Preview - It lets you see how your subject line looks on a desktop as well as on mobile.


Like Omnisend, SubjectLine.com also scores your subject line in a range from zero to 100 points. It offers detailed information on the recommendations that you can apply and improve your subject line. It checks the subject line across 800 rules and data gathered from over billions of messages. It also points out the issues that could eventually land your email in a spam folder.

✓ Free tool - It is a free tool.

✓ What is right - It tells you what you have done correctly, and you know what to keep and what needs modification?

Mizy’s Email Subject Line Tester

Mizy’s an AI-powered email subject line tester that evaluates your subject line against the data gathered and techniques like deep learning and machine learning. Like other tools, it also scores your subject line on a 100 point scale. It also provides recommendations that will help you improve your subject line.

✓ Free tool - It is a free tool.

✓ Continuous scan - It continuously scans and analyses thousands of email campaigns and concludes what works and what doesn’t, so all you have to do is focus on what hasn’t worked.


Nowadays, almost every other person accesses their emails on mobiles, and thus it becomes imperative that you visualise how your email subject line will look on their device. TestSubject does exactly that for you. It simulates how your subject line will look on various mobile devices and lets you take calculative decisions to make changes.

✓ Free tool - It is a free tool.

✓ Multiple devices - It lets you visualise on different devices like iPhone 6, 6s, Samsung Galaxy Note 5 etc.


Like other tools, it also provides a score on a 100 point scale and evaluates your subject line on a number of parameters like readability, length, and spam alerts. It also lets you preview on a desktop and mobile mode for better visualisation.

✓ Free tool - It is a free tool.

✓ Sentiment analysis - It provides a great feature of sentiment analysis with a wide range of marketing emails and scores your subject line on negative, neutral or positive sentiments so that you can tweak what is needed.

Being a copywriter or a marketing professional, creating catchy subject lines might look tricky and effort-intensive on the onset. These handy tools will let your creative juices flow and enable you to write those enticing subject lines that will ultimately increase your email open rates.

I hope these tools will make your life easy as they have made mine....

Happy Copywriting!

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