Feb 22, 2023

14 Subject Line Tester Tools To Boost Your Email Open Rate

Email open rate is the number of clicks an email receives divided by the number of emails sent. With that in mind, it's important to know how you can improve your open rate in order to increase your email response rates.

Email open rate is a metric that comes up in many conversations about marketing campaigns, and you may be wondering how to increase it.

We’ve got some great tips for you

The Tricks

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  • First, pick a subject line that grabs your reader’s attention. Subject lines are the most important part of an email—they’re the first thing people see when they open a message, so they can decide whether they want to read on or not. Try shortening your subject lines and testing them out with real people. You might find that some subjects work better than others!

  • Second, use visual cues in your subject lines. Many marketers have found success by using images in their subject lines instead of text alone (you can even use images from Instagram if that’s more your style). It’ll help make your emails more engaging for readers who are interested in seeing images before reading text—which is exactly what you want since this is where your business needs growth.

  • Finally, be sure to include a call-to-action (CTA) at the end of every email! This will encourage people to click through from their inboxes into whatever site or app you have advertised in the body of the email itself (like this one!).

The good news is that there are a number of tools you can use to boost your email open rate based on subject line. You can use the tools to make your email subject line better once you've mastered the fundamentals of doing so. You can benefit from these in a number of different ways.

The overall strength of your writing can be graded using a variety of approaches, first.

These tools often compare the subject line of your email to a database of millions of actual email subject lines. The programme then compares your subject line to previously successful subject lines that are similar to yours and forecasts your likelihood of success based on the latter.

Additionally, there is subject line tester software that may estimate the likelihood that your emails will be classified as spam based on their subject lines. This programme can prevent you from being flagged as a spam sender by ISPs, which would severely harm your future email marketing initiatives.

Tools to boost your email open rate 

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Email subject line grader

One of several simplest Subject line testing tools available is this one. Your subject line's appeal to your prospects is evaluated by the tool based on a variety of parameters. All you have to do is enter your subject line into the tab, and it will provide an opinion based on the subject line's kind and a general evaluation:

  • Mixture of words and balance

  • words used

  • number of characters

  • power phrases

Headline Analyzer

When it comes to subject line testing, the Coschedule Headline Analyzer tool is one of the essentials. Even though the tool was designed for headlines for articles and blogs, it serves our objective of testing email subject lines just as well. It is a helpful tool for writing effective subject lines because it provides an overall evaluation as well as recommendations for how the article can be strengthened in terms of structure, grammar, and word choice.


When it comes to subject line testing, Subjectline.com, this tool aids marketers with topic line testing. Over a billion emails sent and tracked by subjectline.com's partners and clients were used to get the results. It assesses marketing and performance-related issues, as well as any filtering and deliverability problems.

EMV Analyzer

About 20% of the words in the English language have emotional marketing value (EMV). These are words that appeal to the readers' intelligence, empathy, or spiritual side. Based on the EMV, this tool analyses your subject line.

Email Subject Line Tester

You can use the effective and user-friendly tool Email Subject Line Tester to see if the words in your subject lines are considered spam. The programme evaluates a number of factors, including reading comprehension, sentiment, and customization, and provides you with a score out of 100 from which you may choose whether to use or modify the sentence.


This tool makes sure that your subject lines don't contain any trigger words that could cause one of the filters employed by your prospects to flag it as spam. The last thing you want is for your mail to be deleted because spam filters mistakenly thought it was spam after spending so much time and effort on it.

Hemingway App

Ernest Hemingway was renowned for his uncomplicated writing. Shakespeare's "The Lady doth complain too much" might be translated as "She is opposing it vehemently" in an Ernest Hemingway book. That is what the tool does. It examines how a middle-level human interprets your topic line.


According to Mizy, it approaches topic lines in a unique way. Mizy employs AI and deep learning, in contrast to other subject line testers, to assist you in finding the ideal email subject line. Additionally, Mizy has access to an email database and is aware of the open and click-through rates of each email.

Mizy's deep learning neural network makes this possible. It has the capacity to gather information and reorganise itself in order to deliver more beneficial insights on what is and isn't producing the best email results. After you submit your subject line, Mizy will produce an overall performance score (out of 100) and offer suggestions for how to make your copy stronger.


A virtual subject line testing platform is called Touchstone. With a database of more than 21 billion emails, you may test subject lines. Results are displayed as a percentage, showing how well your subject line would do in comparison to subject lines for emails in your industry that were comparable. In order to locate the best version as quickly as possible, you can test up to 10 subject lines at once.

Send Check It

It  is another useful tool that you ought to be aware of. Its claim to fame is that it evaluates and grades your work using 16 different criteria. This implies that when you utilise this tool, you don't just receive an aggregate grade for your email subject line.Additionally, you receive more detailed information on the exact areas in your subject line that should be improved.

This may make it simpler for you to improve subheadlines that need improvement because it offers standards that other checkers do not, such as:

  • Personalization

  • Emojis

  • When the word "free" is present

  • Punctuation


In addition to letting you inspect email bodies and headers (including subject lines), Mailtrap functions as a virtual SMTP server. Mailtrap simulates an actual SMTP server's operations. It eliminates any chance that a test email may end up in the mailbox of a real client by separating staging emailing from production. Because of this, no subscriber will ever unintentionally get spam.By inserting 5 to 10 lines of setup code, Mailtrap organises email from each server to individual inboxes. At Mailtrap, developers link every server to a specific mailbox. It is simple to test staging emails because all emails from that server will be kept in a single inbox.


Based on well-established analysis technology created by the Advanced Marketing Institute, this free email tool will look at your headline to get the Emotional Marketing Value (EMV) score. Successful copywriting involves deeply and emotionally connecting with your readers, and your headline is unquestionably the most crucial piece of content you employ to do this.Your headline will be evaluated and graded according to how many EMV words it contains overall relative to the total amount of words it contains. If your email subject line needs to convey more delicate emotional information, this tool is ideal for you.


Despite being a blog title generator, SEOPressor also has some fantastic suggestions for email subject lines. Enter the keyword and choose from the drop-down menu the category it falls under. Generate titles by clicking the button. There are several options from which to pick. You can use them as inspiration for the subject line of your email. 

Kickass Headline Generator 

A programme that creates catchy headlines, the kickass headline generator may also be used to create free email subject lines. Additionally, this tool differs from the generators discussed above. Here, you won't find ready recommendations. In the tool, you must provide conditions in order to receive formulas. It is then up to you to decide on the format of your subject line or headline and add any other components.


The subject line is the first thing that people see when they open an email. It's also the most important part of your email, as it helps you connect with customers and prospects.



Did you know Email Open Rate is a metric that comes up in many conversations about marketing campaigns, and you may be wondering how to increase it.

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