You Can Use These 3 Email Subject Line Tester Tools

Do you have a problem with low email open rates? Updating the subject lines is a good idea.

The average email open rate across all sectors was 21.33 percent, according to Mailchimp. If your open rate is low, it’s typically due to a combination of these three factors:

The audience/segment you emailed did not match the message’s content.

Your email sending schedule isn’t in sync with your target audience.

The receiver will not be interested in your subject line.

Taking a Look at Email Benchmarks

When it comes to subject lines, the most important metric they affect is your open rate. Since the subject line and sample text are the first things a recipient sees, it’s only normal that they have an impact on whether or not they open your email.

The average email open rate was 21.33 percent across all industries. (Image courtesy of Mailchimp)

  • a company
  • Level of Openness
  • Click-through-rate
  • Bounce Hard
  • Bounce Softly
  • Level of Unsubscribe

Purchasing Real Estate

  • 19.17 percentage point
  • 1.77 percentage point
  • 0.38 percentage point
  • 0.56 percentage point
  • 0.27 percentage point


Work on the building

  • 21.77 percentage point
  • 2.26 percentage point
  • 0.86 percentage point
  • 1.28 percentage point
  • 0.39 percentage point


Services/Agency for Creatives

  • 21.39 percentage point
  • 2.66 percentage point
  • 0.58 percentage point
  • 0.93 percentage point
  • 0.35 percentage point


Dental & Medical Treatment

  • 21.72 percentage point
  • 2.49 percentage point
  • 0.51 percentage point
  • 0.63 percentage point
  • 0.28 percentage point


Services for Professionals

  • 21.94 percentage point
  • 2.55 percentage point
  • 0.56 percentage point
  • 0.83 percentage point
  • 0.31 percentage point


Checkers for Favorite Subject Lines

Stop. Sending. Emails. With. Bad. Subject. Lines. Say it loudly for the people in the back: Stop. Sending. Emails. With. Bad. Subject. Lines.

Your subject line is the face of your email; it is what everyone sees first and uses to decide whether or not to open it. Plus, Gmail and other sites are checking your subject line for potential SPAM or phishing long before it enters your audience’s inboxes.

In a nutshell, your email subject line should represent the substance of your email, pique the audience’s attention, and avoid terms that would be blocked by email clients.

There’s also no need to send emails with poor subject lines when there are some fantastic (FREE) resources available to review them. Let’s go over it again!

First, send a check.

At SimpSocial, this is a personal favorite. The interface is simple to use, and the recommendations are simple to enforce and resubmit for review. lets you test your emails (with emojis!).

Not long ago, someone at SimpSocial had a win with a score that seemed to deliver! The open rate of the email with this subject line was 29.6%.


A+ for the Submit Check It Subject Line |SimpSocial

SubjectLine.Com is number two. claims to have checked over 10 million subject lines, and their rating system is simple to understand and use.

Fun fact: on, the same subject line that did well on Send Check It got just 64/100 points! We assume that the feedback is 100 percent accurate and that using it is a smart idea. However, score isn’t all, and each subject line tester’s parameters vary slightly.

CoSchedule is the third choice.

Another SimpSocial favorite is CoSchedule’s free email subject checker. We’re not shocked that they have such a comprehensive subject line grading tool as an enterprise-grade content marketing tool.


Screenshot of the CoSchedule Subject Line Checker | SimpSocial

We like how CoSchedule goes a step further with helpful word banks that suggest alternative terms to increase your open rates. We really like how this tool provides inbox previews of your subject line to indicate where the characters are likely to truncate.

What is the most effective subject line?

There isn’t likely to be a “best” one. We prefer subject line testers who have actionable advice and submit several times until the score is perfect. The same subject line earned three very different scores across our favorites, as illustrated, but the end result was an email with a higher-than-industry-average open pace.

Email subject line best practices will continue to change, but when you match your subject line with the content within and your audience’s preferences, a subject line tool can be a valuable ally in the battle to increase open rates!

No leads were lost. reduced overhead.
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