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Best Email Subject Line Testing Tips To Get More Email Opens

Did you know that the average person receives over 100 emails every day? Getting your email delivered to the right person is only half the battle – the real challenge lies in standing out from the crowd. And it starts with testing your email subject line to assess essential elements such as deliverability, length, clarity, tone, and other factors that influence the reader’s decision to open the email.

The subject line is considered the most important part of an email. This does not mean that other routinely scrutinized email campaign elements (such as the objectives and message body) are not important. The subject line influences the recipient’s decision and determines whether they’ll open or discard your email. A good subject line briefly highlights the contents of the email, addresses the recipient personally, and gives them a reason to open your email.

But, creating a convincing email subject line takes much more than just creativity. Deeper insights gathered with subject line testing can help paint a clear picture of your email campaign performance. In this post, we’ll highlight our top subject line testing best practices tips that are guaranteed to generate impressive results in your next campaign.

What Is Email Subject Line Testing and Why Is It Valuable?

The subject line is the first line of text that readers see when they open your email. On most email marketing software, the subject line is located below the CC field, labeled as “Subject.” The subject line’s core purpose is to grab the reader’s attention, pique their interest, and encourage them to read the email’s contents.

Campaign managers check the subject line for:

  • Reception
  • Optimum length (measured in characters)
  • Quality
  • Click potential
  • Open rate potential

Subject line testing is vital to the performance of an email campaign. It sheds light on the potential conversion rates, CTR, and open rates. Subject line testing also reveals flaws in your email subject line and pinpoints the key areas for improvement.

Types of Testing For Email Marketing

As an email marketer, you’re well aware that the rules of engagement with your audience and the campaign testing rules aren’t engraved in stone. There exists different ways to test subject line; we’ve outlined the most effective approaches – A/B testing and Split testing.

A\B Testing For Subject Line

A/B testing can be done by sending out two variations of the same email with varying subject lines to two random recipient groups. Group A receives the original subject line, while group B receives a variation of the first subject line. For a few days, the campaign manager will await the results and analyze the outcome to identify the highest-performing subject line.

In our case below, pretend that you’re a Marketing Event Organizer inviting marketing professionals from your email list to share their expertise in an annual webinar.

  • Email subject line for group A: “You are invited to join the annual marketers’ webinar.”
  • Email subject line for group B: “Hone your marketing skills in the annual marketers’ webinar.”

The highly-performing subject line test ideas will be spotted by comparing their CTRs, open rates, and conversion rates. There isn’t one right or wrong way to design your template; it depends on the audience, brand style, and product/service, among other variables.

Split Testing

In split testing, the campaign manager selects a section of the subscribers’ list for testing and creates several variations of a subject line. The winning subject line is what will be used in addressing the remaining section of the database.

Here’s an example of a split test for email subject lines based on our previous case study:

  • Sample email subject line 1: “[First name], you’re invited!
  • Sample email subject line 2: “[First name], join us for the annual marketers’ webinar, [date], [venue]
  • Sample email subject line 3: “Invest in your career! Register for our annual marketer’s webinar.”
  • Sample email subject line 4: “Free tickets to the [event organizer] annual marketer’s webinar!”
  • Sample email subject line 5: “Don’t miss out on the [year] marketer’s webinar.”

These test email subject line cases will yield different results. For instance, subject line 1 may receive a 16% open rate, while the less personalized subject line 5 generates a lower 10% open rate. The best variant can be used to address the remaining subscribers.

In any case, testing with a larger sample guarantees more accurate results. Email marketing tools such as Atompark’s Atomic Mail Sender can help you reach an almost limitless audience segment and gather deeper insights into your audience’s patterns for future reference.

How to Provide Subject Line Testing For a Better Result

Continuous email marketing subject line testing lays the foundation for predictable results in future campaigns. It sets the pace for consistent improvement in the key performance indicators. Below are solid tips to help generate better results for your campaign:

Make Sure Your “From” Line Is Clearly Recognized

Trust is key in email marketing since nearly half of all recipients will open an email depending on who it’s from. Recipients are more cautious than ever when it comes to their email security, thanks to the rising phishing attacks dominating the email space.

As such, we recommend using the company name on the “from” line to demonstrate your trustworthiness. For example;

mary@companyname.com looks and sounds more trustworthy than mary9817@gmail.com.

Optionally, include the company and your role, followed by your name. Other times, your name or the company name will suffice. The idea is to get recognized easily by the recipient.

Preview Text and Subject Line Should Be Partners

The preview text and the subject lines are two sides of the same coin. The preview text complements your subject line by providing more context to the email’s message. It appears next to the subject line with the objective of retaining the reader’s attention.

A good preview text should be short and straight to the point. It should be compelling from the start. For instance, you could test your subject line after adding a CTA to the preview text.

Learn Your Audience

Testing your email subject lines offers front-row seats to your audience’s traits, preferences, responses, and behavior while engaging with your emails. What works for one test group may not necessarily work for another.

For instance, a short subject line (less than 41 characters or 7 words) can generate higher open rates for a B2B audience of busy professionals that skim through the text.

Update Subject Lines For Non-Openers

At some point in the future, you will notice that your current subject lines are not getting the results that you were hoping for, which is quite normal in marketing. In fact, 

only 17 out of 100 emails get opened on average but that number can be raised by swapping redundant, spammy subject lines with fresh, catchy ones.


Some tools have a resend feature where you get the opportunity to check the email subject line, alter it, and resend it to the same recipients. On other email marketing software, you need to do this manually by rewriting the subject line and sending a new email to the old audience who did not open the email the first time.

Brainstorm Fresh Subject Line Ideas

While coming up with fresh subject line ideas is not easy, repurposing old subject lines has its limits. Your recipients probably don’t want to engage with outdated subject lines or, worse, get bombarded with spammy, generic emails.

You can write down 10 experimental subject line testing ideas to expand your creativity and keep your audience engaged. The best subject lines take into account the customer’s needs, brand consistency, and the campaign’s objectives, at the very least.

Play With Personalization In Email Subject Line

Personalized emails have significantly higher open rates. Personalization makes the subject line more relevant to the reader by including their name, occupation, company, or other personal detail that they can relate to.

Try Numbers

A number present in email subject lines can exponentially increase email open rates. Numbers work by demonstrating a clear degree of certainty in your offer and predictable and measurable results. In essence, they display at a glance the tangible value that your recipient will get by opening the email.

Adding Emojis

Never underestimate the power of a well-thought-out emoji strategically incised into your email subject lines. As it stands, 92% of the online population uses emojis to express their feelings in their daily interactions. Using emojis to spark emotional responses in your email subject lines can help generate higher open rates.

Never Stop Testing

Testing subject lines is a continuous learning experience because many variables go into successful email subject lines. These variables include:

  • Seasons
  • Industry
  • Urgency
  • Company/brand style
  • Length
  • Relevance

The list goes on. Keep experimenting with fresh subject line ideas, new target segments, and new goals. Gather as much information as you can, with the objective of understanding why your audience will or will not open your email. This information makes it much easier to tweak your email marketing campaign for higher email opens.

Final Words

Learning how to test email subject lines is just the beginning of a successful email campaign. However, if you’re looking to go expand your reach to hundreds or even thousands of potential customers at a go, Atompark’s Atomic Mail Sender is what you need. With this tool, you can tap into the power of personalized emails and target over 200,000 recipients in one go.

Ready to see how it works? Download and try the Atomic Mail Sender for free today!

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