The Beginner's Guide to Email Subject Lines

Email is one of the most budget-friendly marketing tactics available to small businesses, but it is only effective when the audience clicks and reads. With 33% of email recipients stating that they’re influenced by email subject lines, why not focus on making those subject lines compelling?

The power of email subject lines

The subject line of your email is your first impression on recipients. Its importance is similar to the first few words inside a Facebook caption, or the introductory chapter to a novel. It’s the virtual equivalent of a door knock. When done right, email subject lines can get your audience to stop what they’re doing and engage with your content.

Deciding on key performance indicators (KPIs)

If you’re sending multiple emails and using subject line variations, how do you know which are succeeding—and which aren’t? The answer lies in knowing what key performance indicators (KPIs) to measure to determine your email marketing return on investment (ROI). Depending on your business goals, certain KPIs will serve as a better measure of success than others.

The following KPIs commonly reflect recipient engagement and the overall performance of an email campaign.

  • Open rate: The open rate is calculated by dividing the number of emails opened by the number of emails sent, then multiplying the answer by 100. So if you send 10 emails, and only two are opened, your open rate is 20 percent. As per Experian’s benchmark report, the average email open rate was 25% across all industries. An open rate below 25% suggests that your email subject lines aren’t performing well. Try different variations to see what resonates with your audience.
  • Click-through rate (CTR): CTR is calculated by dividing the number of clicks within opened emails by the number of emails sent, then multiplying the answer by 100. According to Econsultancy’s email marketing benchmark guide, the CTR averaged 3.42% across all sectors. A CTR above 3.42% means people are opening your emails and responding to your call-to-action. Small businesses with a low CTR should experiment with different subject lines and call-to-actions to see what variation generates the most clicks.
  • Spam complaint rate: You get it by dividing the total number of spam complaints by the total number of emails sent, then multiplying the answer by 100. Your spam complaint rate should be lower than 0.1% at any given point. That equals 1 spam complaint per 1,000 emails sent. If you’re experiencing a high spam complaint rate, it could mean that your subject lines are coming off as spammy to your recipients. The solution is to make them personal and compelling.

Email subject line tactics that work

Spending some extra time crafting your email subject lines can help you increase open rates, get more clicks, and avoid the spam folder. Use the following strategies to give your emails an edge.


Personalizing your subject lines is a great way to get your emails opened, and it can be as simple as using the first and last name of the recipient. PeoplePerHour and do a great job at addressing people by their first names. You can also weave in birth dates, locations, and other personal data to pack a stronger punch. Small businesses that take this route can save time by setting up an email series (multiple email messages that will be sent to people on a schedule automatically) with personalized subject lines through their email service provider.


Play up the utility card first before using sales-oriented communication. Showcasing exactly what value the email offers is a powerful way to stand out in a cluttered inbox. As an example, the subject line “Top 10 Spas in the US” gives an indication that the email is resourceful, and is likely to appeal to those interested in spa services.

Action verbs

These are call-to-action words that are intended to trigger a specific action. For instance “Sign up to Receive Invites for Our Calendar Event” is likely to be more effective than “Our Calendar Event is Going to Be Exciting”— if you are trying to drive people to your event. Action verbs like “sign up,” “enroll,” and “download” create a sense of urgency and curiosity, prompting recipients to check out your offer.


Dressing up your email subject lines with emojis is a unique way to grab people’s attention. A contextually relevant emoji can add great value to your subject line, which will boost your open rate. However, emojis should be used purposefully. If your subject line is about a discount, add a smiley face with sunglasses or hearts. If the subject line is serious—for instance, something related to loss of customer data—skip emojis altogether.

Tips to get past email spam filters

First things first: your email needs to actually make it to the reader’s inbox before it can be effective. While it’s understandable why some emails are immediately marked as spam, a few seemingly innocuous practices can also trigger the journey to the scrap heap. Follow these tips to ensure your emails don’t get knocked back by the bots.

  • Avoid using ALL CAPS as it gives an illusion that you’re shouting at the reader.
  • Avoid excessive usage of asterisks and punctuation as they can make your subject line appear unprofessional.
  • Avoid words that are known to flag spam triggers, such as “free offer,” “lotto winner,” and “save $.” Here’s a detailed list of common spam words.
  • Don’t send emails with one-word subject lines. They don’t convey value.
  • Don’t trick recipients by using “fwd:” or “re:” at the start of your email subject lines to suggest ongoing communication.

Use these guidelines to ensure your emails steer clear of spam filters.

Final thoughts on email subject lines

Appeal to your recipients with enticing subject lines that communicate value, and your emails will be opened. Your open rate and click-through rate should soar, and your spam complaint rate decline, once you integrate these tips into your email marketing strategy.

The Beginner's Guide to Email Subject Lines

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