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Learn actionable email subject line best practices to improve your open rates and engagement. From A/B testing to personalization, we outline our favorite trusted tips to ensure your email marketing efforts translate into results.

Picking the best email subject line is a lot like Indiana Jones knowing which goblet was the Holy Grail in the Last Crusade — you must choose wisely.

In one of our recent posts, we discuss email marketing best practices at a high level. However, it's especially important to discuss the value of email subject lines. HubSpot’s research finds that 35% of email recipients open an email based on the subject line alone. That means spending extra time creating an intriguing subject line can do wonders for your open rates and engagement. To get you started, we assembled five email subject line best practices that will help you write more efficiently, and overall engagement.

Email Subject Line Best Practices

  1. Keep It Short and Sweet
  2. Avoid Traps Like Sales Language and Spam Words
  3. Add Urgency By Including a Deadline
  4. Ask Questions
  5. A/B Test
  6. Personalize
  7. Always Look for Your Next Adventure

Keep It Short and Sweet

Your eCommerce email subject line should be short and memorable. At a glance, it should catch your eye enough to stand out in a crowded inbox. Similarly, it should be intriguing enough for your audience to engage. Keep in mind that most people don’t open every single email they receive. Only the subject lines that really grab the reader’s attention are the ones that will produce results.

You should also consider subject line length. Subject lines that get cut off or are too wordy can ultimately lead to disappointing engagement. We recommend not exceeding 60 characters to improve subject line visibility. You should also keep the mobile experience in mind. If most of your views come from a mobile platform, try to keep the number of characters down to about 35.

Avoid Traps Like Sales Language or Spam Words

Although you may see many businesses use words like “free,” “help,” “percent off” or “reminder” in their subject lines, it’s a trap! Those commonly used words are key spam filter words according to MailChimp, so make sure you avoid them whenever possible. 

We also advise against writing email subject lines in all caps. Although it may seem like a great way to get someone’s attention, this approach can also result in your message getting caught in a spam can. Keep things clear, concise and honest to ensure your message arrives.

Add Urgency By Including a Deadline

We are all busy and sometimes we forget to open emails in our inboxes. Unfortunately, even the most creative of email subject lines can fall victim to this trend. To motivate your readers, try adding a deadline or specific date to create a sense of urgency.

Give your readers a reason to take action and open your email by making it clear that whatever you are offering isn’t available for long. The exclusivity of a limited time offer can also entice your audience. Finally, make your customers feel that they MUST take fast action by including a timeframe of your sale or offer.

Ask Questions

Posing a question in your email subject line is a great way to get someone thinking. If we sent this blog to you in an email with the subject line “Are You Looking to Get More Email Open Rates?" chances are your curiosity to know the answer will likely motivate you to open it.

If you take this route, it is extremely important that you provide a solution to the question you introduce. Failing to do so could cause your contacts to doubt your credibility in the future.

A/B Test

Be adventurous and A/B test your subject lines to figure out what works and what doesn’t. If you’re using HubSpot Enterprise, you should be doing this with nearly every email you send. It's a free and powerful functionality that can increase open rates and drive additional engagement.

Do certain keywords in your subject lines receive higher open rates? Do questions in your subject lines motivate your contacts to act? These are just a few of the questions you can test to make your emails smarter with A/B testing.


Personalizing emails humanizes your messages and helps to engage your contacts. Including your subscriber’s first name lets them know you care and that they are more than just an automated recipient. As a result, they may be more likely to engage with your email content. If you plan to use personalization tokens in your emails, make sure you have adequate fall-backs to avoid email send errors.

Additionally, consider how personalization aligns with your brand. For example, emojis can be useful and enticing tools for more casual businesses. Stay true to your brand and always make sure your content matches your existing personality, voice and tone.

Always Look For Your Next Adventure

Remember that not everyone will find the same tips helpful when it comes to email marketing. If you manage an eCommerce business looking to generate revenue, your email subject line best practices will differ from a B2B business looking to generate leads.

At the end of the day, adventure and data are the hallmarks of successful email marketing efforts. After all, you never know what opportunities you could discover that turn into future marketing success.

Want to learn more about email marketing tips or have a question for our marketing team? Send us a message using the form below!

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