how to write a great email subject line

How to Write a Great Promotional Email Subject Line

Promotional emails flood our inboxes daily. How do individuals decide which ones to open?

We see dozens of promotional emails flood our inboxes on a daily basis, but very few people have the desire or patience to read every single email. Individuals will cherrypick emails to open, largely based upon brands they love, or with whom they do regular business. It may be up to a creative subject line to entice the customer to open.

Every email marketer has undoubtedly been faced with the daunting task of writing subject lines for corporate promotional emails. If the marketer is on top of her game, she will test multiple subject lines for each email to find the most effective one, then send the bulk of the list the winner.

But where to start? And what makes a subject line stand out in the inbox? What can you possibly say to get someone to open an email that they otherwise would have discarded?

It depends on your business and subscriber list. A company that provides medical screenings to the elderly will have entirely different guidelines for subject lines than a company that sells headwear to skateboarders. The former’s customers expect a gentle tone, while the latter’s customers expect in-your-face edginess.

Which email subject line would receive the most opens?

Consider this scenario. A health insurance company is emailing their list, hoping their subscribers take note and monitor their blood pressure. Kim is in charge of deploying the email and writing the subject line, and really wants to impress her manager. She has come up with five ideas to test to her audience. Which of her subject line ideas do you believe would result in the highest open rate?

  1. Be mindful of your blood pressure this month
  2. Low blood pressure = healthy living!
  3. (NAME), is your blood pressure too high?
  4. 3 simple ways to lower your blood pressure
  5. Hey, Fuckface! Death looms. Beware…☠️☠️

#1 and #2 would probably perform poorly. There’s little if any incentive to open. If you’re interested in monitoring your blood pressure, you’ll do it on your own time.

#3 is personalized with the customer’s first name, giving the impression that the insurance company cares about each customer. (It will also trick some older subscribers into believing this is a personally written email!) It also poses a question, which puts the idea into the subscriber’s head that maybe they are unwell.

#4 would perform adequately, stating that this will be a very brief but helpful email, and very actionable. Everyone has time to read three bulletpoints that could save their lives.

#5, without a shred of doubt, would result in the highest open rate in a landslide! But people would be opening it for the wrong reasons—terror and rage. Few would even bother to take the medical advice after being called the F-word by their insurance company. Unsubscribe rates would go through the roof, and your customer service line would be floored with cancellations. But the open rates would set records!

Basic tips for writing a good subject line

A good tip to remember when writing subject lines is this: you are not your audience. You, as an email marketer, are likely smart, clever, witty, and a good writer. What you find shrewd may fall flat on your readers. In order to market to them, you have to think like them. Additionally…

  • Keep it around 35 characters. You don’t want it to be too long and have words get cut off. A good rule of thumb is just to simplify. You don’t need to give the full terms & conditions in the subject line.
  • Pique the customer’s interest. Perhaps instead of saying “25% Off Pants: Today Only!” you could say “See what’s 25% off today only!” The curious customer will click just to find out, then get sucked in and buy something!
  • Some personalization is good. If you have your customer’s name, it’s fun to throw it into the subject line once in a while. Instead of “25% Off Pants Today Only” you could say “Bobby, Take 25% Off Pants Today Only!” Worth a test anyway!
  • Emojis and symbols are also great, if used sparingly. Find a full list of emojis here. These symbols are also widely acceptable across all email platforms.
  • Creativity generally beats out to-the-point subject lines, to an extent. Getting too cutesy gets annoying to a customer. Try plays on words, puns, and some silliness without it becoming too regular.
  • Seasonal and holiday-themed subject lines are generally well-regarded, but be more creative than “Spooktacular” for Halloween and “Eggstravaganza” for Easter.
  • Above all, simply knowing your audience and what they want is the most important. Does your audience generally want to save money? Want to be the first to own your new product? Want to earn a reward? Want to learn some inside info? Knowing this and catering to their motives is key.

My Hot Take

I am an email marketer by trade. I have spent the better part of the 2010s managing email programs for major companies in a variety of fields, from sports equipment to security systems to exclusive clubs. I undoubtedly have written tens of thousands of subject lines, and I can say without a doubt that including the customer’s account number in the subject line is the very best way to get opens. An email with the subject line of “Save 15% this weekend only” will see a dramatic increase in open rate if you change it to “Account #0011035: Save 15% this weekend only”. It suddenly looks very personal, and also more official than using the customer’s name! In time you will simply know what works and what doesn’t.


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