The 5 rules of highly-opened email subject lines

Vector graphic of an envelope with a document poking out of it, symbolizing an open email.

“Use keywords”  “Don’t go over 50 characters” “Start with action oriented verbs” “Use emoji” “NEVER use emoji”

These are just some of the pieces of advice you’ll get when you Google “how to write an email subject line”. In fact, Google returns over 31,000,000 results for that query at the time of writing.

This number makes more sense when you know that one of the most common email marketing metrics is email open rate – which is directly tied to how strong your subject line is, making writing subject lines that get opened a crucial part of your email marketing program.

Unfortunately, many marketers stick to the rules above, which are outdated and restrictive. They offer “do” or “do not” solutions, instead of helping you understand the psychology behind why people open emails.

When you understand the reasons why people open emails to begin with, it becomes very easy to write subject lines which get opened.

Here are five psychology-based principles conversion copywriters use when creating subject lines that get opened:

#1 – Be emotional

Ask any professional salesperson why people buy and they’ll be able to tell you the following: “People buy for emotional reasons.” Email subject lines operate on the same principle. If your subject line incites an emotional response in your reader, they are far more likely to open your email than when reading a more logical subject line.

You can do this by leaving a curiosity gap or by appealing to other emotional triggers, like relevancy, urgency, instant gratification, authority, or fear.

The emotional response here creates an immediate need to know more, which leads to more of your readers clicking “open”. Just make sure that your content matches up with your subject line – misleading subject lines are likely to get you marked as SPAM and unsubscribed from.

#2 – Be specific

Copyblogger has a great rundown of what makes specificity so persuasive. In short, specificity means using concrete details wherever you can in your copy because those details help capture attention.

So, instead of writing “watch two dogs fight” write “watch a feisty Yorkie take on a Great Dane”. Details like this, especially in your subject line, help grab your reader’s attention and create an emotional response that drives clicks and opens.

Specificity also helps create a sense of believability and credibility, because a number like 83.4% feels too random (and thus, too real) to be made up. “Over 50%” is a much less intriguing number than “53%”, let alone “53.7%”. We find odd and unexpected numbers interesting, and the curiosity can push us to open just to see what’s going on.

Note: this is not an excuse to play fast and loose with your numbers. Stick to numbers that are real results you can back up; just be specific with the numbers you release.

#3 – Write in sentence case

The highest converting emails are always written conversationally, as though you were speaking to a friend instead of writing stilted business correspondence. That friendly tone starts with your subject line, as it’s the first part of the email your reader will see.

Write your subject line in sentence case to start with that friendly tone, much as you would if you were writing to a coworker or a friend.

Avoid Capitalizing Every Word or (worse yet) subject lines written IN ALL CAPS. They’re shouty, visually unappealing, and do very little to entice your readers to open your email.

#4 – Make them as long as they need to be

While you do want to be as concise as possible with your subject lines, you should not feel bound to an arbitrary word or character limit you heard from an email marketing expert five years ago.

Character limit rules for subject lines are well-intentioned, but are usually driven by character display limits in email inboxes rather than by customer behavior.

Being emotional and specific is far more important than fitting into a set number of characters, because those emotions and images are what will get your readers curious enough to open your email – even if it’s just to see the rest of your subject line.

And it’s understanding the behavior and preferences of your specific audience that will help you craft subject lines that get your emails opened. Some audiences like short subject lines. Others prefer longer ones.

How can you know which one your audience likes? Just follow this last principle:

#5 – Test your subject lines

To truly optimize your marketing – including your email marketing – you must test everything.

When it comes to emails, this means split testing your headlines to see which ones get more opens. This benefits you in two ways.

First, if you’re using autoresponders, you can set your emails to the higher-opened headline and leave the sequence to run, confident in your open rate.

Second, if you test consistently, your test results will start to reveal patterns in which subject lines your readers respond to. Knowing what types of subject lines and subject line content your audience opens the most can make writing these emotional, specific, and concise headlines much, much easier.

As with all copywriting, the key to great results is understanding your audience and what drives them. With subject lines, it’s a matter of knowing what content or subject will grab your reader’s attention, and then using these principles to create a subject line with the maximum chance of getting opened.

 

This article is Part 1 of ‘The Anatomy of a High-Converting Email‘, a series on using conversion copywriting techniques to write high-performing emails. Read the next installment in this series: How to write an email hook that keeps ‘em reading to the very end.

 

Katie Callaghan is a Sales Funnel Strategist and Conversion Copywriter helping growth-stage startups turn existing traffic into more customers, users, and revenue. You can find her at www.startupfunnelstrategist.com.

Related reading

Vector illustration with a magnifying glass focusing on a pie chart, a graph line trending upwards, and other metrics symbols.
Signpost with two signs pointing in different directions, one labelled B2B and one labelled B2C.