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Andrea Serventi
13 March 2018
Reading time: 8 min

How To Optimize Email Subject Lines And Open Rates

Let’s clarify the right subject line length once and for all and take a look at the details to pay attention to in order to increase campaigns’ open rates: from the preheader to power words, all the way up to an emotional approach.

Email marketing is a matter of details, even more so when discussing email subject lines: the hopes of an email being opened, or on the other hand of being forgotten or canceled, fully lie in the subject line.

In short, the subject line is a handful of words entrusted with the performance of one of the most important indicators: the open rate. In this case the details are those small and minimal measures which can shift balance, attracting openings or inhibiting them.

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Today we want to further explore this small but incredibly important line to understand where and how to optimize it, with the objective of increasing open rates.

The right subject line length? There is none

Let’s use data from GetResponse to answer this question: the analysis of about 2 billion emails demonstrated that the subject length most used by marketers is between 30-39 characters.

This data is overlapped by other, even more eloquent data: the subject lines that achieved higher opening rates had between 90-119 characters. A range of characters that blogs, ebooks, and in-depth articles unanimously consider too long, “unrestrained”.

What should we deduce from all this? The fact that a subject line is short enough to not be cut by email clients does not necessarily mean it will have positive opening trends. In short, the subject’s length does not seem to be the crucial element or factor closely linked to open rates. Breaking down this common perception is by itself already a precious certainty.

Be specific, exact, relevant

It is therefore a matter of details, rather than of universally valid rules. The parameters to take into consideration are more fleeting and linked more to analysis and testing, rather than to the number of characters.

Paradoxically, one of these fleeting parameters is specificity. Writing specific subject lines means bringing the “core of the matter” into the subject, the key concept that the email aims to communicate. Sometimes being specific requires including more text, and the first statistic given above relates to this: the emails opened most often are those with longer subject lines because they include more detailed information; inevitably, short subjects tend to be more generic and vague in introducing the message. On the other hand, how specific can you really be in 30 characters?

35% of recipients open emails based only on their subject line; it seems logical to think that the more specific the information conveyed in an inbox is, the greater the chances of involving, interesting, and intriguing the recipients. Even if this is not always the case. Sometimes being allusive and reticent is also rewarding. But we’ll take a better look at this aspect later.

Go long (but keep the key concept at the beginning)

If we now know that there are no particular limits for a subject line’s length, even the most loquacious subjects still have some constraints. Here’s an example from one of our recent launches.

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While not respecting the 30-character rule, we kept the heart of the message at the beginning of the subject line. In doing so the key concept is immediately readable, also from mobile devices.

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Smartphones cut out the least relevant part (Iconic Shelving by Tomado): a content surplus which the recipient can ignore without any detriment to us.

Write the preheader and make it complement the subject line

The preheader is often called the header, but it would be better to call it the summary; it is that short line of text in the recipient’s inbox that is displayed after the subject line. It is the part of the copy that integrates the subject and provides an additional frame of reference to help the recipient get an idea of ​​the email’s contents.

Far from being a service available to recipients, the preheader is a strategic element that works within the marketing funnel threshold as an element used to convince recipients to open an email, thereby decidedly helping to increase open rates.

Yet many companies still leave the preheader blank.

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This is not a wise choice if we consider another study: the average open rates of emails with a preheader is shown in orange, and the average open rates of emails without a header are shown in blue. That is not a slight difference, and it will be reflected in the final conversions.

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It explains and suggests without focusing exclusively on sales

Today marketing is greatly based on narration, on telling a story. The subject line is where the story should be outlined, anticipating the scenario that recipients will find inside the email. This means moving from a mere sales approach to a more narrative one.

The subject line is a type of business card: it’s best to avoid dulling it with a blatant invitation to purchase. The desire to sell is better left implicit.
The screenshot below shows a series of emails by Monoqi, an e-commerce design brand that stands out for its rather high sending frequency (an average of three emails per day).

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Rather than selling, Monoqi’s subject lines tell a story: each email brings attention to a design categorygenrestyle, or catalog of products for the home.

Highlight the advantage

A subject line’s ability to highlight the advantage conveyed by the communication is closely linked to the narrative dimension (you can find a case study further examining the topic here).

As we mentioned, nobody wants to find an explicit invitation to spend money in their inbox. It’s better to attract, entice, or persuade the recipient than to indicate an action to carry out (the call to action is a main element in emails, but it belongs to another level of text and certainly not the subject line). Use realism and pragmatism to find the advantage that best suits the product you are offering, the season, and the brand’s tone.

Avoid anything even remotely spammy

The keyword is transparency in this case as well. The recipient will be convinced by the offer, and certainly not by announcements and words which are shouted, such as the exhausted and overused formulas like FREE!, INCREDIBLE, or SUPER SALE.

Emails become spammy when they put an excessive emphasis on the supposed deal or benefits within the email: an excess of momentum that tends to characterize those emails which for all effects are spam.

Americans suggest putting aside the spammy emphasis with some best practices summarized in a deliberately equivocal acronym: S.P.A.M.

  • Short
    Brief and concise (after considering what was said here at the top regarding length).
  • Personable
    Address the recipient by name and raise the degree of personalization.
  • Attention-getting
    To capture people’s attention and stimulate curiosity.
  • Meaning
    The meaning or poignancy of the subject line that can anticipate offers and content.

Power words and the emotional approach

Each sector and category of sending has specific words that are more sensitive than others: these are the power words which recipients are particularly reactive and sensitive to. An (albeit partial) survey of power words was carried out by copywriter Karl Stepp, who calls them “power words for emotional selling.”

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Power words are just one aspect of the emotional approach. Besides words, you must consider tone and register. Four different approaches can be identified that brands must know how to respond to:

There are various possibilities for inducing the recipient to act by opening the email:

  • Specify or allude to a deadline
  • Leverage on FOMO (Fear of Missing Out)
  • Anticipate a negative scenario if the recipient fails to take advantage of the offer.

A bit of mystery never fails. Here’s how to instill suspense into the subject line:

  • Try the cliffhanger approach, which means leaving out details to arouse interest, without revealing anything. An example: Terme di Saturnia has increased bookings thanks to…
  • It starts with the outcome, offering readers a conclusion that gives them the chance to wonder how the story begins: How did Terme di Saturnia increase bookings?

Here’s how to infuse a bit of hype into the subject line:

  • Give your reader a sense of exclusivity, making him or her feel as if they are in a privileged channel with the brand.
  • Harness the power of data. For example: Did you know that 73% of customers see improvements after using this tactic?

There is a saying that goes more or less like this: “People won’t remember what you say, but they’ll remember how you made them feel”? Here are some gimmicks for applying this to email:

  • Work with emojis, which can highlight a state of mind better than many words if chosen carefully.
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  • Experiment with humor, perhaps playing with and using formulas usually associated with other fields. An example: Three marketers walk into a bar…

Call the recipient by name

Let’s imagine welcoming a totally unknown client or, conversely, recognizing the client, greeting them by name, knowing what their job is, and which field they work in. The dynamic field works exactly in this manner, personalizing emails.

Also known as dynamic tags, the dynamic field is the feature that lets you create special placeholder codes for customizing messages. These placeholders are automatically replaced with recipients’ data during a message’s delivery. They are elements inserted in square brackets (such as [name]) that the platform recognizes and replaces with the correct value for each single recipient.

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If someone calls us by name, we inevitably pay more attention. This is not only true in the real world, but also in the online world.

Find out what works better with A/B testing

An A/B test, also known as split testing, means submitting two or more different versions of the same message to a sample of recipients, analyzing the reaction to each version, and determining which one is most effective.

Testing is in the DNA of digital marketing. It only takes a few operations to compare different versions of a campaign: subject line, design, header, and copy. It is basically possible to test everything. Let’s look at some aspects of the subject line that can be tested to increase open rates.

Approach: affirmative or interrogative?

Ok, it’s a nuance, but it has important implications. All it takes is a simple inflection to create an increase or decrease in open rates.

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The company must have had good reasons to choose the interrogative variant. Who knows, perhaps the company chose to do so thanks to A/B testing.

Use of capital letters

If an all-caps subject line is not recommended (see the spammy section above), the use of capital letters in one word could give a strong impetus to open rates. Also in this case, A/B testing reveals which version will obtain better performance.

The use of emojis

Disturbing or pleasing? Emojis are small elements which are as frivolous as they are flashy. But precisely thanks to their ability to insert something vivid into an entirely text-based element, they can often push open rates to increase. A field to experiment with, trying out different emojis.

A/B testing is essential for anyone working in email marketing. This is why we suggest you MailUp: all you have to do is request a 30-day free trial, and you’ll have access to all of the MailUp platform’s A/B testing features.

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Andrea Serventi

I was born in 1986 in Milan, where I graduated in Modern Literature and started writing for online newspapers, magazines and TV news programs. Having now converted to marketing and the digital world, I am a Content Editor at MailUp: I read, listen, collect ideas, and write about what email marketing is and how to use it strategically.

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