The Subject Line Hurdle For eMail Success

According to a study by Yes Lifestyle Marketing, the email subject line has long been a defining component of email performance; it’s the immediate determinant of whether a message will be opened, ignored, moved to the junk folder or instantly deleted. This makes the subject line a major factor of how a campaign performs and how it contributes to a brand’s bottom line because a message that isn’t opened cannot result in any clicks, conversions or revenue.

There are a variety of factors that impact the effectiveness of a subject line – the content it promotes, the offer it extends, the timing of the email send, the sender’s industry, the type of message the subject line is introducing, the presence of personalization and more. However, something as seemingly innocuous as the length of the subject line – especially in combination with other subject line components like industry, message type or offer – can make or break a campaign’s open rate, says the report.



This report, based on an analysis of more than 7 billion emails sent in Q2 2017 through Yes Lifecycle Marketing’s cross-channel platform Yesmail360, dives into how various subject line components can impact email performance.

Key findings include: 

Personalized subject lines (like those including a recipient’s name or purchased/browsed items) generated 50% higher open rates, 58% higher click-to-open rates (CTO) and almost 2.5 times the unique click rates of subject lines without personalization. 

  • Overall, subject lines between 1 and 20 characters generated a 31% higher open rate than the average for all emails sent in Q2 of 2017. 
  • Subject line length impacted open rates most significantly for the retail and technology industries. 
  • For triggered messages such as abandoned cart, birthday and reviews/surveys, including a specific offer in the subject line, drove better open rates and higher conversion rates.

Personalization has long been the subject of many theories, tests, and marketing strategies, says the report. Subject line personalization, in particular, has gained a lot of traction in recent years with many brands using different attributes to personalize their communications, most frequently the subscriber’s name. Considering the proportion of Q2 subject lines that were personalized via a data merge and the type of performance they drove, only 2% of ALL emails sent in Q2 2017 had personalization in their subject lines.

However, they significantly outperformed emails without subject line personalization across all engagement metrics; they generated 50% higher open rates, 58% higher CTO rates and more than double the unique click rates of messages without subject line personalization.

One thing for marketers to consider when looking at the impressive performance of subject line personalization is that there is a higher likelihood for these messages to either be triggered campaigns or be sent to a smaller and potentially more engaged audience. Marketers tend to have more and better-quality information about consumers who have previously engaged with their brand either through completing a purchase, submitting preference center information or being a member of a brand’s loyalty program.

Subject Line Personalization

Type of Subject Line Personalization

Proportion of All Emails

Open Rate

Click Rate

CTO Rate
















Source: YES! LifecycleMarketing, August 2017

Subscriber name accounts for about half of all subject line personalization, says the report. The other half is made up of various data attributes that enable marketers to get creative. The study discovered that many savvy brands that drove high email engagement incorporated items from consumers’ abandoned carts, or inserted loyalty program attributes like expiration dates, status achieved, or number of points remaining until the next membership milestone.

The ‘other’ category of subject line personalization generated slightly higher open rates than name personalization but drove significantly higher unique click and CTO rates. The ‘other’ category suggests a higher degree of relevance, since it could contain unique details about loyalty status, product categories, and more to enhance the customer experience.

If marketers want their subject lines to fit neatly within the confines of the mobile screen, it is best to keep them under 35 characters, says the report. On mobile devices, subject lines get cut off earlier than they do on bigger screens, but the pre-header text is always visible in the inbox right underneath the subject line, giving marketers the opportunity to lengthen or otherwise enhance the email subject.

Almost three-quarters of all email subject lines from Q2 2017 were between 21 to 60 characters long, including spaces and punctuation. Considering the maximum number of characters that are visible on most mobile devices is around 35, this means more than half of these subject lines were cut off and replaced by ellipses when viewed on mobile.


On average, this ‘middle’ group underperformed compared to both subject lines under 20 characters and subject lines over 60 characters. The shortest subject lines drove the best open rate, a 34% increase over the ones between 21-60 characters.

Perhaps because the vast majority of subject lines fall between 21 and 60 characters (74%), there is a lot of competition for opens within this group. It should come as no surprise then that subject lines between 21 and 60 characters generate a lower open rate (13.8%) compared to both shorter and longer subject lines. Furthermore, because almost half (45%) of all Q2 subject lines are between 31-50 characters, this group was even less effective with an open rate of 13.5% due to the even bigger competition, says the report.

Overall, subject lines under 20 characters perform best, generating an open rate of 18.5%. Within this high performing category, even shorter subject lines, the ones under 10 characters, tend to drive the best open rates with an impressive average of 26%.

There are three things to note about this trend: 

  • Less than 1% of all subject lines fall in the less-than-10-characters category. 
  • 45% of subject lines in that category belong to triggers, driving home the point that a high degree of relevance is essential for generating strong engagement. 
  • Less than 5% of all subject lines are shorter than 20 characters, which helps this category stand out among the longer ones in the inbox

84% of retail subject lines fell between 21 and 60 characters with 53% falling between 31 and 50. This mid-length category generated the lowest open rate for the industry at 12.8%.

Contrastingly, the highest open rate for the retail sector (18.3%) was generated by subject lines boasting fewer than 20 characters, which only accounted for 5% of all retail emails. One possible reason for the comparative success of shorter retail subject lines is that many of them were triggered campaigns, particularly abandoned cart, account update and welcome.

In the retail industry subject line performance peaks on two opposite ends of the length spectrum. While subject lines longer than 60 characters do not perform as well as those under 20, they still drive a 15.3% open rate, a 20% increase over the open rate generated by the most frequently used subject line length for retail.

Email subject line is a key component of campaign success because it is the single most important determinant of opens, concludes the report. Within subject line, there is a variety of factors that can affect campaign performance such as length, personalization, a brand’s industry, the type of message the subject line pertains to, and more. This report looked at how a number of those factors worked in combination and how they contributed to campaign performance across different industries and message types.

For additional information about eMails from Yes Lifecycle Marketing, please visit here.

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