Building Your Best Subject Line

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Personalization, character count, and message type are all variables marketers need to keep in mind

Creating the perfect subject line is an art form, but there's also a lot of science and data that goes into the craft. For its new subject line benchmark report, Yes Lifecycle Marketing analyzed more than seven billion emails sent in Q2 2017 via its cross-channel platform Yesmail360. 

Here are some of the key findings featured in the report.

Personalization performs

Email personalization is hardly a novel concept, but how many marketers are actually tailoring their subject lines for the intended recipient? The answer: Not many.

According to the report, just 2.3% of emails analyzed contained personalized subject lines. Of this group, 1.1% were personalized by name. The other 1.2% were personalized based on other factors, like products in abandoned carts or loyalty program status updates (e.g. expiration dates, tiers, or point counts).

Emails containing the latter form of personalization performed better than those containing name-based personalization. Consider: The report found that emails with name-based subject lines experienced a 21.2% average open rate, a 2.9% average click rate, a 13.8% average click-to-open rate; however, emails containing subject lines based on other personalized attributes experienced a 22% average open rate, a 3.8% average click rate, and a 17.5% average click-to-open rate.

"First name [personalization] initially got a bad rap," says Marie Honme, senior marketing strategist for Yes Lifecycle Marketing. "It started feeling generic and not effective, but it turns out that even just putting a name does enhance the relevancy for that person."

Both types of personalized emails still performed better than emails containing generic subject lines. These non-personalized messages produced an average open rate of 14.1%, an average click rate of 1.2%, and an average click-to-open rate of 8.7%.

Honme attributes the lack of personalized subject lines to data integrity issues and marketers not thinking beyond name-based personalization. 

Characters count

When it comes to subject line length, 21 to 60 characters appears to be marketers' sweet spot. According to the report, about three-quarters (74%) of emails analyzed contained subject lines that fell within this range. Twenty-one percent contained subject lines with 61 or more characters and 5% featured subject lines with one to 20 characters.

Thirty-five is generally the maximum number of characters a marketer can feature in a subject line without it getting cutoff on a mobile device, notes the report. This includes spaces and punctuation. Therefore, the aforementioned data would suggest that a significant portion of analyzed subject lines weren't getting fully read.

But how does subject line length actually impact performance? Based on the report's findings, it looks like shorter is better.

According to the study, emails containing subject lines with one to 20 characters experienced an average open rate of 18.5% — higher than the average open rates for emails containing subject lines with 21 to 60 characters (13.8%) or 61 or more (14.8%). 

Emails with subject lines between one to 20 characters also performed better when it came to average unique click rates (2.4% versus 1.2% and 1.3%, respectively) and average click-to-open rates (12.9% versus 8.5% and 8.9%, respectively).

However, Honme says character count isn't the only thing marketers should consider when crafting subject lines.

"Just limiting the number of words will probably not do it for you," she says.

Message type matters

Message type can also be a factor. 

For instance, the study found that 45% of emails containing fewer than 10 characters in their subject lines were triggered emails. Granted, not all marketers kept their triggered message subject lines brief.

According to the study, welcome emails containing subject lines with one to 20 characters outperformed those containing 21 to 50 characters or 51 to 90 characters when it came to open rate, unique click rate, and click-to-open rate. However, only 7% of welcome emails contained subject lines that fell into the one-to-20 character range. Sixty-nine percent of these messages contained subject lines with 21 to 50 characters and 23% featured subject lines with 51 to 90 characters.

Similar patterns appeared among abandoned cart triggers. Although emails containing 11 to 30 characters performed the best in terms of engagement, the majority of these triggered emails (62%) contained subject lines with 31 to 50 characters.

The opposite occurred, however, among browse abandon emails. Emails containing 31 to 60 characters performed better than those containing 11 to 30 characters when it came to average open rates (40.6% versus 35.5%), average unique click rates (6.6% versus 4.9%), and average click-to-open rates (16.2% versus 13.9%). Still, 61% of browse abandon trigger emails contained 11 to 30 characters.

Homne encourages marketers to test their subject lines for triggered emails regularly and to avoid adopting a "set it and forget it" mentality.

"If it's a trigger, I would just try to refresh it as often as you could or test things," she says.

The impact of subject line length can also vary by industry category. For instance, while emails from consumer services companies experienced their highest average open rates (15.6%) when their subject lines contained 21 to 60 characters, emails from retail and wholesale companies performed better when their subject lines were between one to 20 characters (generating an average open rate of 18.3%).

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