A recent report from cross-channel marketing platform Yes Lifecycle Marketing suggests that 21 might be a magical number in email marketing.
The vast majority of email subject lines vary between 21 and 60 characters, according to Yes Lifecycle Marketing, but an analysis of more than 7 billion emails sent in the second quarter of 2017 suggests that shorter subject lines generate higher-than-average email engagement rates.
Subject lines set the tone for the remainder of the marketing message, and are a pivotal component to increasing subscriber engagement. No email marketer can succeed unless their messages are first opened, and a subject line can make or break the sale.
Email subject lines over 21 characters account for three-fourths of all email messages, according to the study, although they only generate an average email open rate of 13.8%. This statistic is magnified in the retail industry, where 84% of emails have more than 21 characters in their subject line, generating an average open rate of 12.8%.
In contrast, emails with subject lines under 21 characters have double the unique click rates and a 31% boost in average open rates. Subject lines with 10 characters or fewer averaged an email open rate of 26% -- nearly double the 14.2% average open rate across an aggregate of emails.
Shorter subject lines are also a rarity in email marketing. Subject lines of 21 or fewer characters account for less than 5% of all email subject lines, according to Yes Lifecycle Marketing -- although they generate higher engagement. Subject lines with 60 or more characters are four times more likely to be used by email marketers, even though most mobile email clients will off subject lines of 35 characters or more.
It would be mistake to treat email like a siloed marketing channel, particularly when the majority of emails are now read on mobile devices. Six-out-of-ten retail email messages were opened on a smartphone in the first quarter of 2017 according to Movable Ink’s latest Consumer Device Preference Report. Desktop computers only accounted for a quarter of email opens that quarter, while 14% of emails are opened on tablets.
"Over half of email opens happen on a mobile device -- and the number is still growing,” says Michael Parapetti, art director of creative and agency services at Yes Lifecycle Marketing. “To deliver the best user experience for a mobile audience and their customers, marketers should optimize messages using responsive design techniques based on screen size, platform and orientation. This is a simple step to ensure a great mobile user experience for these customers."
It would also be worthwhile for brands to identify which email clients are most popular among their subscribers, and then to ensure that email messages are optimized for those clients via A/B testing. The top three most popular email clients in the United States last year -- Apple iPhone, Gmail, and Apple iPad -- accounted for 66% of email opens in 2016, according to Litmus.
Subject lines have the highest impact on engagement rates in the retail and technology industries, according to Yes Lifecycle Marketing -- but were not shown to be a significant factor in email engagement for financial services, publishing, and travel industries.
Only 2% of email subject lines included some level of personalization, such as a subscriber’s name, although these emails generate a 50% higher open rate than emails without personalization.