The Best Words for Email Subject Lines

A single word can be the difference between success and failure of email marketing campaigns. One word can substantially increase or decrease click-through rates. That’s why marketers look to industry research that identifies the best-performing subject lines.

In one such effort, Adestra analyzed data from more than 3 billion emails that were part of 125,000 global campaigns by organizations in four industries — retail/B2C, conferences/events, media/publishing and B2B. The research involved more than 400 million opens and more than 55 million clicks.

Researchers selected the 300 most popular words, characters and two-word phrases and compared their performance against the average.

Here’s our summary of their results.

Timeliness often works well. Words like “breaking” and “bulletin” boast higher than average open rates. Emails with “Thank you” in the subject line have the highest open rates. However, they are emailed receipts of purchases that consumers naturally open.

Subject lines that separate topics with pipes, such as “Sale now on | New lines added | Win trip to Dubai | Share your pics with #summer2015rules”) also perform significantly better than average. Academic, mundane words like “journal” and “forecast” are the worst performers.

Email Marketing Depends on the Industry

The success of subject lines varies depending on the industry, Adestra emphasizes. Here’s an overview of the main points.

In the retail sector, contrary to general intuition, larger discounts tend to produce the worst open rates. The subject line with “10% off” produced the best open rate; “50% off” had the worst rate. People suspect a large discount is too good to be true. On the other hand, larger offers once opened have better click through rates, presumably because consumers are already interested in the offer.

Marketers promoting events and conferences face the challenge of attempting to differentiate their events. Many employ general words, such as “agenda” or “speakers,” that focus on the event rather than benefits for their audience. Messages with the word “advice” performed better than average.

In the media publishing industry, strong editorial content prompts higher open and click through rates. Editors, who think differently than marketers, control email subject lines. Although email campaigns should still focus on editorial content, they can improve if editorial and marketing departments work together, researchers say.

In the B2B and financial services sector, reducing unsubscribes is paramount. The industry features high-value products, a long sales cycle and a convoluted sales process. If content is marginal and not targeted correctly, the audience may become disengaged, leading to unsubscribes.

CyberAlert’s Complete Guide to Headline Writing for Blogs, Conversion Pages and Email offers additional insights about better-performing words. Another worthwhile reference is Email Subject Lines & Tips from Dozens of PR & Marketing Articles.

Marketers should use A/B testing of subject lines to determine which version performs best. Lessons learned from each A/B test of email subject line should be applied to subsequent marketing emails. Editors of corporate newsletters can also use A/B testing to determine subject line formats and subjects that achieve the best open rates.

Other factors contribute to open rates other than the subject line.

The “From” name. Marketers can use the brand, a person’s name or other options.

The day of the week and time of the day. Tuesday at 4 p.m. is statistically the best time for email marketing. However, the results are fleeting. If marketers target that time, it will soon be the worst time for email campaigns. Uncontrollable external variables, like the weather, also have an impact.

The email list. Cleaner lists produce better results, but marketers have limited control over their lists.

Clean Email Lists

Marketers recommend growing email lists organically to produce clean email lists and higher-quality leads. Internet marketing expert Neil Patel in offers these solutions:

Launch a sidebar opt-in box. Ask your web designer to create a special opt-in sidebar on your webpage. If you use a WordPress blog you can copy and paste the opt-in’s code using WordPress Widgets.

Offer something for free. Offer free products or white papers. In exchange for the download, ask the visitor for an email address. Check that it is valid with email verification, also known as double opt-in.

Launch an end-of-post opt-in box. This resembles the sidebar opt-in, except it pops up when a visitor reaches the end of a webpage.

Create a special landing page. An entire landing page enables marketers to explain the full benefits of singing up for the email program.

Track your open rates. If someone doesn’t open your email two times in a row, send them a unique email the third time — one that is more personalized and less promotional.

Bottom Line: To obtain better open rates, marketers should use certain words that research shows work better in subject lines and avoid words that perform worse. The keywords vary by industry and audience. Performing A/B tests of subject line can help identify the better performing subject line words. A clean email list is just as important as subject line in achieving higher email open rates.