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Discover Five Keys to Successful Email Subject Lines

Intouch Team

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David Ogilvy once remarked, When you have written your headline, you have spent eighty cents out of your dollar.” Advertising media has evolved considerably since the glory days of “The Man in the Hathaway Shirt,” but the value of a well-crafted headline has not diminished. Consumers in the era of digital communications are inundated by marketing messages in high volume and great frequency—particularly through e-mail. In order for an e-mail to survive the inbox avalanche, the subject line must first usher it through spam filtration, then entice the recipient to read more. Below are some tips for composing subject lines to serve both of these needs.

Keep the character count below 50

When it comes to subject lines, brevity reigns supreme. Shorter subject lines generally yield higher open and click rates than lengthier versions in comparative A/B testing. Long subject lines also run the risk of being truncated by a recipient’s e-mail program or provider—and this could result in the omission of keywords. A subject line should inquire, tease or call for action but not tell the whole tale. Curious about what constitutes 50 characters? Microsoft Word contains a handy function to provide the count. Take a look at the range of sample subject lines below:

Ten cool things you can do with Apple TV (41 characters)

Don’t miss out - huge airfare sales happening now (50 characters)

Important: account information for your 2010 taxes (50 characters)

Print your prescription records, questions to ask your doctor & heart health (76 characters)

Steer clear of words and phrases that trigger spam flags

Even the most reputable businesses with legitimate offers must adhere to this tenet. According to, more than 35% of spam is detected from the subject line of an e-mail. “Apply now,” “FREE___!” and “Information you requested” are just a few expressions to avoid. The word “free” isn’t necessarily the kiss of e-mail death—but its placement within the subject line is critical. The first word in a subject line sets the tone for spam scoring of the entire e-mail. When in doubt, refer to the wide array of resources available online, like this lineup of spammy no-nos or e-mail subject line test tool. You can even look to a thesaurus site to research more robust synonyms.

Remember the basics of good grammar and headline writing

The first e-mail subject line seen above would break any English teacher’s heart. As with a traditional sentence, subject lines should not be set in “Title Casing” or ALL CAPITAL LETTERS. Note the misspellings as well—very unprofessional and frankly unforgivable given access to electronic spellcheckers. As for the second e-mail subject line, if you think of subject lines in the same vein as newspaper headlines, then an ending period isn’t always necessary. Some of the most successful headlines impact without the use of punctuation. Unless the subject line is in the form of a question, skip the closing mark and other special characters. This is imperative when it comes to the exclamation point, which spam filters tend to feast upon.

Tell—Don’t sell—What’s inside

Like other vehicles of marketing, e-mails need to be carefully tailored to arouse the interest of the target audience—and it starts with an effective subject line. In 2007, JupiterResearch found that 35% of e-mail users open messages due to the contents of the subject. The lone objective of all e-mails is readership, which is aided by subject lines that Don’t shout aimlessly at recipients. Remember, cold sales copy produces cold subscribers. When constructing a subject line, ask “What is the purpose of this e-mail? Who are we talking to? What do we want the recipient to do?” Incorporate power words such as “discover,” “learn” and “now.” Instead of “FREE Webinar on foot health” how about “Register now to learn more about caring for hammer toes”? For additional information, check out these whitepapers on e-mail copywriting basics and 17 types of subject lines for different campaign scenarios.

Test, analyze, optimize

Interested in finding out how a series of proposed subject lines would perform against each other? Multivariate testing—more often referred to as A/B testing—offers feedback needed to proclaim a winner. The procedure: multiple subject lines are assigned to the same e-mail message and then sent to small but similar segments of an e-mail list. After a prescribed amount of time has elapsed, standard performance metrics—opens and clicks, in particular—are evaluated to determine which subject line generated the best returns. This approach is ideal in preliminary stages of campaign development but can also benefit triggered e-mails already in production. A/B testing doesn’t just apply to subject lines, either. Images, graphics, copy, design styles—so long as tracking is properly implemented within the e-mail, any content element can be tested. Pharma product managers—and especially their review committees—can be resistant to extra variations of emails because it creates additional work for them and it is difficult for them to see the value. However, a carefully planned approach to these variations can yield important findings and cost and time savings in the long run.

Although it might seem a mere fragment compared to the core of an e-mail, the subject line carries with it a tremendous amount of weight. It must avoid spam traps and peak reader interest for any further action to occur. The subject line should never be an afterthought of an e-mail campaign and can be smartly constructed by following a few key guidelines.


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