Email Marketing Explained: The Definitive Word on Subject Lines

Everyone hopes their emails get read. We know that along with having a good relationship with the recipient, writing exceptional subject lines increases the chances our message gets opened in a crowded inbox. And everyone who writes email for sales and marketing purposes has read or heard something about writing the best subject lines … you know, the ones that are automatically opened because they’re so good.

Stop right there. You can quit your quest for the holy grail of subject lines because it doesn’t exist. I’m telling you today the secret sauce is there is no secret sauce. No ‘opens’ are automatic. However, you don’t need to despair. Evidence indicates there are reliable ways to attract readers. How do you reliably attract readers? First, by making them care about you, the sender. Do they know who you are, and did they opt in to receiving messages from you? Is it even clear the message is from you?

email subject line

After conveying identity, you reliably attract readers by keeping the subject line brief and informative. By brief, we’re talking no more than 40 characters, via Nielsen Norman Group research linked above. Another study by Retention Science found that subject lines with 6-10 words had the highest open rates. These two findings together are consistent if the 10-word subject lines consist of short words.

The key is that in a few words, you give readers enough specific information to decide whether they want to open your message or not. Keep it too vague, and you’re increasing what smart user experience professionals call the interaction cost of opening your email to determine its content (meaning the reader has wasted time if the email turns out to be undesired, and the unclear subject line forced the reader to open the message to figure it out).

So, what to make of all the (occasionally contradictory) information you find in the wild about Unstoppable Email Subject Lines and other nonsense? Be skeptical of the hyped-up headlines and evaluate data on a case-by-case basis. Certain audiences may, in fact, be more likely to react favorably to discouraged email subject lines than others—for example, breaking the 40-character limit in order to present relevant story choices in a concise manner makes sense if you’re sending a newsletter with multiple items.

The audience that is accustomed (and open) to reading your newsletter would likely receive it well and might just hover over the subject line to elicit the preview tag of the entire subject. (I myself am one such reader; that’s one of my favorite tricks!) Those readers would choose to open or ignore your message based on the subject line’s indication of its various topical contents (regardless of characters), and would be grateful that you presented the relevant story choices in a concise manner. But as a rule, brevity and descriptiveness win out across the board.

So much of what determines an email ‘open’ comes down to knowing what makes somebody tick. My favorite stat from the Retention Science study referenced above is:

  • Emails with subject lines referencing movies or songs: 26% open rate
  • Emails with more traditional subject lines: 16% open rate

What does this tell us? People like movies and songs. Hey, a news flash! What does it not tell us? What were the actual contents of the message, and did the message itself match up to the expectations the reader had from the subject line? It’s not hard to imagine using a clever pop-culture reference in a subject line to get somebody to open an email. It’s also not hard to envision that person getting annoyed because the message itself was not valuable to them. In this case, you not only increase the reader’s interaction cost, but risk turning them off further due to a perceived “bait and switch.”

Again, it comes down to knowing what makes a reader want to open your email (repeatedly, over time) in the teeming inbox jungle. If you just want a message to get opened with no concern for losing a reader, then make Star Wars and Katy Perry subject line references all day. Don’t expect everyone to take you seriously, though, unless you’re sending to those fan clubs.

Paul Richlovsky

About Paul Richlovsky

Paul brings a writing and teaching background to his decade-long marketing career. He advises clients on content strategy and editorial direction. He is an enthusiastic marketing automation practitioner and active member of the Cleveland Marketo User Group. He has written/edited multiple marketing guides, including those aimed at healthcare, higher education, financial services, B2C brands and manufacturing audiences. With a BA in English from the College of Wooster, he is also the author of a collection of poetry, "Under the Lunar Neon."He is particularly interested in usability, digital governance, ballroom dancing, bachata, racquet sports, and romping with his niece and nephews.

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