How to Write the Worst Email Subject Lines

email subject lines


Email subject lines, like blog titles and other headlines, are more crucial than what follows it. It doesn’t matter how great the special offer or lovingly crafted message on the other side of the click might be. You first need to overcome the barrier to getting that click.

With machine learning, natural language processing, and an organized, ranked, and scored ontology of marketing language, Persado has dissected the content, click-through, and conversion of millions of email subject lines.

What did we find?

A lot of common knowledge was confirmed, but a lot of so-called best practices turned out to be either terribly inconsistent or downright failures.

An example of the unexpected insight:

A recent study at Persado found that “awesome news” outperforms “great news,” but surprisingly (and counterintuitively), “good news” outperforms “great news.” Goes to show, you never know until you test, test, and test again.

SL Length

Also Known As It Doesn’t Matter How Long Your Subject Line Is As Long As It’s Good

The metrics used by companies like Litmus and Mailchimp are clumsy and myopic compared to our varied, forensically detailed algorithms that assess every letter of a marketing message.

For instance, our research has shown that Mailchimp’s suggestion to keep subject lines under 50 characters is not only unnecessary but could actually hinder click-through rates.

Since Mailchimp doesn’t provide insight into what message is conveyed and how it’s worded, the broad assessment of subject line length cannot logically conclude anything more than correlation, i.e. not causation.

For instance, operating under the directive of “keep it short” might lead copywriters to use shorter synonyms that just so happen to be more effective than their longer counterparts.

The advice also might lead the cautious copywriter to avoid fluffy language, wordplay, and puns that waste space, don’t add value to the messaging, and (as we’ve found in countless experiments) actually deter opens.

We find that a longer subject line (even 100+ characters) that uses the right emotional and descriptive language, in the right order, will always beat out a less well-executed but more prescriptively terse subject line.  


email subject lines

A universal practice that’s universally crappy: imperative statements and urgency.

Trying to alarm your audience to action is simply off-putting.

It’s a ubiquitous practice that’s become an age-old tale known as The Marketer Who Cried Wolf. Your audience is not only immune but averse to your fear-mongering.

It also belies quite the opposite of intimacy or consideration. As someone with way too many emails in my inbox, I don’t want to operate on your timeline. I want you to operate on mine, which is slow. Slow because I have so many dang emails.


email subject lines

“Click here to claim your discount” will never measure up to “We’re giving you a discount.”

The same goes for “Treat yourself” versus “You’re being treated.”

Be wary of any language that might imply that your audience needs to do something.

Offer value. Don’t dangle it in front of their faces.

Click Here…IF YOU DARE!!!

email subject lines

No, they won’t guess. Because they won’t care. Leave the suspense to Hitchcock, please.

Subject lines are a very different beast from creative marketing campaigns. Subject lines are utilitarian chunklets that lead your audience down a path, not a vehicle for fuzzy intrigue. 

We’ve found through countless campaigns that the right emotional connection paired with a specific indication of what lies ahead will consistently, and by a wide margin, beat out clever, cute, or vague subject lines.

The Final Equation: Time Minus Email Equals Less Time

email subject lines

If you can prove your specific value up front, no matter how many words it takes, you’ll get a higher ROI than making your audience guess.

It doesn’t take but a second longer to read 100 characters versus 50. But reading an email takes longer than deleting it. And deleting 10 emails probably takes slightly longer than unsubscribing from one.

Which all comes down to being considerate of the scarce resource that’s top of mind in any audience: Time. Reading an email is an investment. The subject line is your attempt to convince your audience of that investment’s value.

If you come across as bogarting your audience’s Time, either by urgency, beguilement, or directive, you’ll never get the response rate you hope for.

Email is a place for purpose. If you’re not explicitly clear about the purpose you serve in taking up precious, email-checking lifespan, to the rubbish bin you will go.

So, the secret? Make it clear that your message is worth their time and make sure that it actually is.

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