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Keywords for killer subject lines

Which words to use — and avoid — from Adestra’s analysis

Is this the world’s best subject line: Alert: Free delivery, 50% off daily? And is this the world’s worst: Fw: Register for our Webinar and report? Probably not. But the words we use matter, and the words we use in subject lines matter a lot.

Keywords for killer subject lines
Snore subject Which words tanked in Adestra’s subject line analysis? Webinar, Learn and Report, among others.

Enter Adestra, a U.K.-based email service provider. It recently analyzed a random sample of more than 2 billion emails to learn which words work — and which don’t — in subject lines.

“Not all of your emails will get opened all the time,” writes Parry Malm, account director, Adestra. “Even market leaders routinely have less than half of their emails opened on a campaign-by-campaign basis.”

Here are some ways to improve your chances:

Focus on savings.

People like to save money, Adestra’s research found.

“In related news, water is wet,” Malm writes. (Turns out that’s not necessarily true: Have you heard about NEOs?)

So try phrases like Free delivery (+50.7%, +135.4%) or specify a percentage off (+10.5%, +27.4%).

Worried about using “Free”? It doesn’t affect delivery, though it doesn’t necessarily pull a good response, either, according to HubSpot’s research.

Opens: best to worst subject line words overall

KeywordOpen rate variance vs. averageClick rate variance vs. averageClick to open rate variance vs. averageUnsubscribe rate variance vs. average
Free delivery51%135%56%82%
Alert38%62%17%-63%
News35%48%10%26%
iPad32%20%-9%19%
Daily28%100%57%-75%
Weekly27%51%19%-50%
Sale23%61%31%32%
Voucher20%-2%-19%61%
Video19%65%39%-26%
New17%38%18%-3%
Bulletin16%13%-3%-23%
Gift12%-11%-21%21%
Exclusive12%0%-11%22%
Issue11%10%0%30%
Latest8%12%3%-10%
Offer7%-19%-24%22%
Subcription5%-19%-23%89%
Save3%-25%-28%18%
Win2%27%24%-3%
Download1%-6%-7%-28%
Newsletter1%-19%-19%3%
Free-3%-6%-3%-1%
Re:-4%-43%-40%91%
Only-4%-37%-35%12%
Get-9%-16%-8%3%
Don’t miss-9%-43%-37%33%
Register-10%-55%-50%28%
Fw:-14%-48%-63%135%
Today-16%-38%-26%5%
Webinar-17%-71%-65%9%
Report-24%-55%-41%-55%
Monthly-27%-37%-14%14%
Learn-36%-61%-39%-24%

Home free Free delivery outperformed all other words and phrases for opens and clicks-throughs, and second highest for clicks to open. But get a load of that unsubscribe rate!

You can’t fool all of the people all of the time.

“If you used the subject line ‘Free Beer!’ then guess what?” writes Parry Malm, account director, Adestra. “You’ll get a huge amount of opens. But unless the contents of the email actually pour your customers a beer, then you’ll have achieved nothing but short term response gain and long term brand harm.”

Same problem with Re: or Fw: at the beginning of your subject lines. They might get opened the first time, but you’ll get ignored the next time.

Bottom line: Don’t fake it, or you won’t make it.

Click rate: Best to worst subject line words overall

KeywordOpen rate variance vs. averageClick rate variance vs. averageClick to open rate variance vs. averageUnsubscribe rate variance vs. average
Free delivery51%135%56%82%
Daily28%100%57%-75%
Video19%65%39%-26%
Alert38%62%17%-63%
Sale23%61%31%32%
Weekly27%51%19%-50%
News35%48%10%26%
New17%38%18%-3%
Win2%27%24%-3%
iPad32%20%-9%19%
Bulletin16%13%-3%-23%
Latest8%12%3%-10%
Issue11%10%0%30%
Exclusive12%0%-11%22%
Voucher20%-2%-19%61%
Download1%-6%-7%-28%
Free-3%-6%-3%-1%
Gift12%-11%-21%21%
Get-9%-16%-8%3%
Offer7%-19%-24%22%
Newsletter1%-19%-19%3%
Subcription5.0%-19%-23%89%
Save3%-25%-28%18%
Monthly-27%-37%-14%14%
Only-4%-37%-35%12%
Today-16%-38%-26%5%
Re:-4%-43%-40%91%
Don’t miss-9%-43%-37%33%
Fw:-14%-48%-63%135%
Report-24%-55%-41%-55%
Register-10%-55%-50%28%
Learn-36%-61%-39%-24%
Webinar-17%-71%-65%9%

Deliver me from Webinars Free delivery scored best for click-throughs. Webinar is the word most likely to fail for click-throughs.

Marketing content marketing

Presenting a content marketing piece? Take Malm’s advice:

  • Rebrand your Newsletter (+0.7% opens and -18.7% clicks). Call it Alert (+38.1% opens and +61.8% clicks) or Bulletin (+15.8%, +12.7%). “The word ‘newsletter’ harks back to the day of receiving a posted and photocopied A4 list of stories,” Malm writes.
  • Don’t get caught in the clutter. Readers may be overloaded with content marketing messages. Book (-4.6%, -25.4%), Report (-23.7%, -54.8%,) and Learn (-35.5%, -60.8%,) are trending down. “When working on your content marketing plan, bear in mind that everyone else is too,” Malm writes. “Focus on differentiating your offerings.”
  • Deliver Daily (+27.8%, +100.3%) or Weekly (+27.1%, +50.6%). Monthly (-26.6%, -37.0%) may be too infrequent; after 30 days or so, you may lose top-of-mind position.

Bottom line, says Malm: “Content marketing works when the content isn’t crap.”

Unsubscribes: best to worst subject line words

KeywordOpen rate variance vs. averageClick rate variance vs. averageClick to open rate variance vs. averageUnsubscribe rate variance vs. average
Daily28%100%57%-75%
Alert38%62%17%-63%
Report-24%-55%-41%-55%
Weekly27%51%19%-50%
Download1%-6%-7%-28%
Video19%65%39%-26%
Learn-36%-61%-39%-24%
Bulletin16%13%-3%-23%
Latest8%12%3%-10%
Win2%27%24%-3%
New17%38%18%-3%
Free-3%-6%-3%-1%
Get-9%-16%-8%3%
Newsletter1%-19%-19%3%
Today-16%-38%-26%5%
Webinar-17%-71%-65%9%
Only-4%-37%-35%12%
Monthly-27%-37%-14%14%
Save3%-25%-28%18%
iPad32%20%-9%19%
Gift12%-11%-21%21%
Exclusive12%0%-11%22%
Offer7%-19%-24%22%
News35%48%10%26%
Register-10%-55%-50%28%
Issue11%10%0%30%
Sale23%61%31%32%
Don’t miss-9%-43%-37%33%
Voucher20%-2%-19%61%
Free delivery51%135%56%82%
Subcription5.0%-19%-23%89%
Re:-4%-43%-40%91%
Fw:-14%-48%-63%135%

Daily dose Daily is the most effective word in the study for maintaining subscription rates. Fw is most likely to send readers fleeing.

Adestra broke out its findings for B2B and B2C publishing and events, as well as retail and commerce and charities. Find killer keywords for your niche in the report.

___

Parry Malm, “2013 Adestra Subject Line Analysis Report: Keywords for killer subject lines,” Adestra, 2013

Parry Malm, “152 killer keywords for email subject lines (and 137 crappy ones),” eConsultancy, July 2, 2013

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