The ONE thing you should ALWAYS keep out of an email subject line

xero email

Getting your email noticed in the sea of an elusive client or potential investor’s busy inbox can be a daunting task, but a recent study has shown there’s ONE THING you should NEVER do when crafting the perfect subject line.

Email productivity tool Boomerang analysed over 300,000 publically available email threads to discover what does and doesn’t work when it comes to subject lines. In a blog post, the company revealed subject lines written with a liberal use of caps lock get markedly fewer replies than those written without.

Read more: Amazon’s chief technology officer received a pitch for his own product over email

Out of the 301,816 email subject lines analysed, the company found only 1687 were written entirely in capital letters. However, of those 1687, only 34.6% received a response, compared to the 50% response rate for subject lines written without all words capitalised.

“On average, users who wrote an email with an all uppercase subject received a reply 30% less often, relative to the other emails in the set,” the company said.

Subject lines written in all caps are also far more likely to be picked up by an inbox’s spam filter, with a number of popular spam filters using all-caps subject lines as a sign of an unsafe or superfluous email.

“It’s a bit ironic, but a critical email with a subject of “URGENT: PLEASE READ” could be less likely to make it to someone’s inbox compared to an email with a less dire subject line,” Boomerang said.

And if you’re wondering who are the most likely offenders when it comes to VERY LOUD subject lines, topping the list are users of American mail service AOL, followed by Hotmail and Yahoo users. Gmail users were the least likely to keep the shift key held down, with just 0.1% of all-caps subject lines coming from Google’s mail service.

Boomerang has also looked into the best way to sign off an email. In research published earlier this year found ending an email with the pre-emptive “thanks in advance” receives a 65.7% response rate. Ending an email with a simple “thanks” or “thank you” received response rates of 63% and 57% respectively, and easygoing “cheers” generated a response 54.4% of the time.

Never miss a story: sign up to SmartCompany’s free daily newsletter and find our best stories on TwitterFacebookLinkedIn and Instagram.


Notify of
Inline Feedbacks
View all comments
SmartCompany Plus

Sign in

To connect a sign in method the email must match the one on your SmartCompany Plus account.
Or use your email
Forgot your password?

Want some assistance?

Contact us on: or call the hotline: +61 (03) 8623 9900.