This is the worst mistake you can make in a business email, confirm experts

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Kayleigh Dray

Work emails are, as we all well know, a potential minefield; tone can be lost, meanings misinterpreted, and tensions can reach insane new highs with each person you passive aggressively CC in.

However, as it turns out, even the most banal office emails can cause trouble – and it’s all down to what you include in the subject line.

The experts at email management service Boomerang have analysed over a quarter of a million emails, and, in doing so, they have discovered that a well-crafted subject line is to key to a successful correspondence with colleagues.

When the subject is four words long, and no mistakes are made, you’re 41% more likely to receive a reply to your email.

But, if you start your subject sentence with a lowercase letter, then don’t expect anyone to message you back any time soon; it’s been dubbed the most off-putting thing you can possibly do in an e-message.

Other than writing something genuinely obnoxious, of course.

It's all in the subject line (and the day you send your email, too)

It's all in the subject line (and the day you send your email, too)

The people behind the study explain: “The most significant error [is] starting a subject sentence with a lowercase letter. Such emails only get a reply 28.4% of the time, compared to a 32.6% response rate for those with proper subject capitalization. 

“You could be one (shift) keystroke away from boosting your response rates by 15%.”

Want to improve your email skills even more? Don’t just check your grammar and craft a great subject line – also pay attention to which day of the week you’re sending it.

Or, more specifically, try to avoid sending any important correspondences on a Monday.

Not only are you more likely to make mistakes on the worst first day of the working week, but things are usually far more manic, and your mood is guaranteed to be lower (looks like the Bangles were onto something all these years).

“We looked at average subject line sentiment (a measure of positivity), and found that emails sent on Monday are the least positive,” explain the folk at Boomerang.

“Not only do emails sent on Mondays have the lowest subject sentiment on average, it’s a steep drop off from Sunday, which has the most positive email subjects.”

Hmm. While we don’t approve of people happily firing off work emails on the weekend (that’s your downtime, people), but it’s an important point to consider when crafting your messages.

To combat those ‘I don’t like Monday’ vibes, Boomtown suggest writing your Monday emails ahead of time and scheduling them to send later, so that you have time to review them before you go out.

You could also snooze emails you don’t want to deal with right now, or set up a recurring email to eliminate an email you’d otherwise have to type out each Monday.

It’s that or, you know, waiting until Tuesday. Good luck.

Images: iStock


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Kayleigh Dray

Kayleigh Dray is editor of, where she chases after rogue apostrophes and specialises in films, comic books, feminism and television. On a weekend, you can usually find her drinking copious amounts of tea and playing boardgames with her friends. 

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