Have you ever wondered why some cold emails get replies while others fall flat?

A recent study revealed a surprising truth: misleading your recipients, even unintentionally, can sink your response rates.

Researchers tested two simple subject lines on 1,000 top executives, C-level and VP-level leaders from Fortune 500 and Inc 500 companies. Both subjects were paired with the same body copy and both had a similar open rate of about 50%. 

But the response rates? 

Night and day.

What happened… and how can you avoid making the same mistake?

Let’s dive in.

The Experiment: Quick Question vs. False Promises

Two versions of the email subject line were tested:

  1. “Quick Question”
  2. “15 Second Question for Research on Annoying Emails”

Both had a clear intent: ask for feedback. The body copy was identical, so the only difference was the subject line.

The results were surprising:

  • Both emails had a similar open rate (~50%).
  • But the reply rates were dramatically different:
    • “Quick Question” earned 66.7% of the total replies.
    • “15 Second Question” earned just 33.3% of replies.

That’s a difference of over two times the response rate simply because one subject line over-promised on time commitment.

The Lesson: Avoid False Promises in Cold Emails

Let’s be honest: executives are busy people. 

They’ve seen every cold email trick in the book, and they don’t appreciate being misled, even subtly.

At first glance, the subject line “15 Second Question” seems harmless. 

After all, it’s catchy and conveys brevity, right? Wrong.

The problem lies in the promise. 

When recipients opened the email, they likely realized the request wasn’t quite as quick as advertised. 

That small mismatch, even if unintentional, created friction. And in cold emailing, friction kills response rates.

Here’s why this matters:

  • Trust matters. Over-promising, even slightly, erodes credibility.
  • Executives value their time. If you claim your email will take 15 seconds, it better deliver.
  • First impressions stick. Misleading subject lines signal that the sender might waste their time.

The takeaway is clear: respect your recipients’ time and avoid false promises. 

Small missteps can cost you big results.

How to Write Cold Emails That Actually Work

Want to craft cold emails that resonate and get replies? 

Here’s what you need to focus on:

1. Honesty Above All Else

Your subject line sets the tone for your email. 

Make sure it’s:

  • Accurate
  • Honest
  • Aligned with the body content

For instance:

  • “Quick Question” works because it’s short, simple, and true.
  • “Thoughts on [Specific Topic]?” sparks curiosity without over-promising.
  • “2-Minute Favor?” clearly respects their time.

2. Simplicity Wins

Overthinking subject lines can backfire. The best ones are short and straightforward. 

Busy professionals don’t have time for fluff.

Avoid gimmicks like:

  • Clickbait phrases (“You won’t believe this…”).
  • Overly specific promises (“This will take exactly 12 seconds!”).

Instead, stick to what works: clarity and curiosity.

3. Test, Test, Test

The only way to know what subject lines resonate with your audience is to test them. 

Run A/B tests like the one in this experiment. Monitor open rates and response rates to see what works best.

Remember: 

Small tweaks, like switching out a single phrase, can double your cold email response rate.

What Makes a Good Subject Line for Cold Emails?

Let’s break it down:

  • Short and Direct: 5-7 words is the sweet spot.
  • Curiosity-Driven: Make them want to open the email.
  • Honest and Transparent: Never over-promise or mislead.

Here are a few examples of good subject lines for cold emails:

  • “Quick Question”
  • “Can I pick your brain?”
  • “Thoughts on [specific topic]?”
  • “2-Minute Favor?”
  • “Quick follow-up on [X]”

Each of these is clear, respectful, and effective. 

More importantly, they avoid triggering skepticism.

The Results: Small Changes, Big Impact on Cold Email Response Rate

This experiment proves a powerful point: The smallest details like your subject line can make or break your email’s success.

By avoiding false promises, the “Quick Question” subject line earned over twice the response rate compared to the misleading “15 Second” version.

That’s a game-changing difference. And the lesson is clear:

  • Be honest.
  • Be direct.
  • Respect your recipient’s time.

Cold emails that actually work are simple, clear, and trustworthy. 

When in doubt, under-promise and over-deliver.

Craft Smarter Cold Emails

If you want to boost your cold email response rate, stop trying to trick or impress your recipients. Executives and most busy professionals value honesty over cleverness.

Next time you write a subject line, ask yourself:

  • Is it accurate?
  • Is it clear?
  • Does it respect my reader’s time?

Small tweaks can lead to big results. 

Just like the “Quick Question” subject line proved, sometimes the simplest approach wins.

Now it’s your turn: How will you refine your next cold email to get more replies?

You can take on this challenge yourself or, if you want to ensure your campaign goes smoothly, you can get the help of an email marketing agency.