Why Short, Weird Email Subject Lines Often Beat Obvious Ones

Ok it’s Friday, so I’ll entertain answering this question today and prob give away far too much to my competitors.

“_“Hey Peter, why are your subject lines always so random?”_“ — - redacted

First off….

Fair question.

Sometimes they probably look like I’ve lost the plot.

But there is actually a method to my madness.

Our average open rate is 46.7%.

Short seems to help.

My 1 and 2 word subject lines averaged 48.0%.

The 3+ word ones averaged 45.7%.

And the top ones are not the polished, corporatey, “clear value proposition” ones either.

The best performers tended to fall into a 3 buckets.

1. Short:

• Lucky? (55.01%)

• Hindsight (53.48%)

• ugly (51.81%)

• Crocs (51.73%)

2. Useful (with a promise of value):

• 16 Ways to Improve Your Brand (53.07%)

• eCommerce AI Wiki (52.58%)

• Cheatsheet (49.56%)

3. Vivid:

• high five (53.92%)

• Where can I find the condensed milk? (51.29%)

• Agony Aunt (47.56%)

• inflatable dartboard (47.13%)

And yes, I have also had some absolute duds.

• The ol’ switcharoo... in reverse (38.48%)

• Set limits (39.15%)

• 0.4s (41.54%)

• Magic Money Machine (42.09%)

And some of my more obvious subject lines did not exactly set the world on fire either.

• CRO Agent Update (42.08%)

• How to Increase CR & AOV in 2026 (42.78%)

• Is CRO something you need? (43.20%)

• Before you spend another 10k on ads... (43.82%)

Useful? Sure.

Compelling in an inbox? Not really.

Here is my working theory.

The subject line is not there to explain the email.

It is there to win the open.

From a CRO point of view, it is a headline competing for one click.

From a psychology point of view, my best subject lines tend to do three things:

• They are easy to process

• They break the pattern

• They create a small information gap

This is a mix of processing fluency, incongruity, and curiosity.

In other words…

Your brain recognises the words quickly.

But the meaning or relevance does not land straight away.

That split second of “I get these words” followed by “wait, what the hell is he talking about?” is what makes your brain want to open the email.

That is also why I prefer closed loops over open loops.

An open loop is something deliberately unfinished.

“You need to see this”

“This changed everything”

“Do not make this mistake”

It works by withholding the point and making you click to close the gap.

It can work.

But it can also feel like tired clickbait when everyone uses the same trick.

A closed loop is different.

It is a complete thought.

It stands on its own.

But it still feels unresolved in context.

• “Crocs”

• “ugly”

• “Lucky?”

• “Hindsight”

• “high five”

• “Where can I find the condensed milk?”

Those are closed.

The phrase itself is complete.

What is missing is the relevance.

Because if you make it too clear it feels like marketing.

Too weird and it feels like nonsense.

And too long it gets skimmed past.

So when I write subject lines, I am usually asking:

• Can this be shorter?

• Can I swap the obvious line for something cleaner?

• Can I make it feel slightly off without making it confusing?

• Can someone read it in under a second and still want to know more?

So yes, the subject lines could appear random.

But not by accident.

Chat soon,

Peter