I open Gmail.
Here’s what I see:
As someone who has written hundreds of holiday campaigns, I judge each subject line like a sommelier judges their chardonnay from Burgundy.
“IT’S BLACK. FRIDAY.”
You don’t say?
“Shocking PRICE DROP!”
A discount during Black Friday… consider me astonished.
“24 Hours Left to Shop Our Black Friday”
In other words… buy now, ya prick.
I’m not even joking, each year November and December roll around, marketers seem to run out of creative juices.
And honestly, I can’t blame them. When you’re pushing the same offer for an entire month, you eventually run out of angles.
That’s why today I’m sharing a simple, practical copywriting formula that makes writing subject lines a whole lot easier.
I use this formula when I have to write a ton of email campaigns and I don’t have the mental bandwidth to come up with crazy good subject lines.
It still consistently gets me and my clients 50%+ open rates.
Before I share it with you, here’s a disclaimer:
This subject line framework is merely a tool — it’s supposed to make your life easier – but remember, every formula has its holes.
It also doesn’t magically increase your list quality, nor the quality of your email content. Those things also have an impact on your open rates.
The formula I’m talking about is:
The 4U’s copywriting formula by Robert Bly
If you’ve read my Emails that Sell series, you’ve probably heard me mention the 4U’s a couple of times.
It’s actually a framework made for writing compelling ad headlines, but it works perfectly well with subject lines too.
Here’s what the 4U’s stand for:
1. Urgent
Does your subject line give a reason to act now? Is it time-sensitive?
Most BFCM campaigns, like “Last Chance To Save 40%,” tick the box here.
2. Unique
Does your SL say something new or in a fresh way?
More importantly, does the SL read like it could come from any other brand?
For example, there’s nothing unique about “Holiday Deals You’ll Love,” but “The Candle That Smells Like a Fresh Bakery (20% OFF)” is a whole different story.
3. Ultra-specific
Does the SL make the reader want to read further? Or is it vague?
A SL “3 Gift Ideas for Your Tech-Obsessed Uncle” is much more targeted than “Our Holiday Gift Guide.”
4. Useful
Does it promise a benefit like this SL right here?
“Fluffy Socks That Actually Stay on Your Feet… 50% Off”
Usefulness is where most holiday campaign subject lines fall short.
Now, let’s have a look at the 4U’s in practice…
Use this AI prompt to generate 10 ready-to-use subject lines
Let’s take a random holiday campaign and copy+paste it into Claude.
Here’s one by Alpha Dog:
The subject line of this email?
“Holiday Gift Guide: Dog Supplements Edition”
No urgency, no benefits.
We can do a lot better.
I copy+pasted this prompt, and here’s what Claude gave me…
Are these subject lines perfect? No.
But I can say with confidence that most of these would outperform the original SL.
For example, “The Gift That Makes Tails Wag AND Joints Feel Young Again” is a much stronger subject line than “Holiday Gift Guide: Dog Supplements Edition” because it communicates a benefit.
It takes some practice, knowledge, and experience to know which subject line to choose (or which elements to combine), but over time, it will get a lot easier.
There’s also another element to this framework…
A simple way to improve your subject lines
You can also take this SL (or write your own) and let AI rate it based on the 4U’s formula.
For example, let’s take this SL which I rate incredibly high:
“One Button Barista Level Lattes … At 70% Off”
Not too bad, right?
There are no strict rules here, but I’d say anything above 10, and you have a decent subject line on your hands.
If you want to practice, I recommend you try to rate the subject line of this newsletter.
Final tip on subject lines
If you’ve read my Emails that Sell series, you know that I prefer lowercase subject lines.
So Don’t Write Them Like This
Write them just like this
The reason is very simple:
AI will only give you title case subject lines (unless you tell it otherwise).
The easiest way to signal to the reader that the email they’re about to open is from an actual human being is to use lowercase SLs.
But this is just something that I do. Feel free to use this formula however you want, if at all.
Conclusion
Now you know how to write compelling subject lines that get your holiday campaigns (or any types of email campaigns) opened.
Good luck!
