What if the latest AI model could write sales emails sharper, faster, and more persuasive than you ever imagined? What if the days of bland, robotic copy were over, and AI could finally deliver the kind of punchy, sales-driving messages you need to fill your courses and coaching programs?

That’s the big question hanging over the launch of ChatGPT 5, and after testing it head-to-head against GPT-4o, the results may surprise you. This isn’t just another shiny new tool update.

This is about whether GPT-5 can actually sell. Because at the end of the day, that’s what matters in email marketing.

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From Hype to Reality: Is ChatGPT 5 an Upgrade?

ChatGPT 5 launched on August 7 with plenty of hype. OpenAI promised PhD-level intelligence, multimodal support, and, most importantly for marketers, a system that automatically picks the right model for the job.

Sounds impressive. But does it actually deliver when it comes to writing emails that convert?

The truth is, my first test was a disaster. The early version of GPT-5 was, to put it bluntly, a complete mess. The output was bland, awkward, and nowhere near ready to replace GPT-4o for real marketing tasks.

But after a major fix from OpenAI, I decided to give it a second chance, and this time, I put it through a rigorous 17-point scoring system to see if it could really compete.

The Test: Email Marketing Showdown

To keep things fair, I gave both GPT-4o and GPT-5 the exact same challenge:

*Write a 200-word direct response email to online coaches struggling to sell their courses. The email should promote a free live class titled *‘How I Increased Sales from $27,000 to $500,000 Without Changing My Offer.’”

Both models had to write subject lines, hooks, and full email copy designed to get coaches to register for the class happening on Tuesday.

Then, I scored each output across 17 critical areas of email copywriting: from attention-grabbing subject lines to clarity, emotional impact, call-to-action effectiveness, and more.

Round One: Subject Lines

• GPT-4o:
  “From $27k to $500k Without Changing Your Offer”

Simple, direct, and very clickable. Almost perfect, but a little stiff. Score: 9/10.

• GPT-5:
  “From $27k to $500k Without Changing Your Offer”

Nearly the same, but longer and clunkier, with extra punctuation that made it less mobile-friendly. Score: 7/10.

Winner: GPT-4o.

Round Two: The Hook

• GPT-4o:
  “Hey, if your online course isn’t selling like it should — but you know it’s good…”

This felt natural and spoke directly to the reader’s frustrations. Score: 8/10.

• GPT-5:
  “Most coaches think the only way to make more sales is…”

This version leaned into a “you’re wrong” approach, which risks alienating readers. Score: 6/10.

Winner: GPT-4o.

Round Three: The Body Copy

Here’s where things got interesting.

• GPT-4o kept it short and punchy, emphasizing that coaches don’t need a new offer, more leads, or a big funnel, just better emails. But it sometimes felt rushed, and repeated itself with the classic “three-punch” list. Score: 7/10.
  

• GPT-5 was smoother and easier to read. The sentences flowed better, and the structure felt more natural. It also used urgency (“Seats are limited”) effectively. The downside? It leaned on the “you’re doing it wrong, I’m doing it right” tone, which can rub people the wrong way. Score: 10/10 for readability, 7/10 for fluff.
  

Winner: GPT-5.

Round Four: Call to Action

Both models kept things clean with one main CTA: “Save your seat for Tuesday.”

• GPT-4o’s was solid but buried at the end. Score: 8/10.
  
• GPT-5’s included urgency and benefits, making it slightly more compelling. Score: 8.5/10.

Winner: GPT-5.

Round Five: Overall Structure & Layout

• GPT-4o: Short paragraphs, but looked choppy, almost like a school poem. Score: 7/10.
  
• GPT-5: Varied sentence lengths and smoother flow, much closer to natural human writing. Score: 9/10.

Winner: GPT-5.

The Final Tally

After scoring all 17 criteria, here’s how the results stacked up:

• GPT-4o Final Score: 134/170
  
• GPT-5 Final Score: 139.5/170
  

It wasn’t a blowout, but GPT-5 came out ahead, proving itself the stronger tool for writing persuasive, readable sales emails.

Why GPT-5 Wins

The biggest breakthrough isn’t just the slightly higher score. It’s how GPT-5 decides which model to use for each task.

Instead of forcing you to choose between “GPT-4o, GPT-3.5, or Mini,” GPT-5 makes the decision for you. It automatically routes your request to the model best suited for the job.

For marketers, this is a game-changer. You no longer need to guess which engine will give you the best output. Just give GPT-5 the prompt, and it handles the rest.

That’s not only more efficient, it’s smarter copy, with less effort from you.

The Big Takeaway for Email Marketers

Here’s the truth: GPT-5 isn’t perfect.

It sometimes slips into self-congratulatory tones (“Look how smart I am!”) and can overcomplicate simple subject lines. But when it comes to readability, flow, and persuasion, it beats GPT-4o by a clear margin.

If you’re writing emails to sell your courses or coaching programs, GPT-5 is finally a model you can trust to give you a solid first draft that saves you time, sparks ideas, and gets closer to ready-to-send than ever before.

Conclusion: Should You Use GPT-5 for Emails?

Absolutely.

With better structure, smoother copy, and the ability to auto-select the right model, GPT-5 proves it’s ready to step up for email marketers.

No, it won’t replace your judgment, creativity, or knowledge of your audience. But as a powerful partner in your writing process, it’s a massive upgrade.

The bottom line?
If you want emails that sell, GPT-5 is finally the tool that can help you write them faster, stronger, and sharper than before.

And as OpenAI continues to refine it, the gap between GPT-5 and every model before it is only going to grow.

So test it. Tweak it. Push it. And watch how it transforms the way you sell with email.

Related episodes

The Affiliate Marketing Playbook: How to Make Sales Without Annoying Your List

Webinars That Sell: Insider Secrets from Jason Fladlien!

How to Use Storytelling in Your Emails to Get a 22% Higher Open Rate

FREE list of the top 10 books to improve your email marketing

If you want to write better emails, come up with better content, and move your readers to click and buy, here's how. We put together this list of our Top 10 most highly recommended books that will improve all areas of your email marketing (including some underground treasures that we happened upon, which have been game-changing for us). Grab your FREE list here. 

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If you want to chat about how you can maximise the value of your email list and make more money from every subscriber, we can help! We know your business is different, so come and hang out in our FREE Facebook group, the Email Marketing Show Community for Course Creators and Coaches. We share a lot of training and resources, and you can talk about what you're up to.

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