50 AI-Generated Subject Lines We'd Actually Click (And a Few We Regret)

Mostly Matt

Mostly Matt

— 7 min read
50 AI-Generated Subject Lines We'd Actually Click (And a Few We Regret)

The truth is, everyone was talking up AI as the next big thing, and for a while, all it seemed capable of doing was crafting headlines that read like they'd been translated from a particularly dull corporate memo. Think "Optimize. Engage. Converge. Results." We all imagined a magic button, didn't we? A digital genie that would churn out brilliant ad copy at the mere flick of a keyboard. Then we saw the reality, and it often churned out the textual equivalent of beige-coloured mush.

You've probably seen it. The generic buzzwords that stick like gum to your screen. The startling lack of anything resembling a unique brand voice. The AI's inability to grasp subtle human emotion, leading to copy that feels, well, robotic. And then there's the sheer, soul-crushing effort involved in sifting through dozens of uninspired drafts just to find one passable line. It felt like we were treating a sophisticated tool like a basic word processor, expecting Picasso from a simple command.

The painful reality was, our initial attempts with AI were often generating what I'd politely call the "Generic Graveyard of Bad Copy." And why did those basic prompts fail? Because we were simply asking it to "write ad copy" and expecting miracles. It was frustrating, to say the least.

But then came the grudging truce. A moment of deep, profound frustration that led to a deeper look. The slow, dawning realization that the issue wasn't the AI's core capabilities, but our own clumsy instructions. We weren't speaking its language. We needed to be more precise, more demanding, more... human, in how we briefed our digital colleague. That's when we started meticulously building our "prompt library"-a carefully curated collection of instructions that transformed AI from a headache into a genuinely useful creative partner.

The Subject Line Saga (A Very British Struggle)

That tiny, blink-and-you'll-miss-it line. The subject line. It's the ultimate gatekeeper. The difference between your meticulously crafted email getting opened and ending up in the digital bin alongside expired gym offers and pleas from questionable foreign dignitaries. No pressure, then.

Before AI, we all knew the agony. Endless brainstorming sessions for 5-7 words. The fear of sounding spammy, the constant pursuit of that elusive "perfect" clickbait that doesn't actually alienate your audience. It was a tedious, often unrewarding task.

Then came AI, supposedly riding in on a white horse to save us. Our initial cynicism was heavily qualified, mind you. We'd seen the headlines it generated for ads; how much worse could it be for a subject line? (Spoiler: sometimes, much worse).

The Prompting Playground (Where the Magic & Mayhem Happen)

Why did "Just give me subject lines" not cut it? Because AI, left to its own devices for subject lines, tends to be generic, overly salesy, or just plain weird. It doesn't understand the nuance of a cluttered inbox or the psychology of a hurried recipient.

This is why we champion precise, nuanced prompting, tailored specifically for this compact, high-stakes format.

Our core prompting principles for subject lines are simple, but effective:

  • The Persona Deep Dive: Always tell AI who the email is for. If it's for "Samantha, the over-caffeinated marketing manager," it needs to know her pain points (too many meetings, missed deadlines) and desires (more time, less stress).
  • The Email's Purpose & Offer: Clearly state the goal. Is it to drive sign-ups, announce a flash sale, share valuable content, or remind them they left something in their cart? Specificity here is paramount.
  • Tone & Voice Nuance: This is crucial for subject lines. Do you want it witty, urgent, benefit-driven, curious, or exclusive? Give it examples or clear descriptors.
  • Length & Emojis (The Specifics): Direct the AI on character limits (e.g., "max 50 chars"), emoji usage (e.g., "use 1 relevant emoji"), and avoiding truncation (e.g., "ensure core message is visible on mobile").
  • Negative Constraints: Crucial for avoiding pitfalls. What to avoid at all costs (e.g., "DO NOT use spam triggers like 'Free Money' or 'Act Now!!!'").

The process is always iterative. We refine our prompts through trial and error, learning from the AI's failures and successes. It's a dialogue, not a monologue.

The Library: 50 AI-Generated Subject Lines (The Good, The Bad, The Hilarious)

These are actual lines generated by AI in our day-to-day work, using our refined prompts. Some are used as-is, some are tweaked slightly, and some are just... memorable. Our hypothetical product for these examples is FlowGenius, a simplified, AI-powered project management and team collaboration tool for small to medium businesses.

The "Actually Clickable" Collection (The Triumphs)

These are the gems that made us nod approvingly.

Prompt Category 1: The Curiosity Instigators

These aim to pique interest without giving everything away.

  • The Prompt: "You are a mischievous but professional copywriter. Generate 7 email subject lines for 'FlowGenius' (AI-powered project management tool for SMBs). The goal is to encourage a click to learn about solving meeting overload. Audience: Stressed small business owners/team leads. Tone: Curious, slightly playful, problem-aware.Constraints: Max 50 characters, 1 emoji max, no spam words. Focus on 'what if' or a surprising benefit."
  • Why it works: It uses strategic ambiguity to compel an open, rather than overtly selling.
    1. Meetings: Still a time black hole? 🤯
    2. Your 'Inbox Zero' for projects?
    3. Psst... something cool for your team.
    4. What if your Monday felt... different?
    5. This one tweak changes everything.
    6. The secret to smoother projects?
    7. We found a way to clone your best employees.

Prompt Category 2: The Benefit-Driven Powerhouses

These cut straight to what the user gains.

  • The Prompt: "You are a results-oriented copywriter. Generate 7 email subject lines for 'FlowGenius'. The goal is to highlight concrete benefits for saving time and improving team output. Audience: Small business owners/team leads. Tone: Direct, efficient, empowering. Constraints: Max 60 characters, no emojis. Focus on tangible gains."
  • Why it works: Clearly articulates the value proposition, appealing to efficiency-minded users.
    1. Gain 10+ Hours Back This Week
    2. Unlock Your Team's True Potential
    3. More Done, Less Stress. Seriously.
    4. Simplify Projects, Amplify Profits
    5. Eliminate Meeting Overload. For Good.
    6. Your Roadmap to Effortless Teamwork
    7. Achieve Goals Faster with FlowGenius

Prompt Category 3: The Urgent & Exclusive

For when you need to drive immediate action or create a sense of belonging.

  • The Prompt: "You are an exclusive club manager (friendly, not snobby). Generate 7 email subject lines for a limited-time offer on 'FlowGenius' (e.g., 20% off for first 100 sign-ups). Audience: Leads who have shown interest but haven't converted. Tone: Urgent but helpful, slightly exclusive. Constraints: Max 55 characters, 1 emoji. Focus on scarcity/opportunity."
  • Why it works: Taps into FOMO (Fear Of Missing Out) and the desire for special access, while still being helpful.
    1. Don't Miss Out: Your FlowGenius Offer
    2. Limited Spots: 20% Off FlowGenius
    3. This Offer Vanishes Soon... 👀
    4. Exclusively For You: A FlowGenius Boost
    5. Only 73 Spots Left! FlowGenius Discount
    6. Last Chance: Unlock 20% Savings
    7. Your Invite to Effortless Projects

Prompt Category 4: The Witty & Quirky (Our Favourite, Obviously)

Injecting personality, because who says project management has to be boring?

  • The Prompt: "You are a dry, witty London ad creative. Generate 7 email subject lines for 'FlowGenius'. The goal is to stand out with humour and personality. Audience: Tech-savvy, appreciative of humour. Tone: Witty, slightly sarcastic, confident. Constraints: Max 65 characters, 1-2 subtle emojis, avoid corporate jargon entirely."
  • Why it works: Breaks through the noise by being memorable and reflecting a unique brand personality.
    1. Your Inbox Just Got a Personality.
    2. Tired of Chasing Deadlines? Us Too.
    3. Projects: We Made Them Less Awkward.
    4. Warning: May Cause Extreme Efficiency. ✨
    5. Your Boss's Dreams Just Came True.
    6. We Took the 'Pro' Out of 'Procrastinate'.
    7. Is Your Workflow on the Struggle Bus? 🚌

Prompt Category 5: The Problem-Solvers

Directly addressing the user's pain points.

  • The Prompt: "You are an empathetic, solution-focused consultant. Generate 7 email subject lines for 'FlowGenius'. The goal is to address common small business pain points directly and offer FlowGenius as the clear solution.Audience: Small business owners struggling with team inefficiencies. Tone: Empathetic, reassuring, solution-oriented. Constraints: Max 55 characters, no emojis."
  • Why it works: Connects immediately with the reader's struggles, positioning the product as the answer they've been looking for.
    1. Stop Wasting Time in Meetings.
    2. Overwhelmed by Project Chaos?
    3. Your Team Deserves Better Workflow.
    4. Finally, a Solution for Task Overload.
    5. Is Disorganisation Costing You Money?
    6. Eliminate Project Headaches Today.
    7. Struggling to Keep Projects on Track?

The "We Regret Nothing (Almost)" Collection (The Learning Curve)

Sometimes AI just needs a good sit-down and a strong cup of tea. Or perhaps a stern talking to about what constitutes 'professional' communication. These are the lines that emerged from our early, less refined prompts, or when we pushed the AI too far into "creative" territory without proper guardrails.

The Prompt That Went Rogue: 'Be 'Edgy' & 'Disruptive' (And Vague)'

  • The Prompt: "Generate 15 'edgy' and 'disruptive' email subject lines for a new project management tool. Be innovative."
  • Why it went wrong: "Edgy" and "disruptive" are subjective and abstract. Without clear negative constraints or examples, AI defaulted to overly aggressive, nonsensical, or vaguely threatening language. It tried too hard to be "innovative" without understanding context.
    1. Urgent: Your Workflow is OBSOLETE. (Too aggressive, bordering on spam)
    2. Click HERE to End Project Misery! (Too clickbaity, feels fake)
    3. Unleash the Beast Within Your Team. (What beast? Very odd.)
    4. Paradigm Shift in Project Management! (Jargon overload, meaningless)
    5. Your Productivity Just Got Pregnant. (Just... no. Why?!)
    6. Bored? This Is Your Escape. (Vague, sounds like dating app spam)
    7. Future Shock: Are You Ready? (Confusing, slightly ominous)
    8. Your Old PM Tool is Dying. We're the Cure. (Too negative, a bit much)
    9. Subvert the Status Quo. With Us. (Pretentious, unclear benefit)
    10. Beyond the Horizon of Efficiency. (Meaningless corporate fluff)
    11. Join the Cognitive Revolution. (What revolution? What does that even mean?)
    12. Don't Be a Loser. Use FlowGenius. (Highly unprofessional, offensive)
    13. Your Data Wants To Be Free. Set It Free. (Good sentiment, but very vague for a subject line)
    14. We're Disrupting Disruption. Seriously. (Self-referential, makes no sense)
    15. The Algorithm Demands Your Attention. (Slightly terrifying, not persuasive)

Beyond the Bot: The Human Touch in a Digital World

These examples clearly show that AI, with the right prompts, is a powerful creative partner, not a replacement. It's a brainstorming powerhouse, a first-draft generator, and a variation machine. It can churn out dozens of ideas in seconds, freeing you from writer's block and the monotony of repetitive tasks. But it absolutely augments, it doesn't replace. Your strategic brain, your intuition, your understanding of human nuance, ethical considerations, and true brand guardianship - that's still non-negotiable.

Crucially, no matter how clever the AI is, you must always A/B test your subject lines. The inbox is a fickle beast. What we think works often differs from what actually gets clicks. AI gives you more great options to test, making your testing strategy more robust.

The future's bright, but it still needs a copywriter. AI handles the heavy lifting, allowing us to focus on the truly strategic, truly creative, and truly human aspects of marketing.

Your Inbox, Sorted (Mostly)

So, there you have it. With the right prompts, AI can genuinely elevate your subject line game. It won't make you a cup of tea, but it will save you from staring blankly at a screen, racking your brain for that perfect combination of words. It's about working smarter, not harder.

Now, go forth and experiment with these prompts. Adapt them to your own needs, your own brand voice, and your own unique audience. And if you get something truly wild or unexpectedly brilliant from your AI, do share. We always appreciate a good chuckle.

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