⚡ How 5% Increase in Your Open Rate Leads to 500+ New Leads Using AI Power

Introduction

Studies show that up to 47% of email recipients open emails based on the subject line alone, while 69% mark emails as spam if the subject line feels misleading or spammy. These statistics make one thing clear: mastering subject lines is essential for successful email marketing.

After launching some preview lessons from our AI Mastery AZ course, we received requests to share similar previews from NewsletterAZ. So, as a part of this series, we’ll be offering 5 preview lessons from different sections of NewsletterAZ course, packed with practical tips and examples.

Why Subject Lines Matter So Much

1. Email Overload: People get bombarded with emails daily - newsletters, sales, promotions, updates…you name it. A catchy subject line helps you cut through the noise.

2. High Open Rates = More Engagement: If more people open your emails, you’re getting your message to more people. That means better engagement, more clicks, and more opportunities to build relationships, make sales, or simply keep your audience interested.

3. It’s the Make-or-Break for Success: An email’s performance often boils down to its subject line. A 5% increase in open rates could mean thousands more eyes on your content, depending on your list size. With the right subject line, you’re maximizing every email’s potential.

By the end of this lesson, you’ll know how to:

• Write compelling, eye-catching subject lines that get people curious or excited enough to open your email.

• Avoid common subject line mistakes that could land your email in the spam folder or get it ignored.

• Use AI tools to boost your creativity: Tools like ChatGPT or Jasper can help you brainstorm subject lines that feel fresh and relevant.

So, why invest time in mastering subject lines? Because they’re the single most powerful part of your email, giving you the leverage to turn ordinary content into a high-performing campaign. This lesson will show you exactly how to make every subject line work hard for you.

I. Key Elements of a High-Performing Subject Line Using Open Loop Technique

Open loops are teasers that keep audiences interested and engaged over time. By creating a “gap” in information, you encourage your readers to keep reading to satisfy that curiosity. For example, starting with a subject line like, “Discover the little-known tip that boosts productivity…” opens a loop, making readers want to dive in for answers.

In this section, we’ll break down each type of subject line that incorporates the open loop technique and show you how to use it effectively to boost your engagement and open rates.

1. Keep It Short and Clear

Most people check email on their phones, where subject lines can get cut off. To make sure your entire message is visible, aim for 50 characters or fewer. Shorter subject lines (ideally under 10 words) are quick to read and can pack a punch.

Examples:

• “Last Chance: 50% Off Today Only!”

• “Need Ideas? Here’s Your Guide”

Tip: If you’re struggling to keep it brief, try using AI tools like Claude or ChatGPT or Gemini (your fav model) - or using all at once in USnap. Just ask them to “condense this subject line” or give you three shorter versions. I’ll show you a simple one:

I have an email sending to my users about the new lesson I just added to NewsletterAZ course, I want to make it attractive, engaging. I have several ideas:
1. This is your new lesson in NewsletterAZ course - Grab it now
2. Happy Monday - new week - new lesson - new opportunity
....
But it's too long and can bt cut off on their phone. Let's shorten it while remaining the main idea, you can add some more options for me too.

And here’s the result, because I love the latest reasoning model of OpenAI o1-preview, so I’ll use it in today’s lesson (and it’s in USnap):

Compared to the original ones, these are much better right?

2. Use Power Words to Grab Attention

Power words are like emotional triggers that grab people’s attention. They’re words that create excitement, urgency, curiosity, or a sense of exclusivity. Using them can help your subject line stand out in a crowded inbox and make people feel like they need to open your email right away.

a. Tips for Using Power Words Effectively

• Align the Power Word with Your Message: Not every power word works for every email. If you’re running a limited-time offer, words like “limited,” “hurry,” or “last chance” can create urgency. For helpful content, words like “discover,” “proven,” or “guide” are more suitable. Choose power words that best match your email’s purpose.

• Avoid Overuse: Too many power words can make your email look spammy and reduce trust. One or two strategically placed power words can have more impact than a long list.

b. Power Word Categories and Examples

To make it easier, here are the main categories of power words with examples that match different marketing goals:

b-1. Trust and Comfort Power Words

These words build trust and make readers feel safe, which is ideal for products that require credibility, like financial services or health products.

• Examples: "Certified," "Official," "Backed," "Proven," "Guaranteed"

• Sample Subject Lines:

  • “Proven methods to boost your revenue”

  • “Certified strategies for better results”

b-2. Greed Power Words

These words play on readers' desire for a good deal or financial gain, making them great for discounts, sales, or limited-time offers.

• Examples: "Bargain," "Best," "Big," "Cheap," "Exclusive," "Save"

• Sample Subject Lines:

  • “Biggest sale of the year - save up to 50%!”

  • “Exclusive deal just for our subscribers”

b-3. Curiosity Power Words

Curiosity power words drive clicks by sparking intrigue. These are perfect for content that offers unique tips or hidden insights.

• Examples: "Discover," "Hidden," "Uncover," "Secret," "Bizarre," "Unbelievable"

• Sample Subject Lines:

  • “Discover the secret to better productivity”

  • “Bizarre hack for quick results”

b-4. Vanity Power Words

These words appeal to self-improvement or personal enhancement, which works well in lifestyle, fashion, and personal development.

• Examples: "Amazing," "Bold," "Elegant," "Epic," "Gorgeous," "Strong"

• Sample Subject Lines:

  • “Feel amazing with these quick tips”

  • “Unlock your bold side - here’s how”

b-5. Angry Power Words

While not suitable for every brand, angry power words can highlight frustration and prompt action, especially when addressing common pain points.

• Examples: "Frustrated," "Broke," "Corrupt," "Foul," "Lies," "Liar"

• Sample Subject Lines:

  • “Tired of lies? Here’s the real story”

  • “Say goodbye to frustrating tech issues”

b-6. Lust Power Words

These words appeal to physical attraction or desire, which can be effective in industries like beauty, dating, or fashion.

• Examples: "Alluring," "Beautiful," "Sexy," "Irresistible," "Seductive"

• Sample Subject Lines:

  • “Discover alluring styles for the season”

  • “Irresistible deals just for you”

b-7. Fear Power Words

Fear-based words work when you want to highlight risks or issues that your product or service can solve, especially in security, finance, or health.

• Examples: "Beware," "Hacked," "Dangerous," "Risk," "Warning"

• Sample Subject Lines:

  • “Warning: Don’t make this mistake!”

  • “Is your data at risk? Find out now”

🎁 BONUS: Checklist 150+ Power Words to Boost Conversions

To use this file, try uploading it to o1-preview. Then, give it your subject line idea and ask it to add one of these words in a suitable way, let me show you how:

Let's use these words as inspiration, create a compelling subject line idea for [insert topic here]. Ensure that the subject line is engaging and includes one of these powerful words in a way that feels natural and impactful. The goal is to grab attention and increase open rates, so please consider using emotional or curiosity-driven language

You see, it searched the file and then gave me this subject line with the word 'unlock' integrated.

3. Personalization (Make It About Them)

Personalized subject lines make people feel like the email was created just for them. You can add personal touches to increase open rates and engagement because the content feels more relevant and relatable.

How to Add Personalization to Your Subject Lines:

a. Use Their Name: Including a recipient’s first name in the subject line is one of the simplest and most effective personalization techniques. Seeing their own name grabs attention and gives a sense of exclusivity. Many email platforms, like Mailchimp and Beehiiv, make this easy by adding dynamic fields like “first name.”

• Examples:

  • “Hey [First Name], this is just for you!”

  • “[First Name], we thought you’d love this!”

b. Location-Based Personalization: If you have location data for your subscribers, mentioning their city or region can make your subject line feel more local and relevant. This approach works well for regional events, product launches, or sales in specific areas.

• Examples:

  • “Exclusive deals in [City]—Don’t miss out!”

  • “Hello, [City]! Here’s what’s happening this weekend”

This is also one of our former Newsletter, and take a look at these stats, it’s quite impressive right?

c. Behavioral Personalization: Design your subject lines based on a subscriber’s previous actions. If they clicked on a specific type of product or interacted with certain content, you can reference that in your subject line to increase relevance.

• Examples:

  • “Because you loved [Previous Product]—Check this out!”

  • “More of what you enjoy: New [Product Category] just for you”

d. Using Purchase or Browsing History: If a subscriber has made past purchases or browsed certain items on your site, try referencing those products in the subject line. This makes them feel understood and encourages them to come back for more.

• Examples:

  • “Your favorite [Product Category] is back in stock!”

  • “You left these in your cart, [Name]!”

e. Event-Specific Personalization: Mentioning upcoming events that matter to the subscriber, such as their birthday, anniversary, or even holidays, makes the subject line feel timely and thoughtful.

• Examples:

  • “Happy Birthday, [Name]! Here’s a gift just for you 🎉”

  • “Celebrate your 1-year anniversary with us, [Name]!”

4. Make It Timely and Relevant

When a subject line feels current and connected to something happening now, it’s more likely to catch attention. Relevance, on the other hand, speaks directly to your audience’s interests and needs at that particular moment. Combining the two can make your emails feel “in the moment,” creating a stronger sense of urgency and curiosity.

• Use Seasonal References: Seasonal subject lines, like those connected to holidays or specific times of the year, resonate because they feel immediate and relatable. Subscribers are already in the mindset of that season, so emails that align with it feel natural and inviting.

  • Examples:

    • “Fall essentials for cozy nights in”

    • “Get summer-ready with our top picks!”

    • “New year, new you: Start fresh with our guide”

• Tap Into Upcoming Holidays or Events: People look forward to certain events, like Black Friday, New Year’s, or back-to-school season. Referencing these in your subject lines can boost open rates because they feel highly relevant to what’s on people’s minds.

  • Examples:

    • “Black Friday Sneak Peek: Deals Just for You”

    • “Back-to-school savings you can’t miss!”

    • “Countdown to the New Year: Our Best of 2024”

• Leverage Trends or Current Topics: If there’s a popular trend or timely topic related to your brand, referencing it in your subject line can spark curiosity and make the email feel fresh. Just make sure it’s relevant to your audience and brand.

  • Examples:

    • “Master the latest [Trend] with these quick tips!”

    • “See how [Current Event] affects you”

    • “Everything you need to know about [Trending Topic]”

• Connect to Industry Events or Launches: If there’s an upcoming industry event, product launch, or conference that your audience would find valuable, mention it in your subject line. Even if they’re not attending, they may appreciate content that’s related to it.

  • Examples:

    • “Get ready for [Conference Name]: Must-have tips!”

    • “Insights from [Event/Expo] you can’t miss”

    • “[New Product] is finally here—see what’s new!”

5. Avoid Spam Triggers

Alright, here’s the deal - if your email ends up in the spam folder, it’s as good as invisible. No one’s going to open it, and all your hard work goes down the drain. So, let’s go over some practical ways to keep your emails out of spam and right where you want them: in your audience’s inbox.

• Don’t Shout with ALL CAPS
  When you use ALL CAPS in your subject line, it’s like you’re shouting at your readers and spam filters hate that. You might think it makes your subject line stand out, but it’s more likely to make it look spammy.

  • Examples to Avoid:

    • “LIMITED TIME OFFER - BUY NOW!”

    • “ACT NOW FOR FREE ACCESS!”

  • How to Fix It: Keep it natural and friendly. Instead of “LIMITED TIME OFFER - BUY NOW!” try something like “A limited-time offer just for you.”

• Ease Up on the Punctuation
  I get it, sometimes you want to show excitement, but using too many exclamation points or question marks can make your email look suspicious to spam filters. A good rule? One punctuation mark is enough.

  • Examples to Avoid:

    • “Hurry!!! Limited Stock!!!”

    • “Are you ready for the BEST DEAL???”

  • How to Fix It: Use just one punctuation mark or none at all. A better choice would be, “Hurry - limited stock available.”

• Watch Out for Spammy Words
  Some words are spam magnets. Words like “free,” “discount,” “cash,” and “guarantee” might seem tempting, but spam filters are all too familiar with them. Now, this doesn’t mean you can never use these words, but try to limit them and keep them sounding natural.

  • Examples to Avoid:

    • “100% FREE CASH GIVEAWAY!”

    • “Money-back guarantee on all purchases”

  • How to Fix It: Think of less obvious, friendly alternatives. For example, instead of “100% FREE CASH GIVEAWAY!” you could say, “Enjoy this gift on us.”

• Steer Clear of Over-the-Top Claims
  We’ve all seen those “best deal ever” and “once-in-a-lifetime opportunity” emails that make big promises. But here’s the thing, spam filters see these exaggerated claims all the time, and they know how to spot them. Instead of making it sound like the biggest offer ever, try a more genuine tone.

  • Examples to Avoid:

    • “Best deal EVER - Unbelievable prices!”

    • “Once-in-a-lifetime offer!”

  • How to Fix It: Stick to specifics. Try “Save up to 40% on your favorite products” instead of “Best deal EVER - Unbelievable prices!”

• Beware of Trigger Combinations
  Some words are harmless alone but trigger spam filters when used together, like “buy now” paired with “limited offer.” If you’re using sales language, spread it out across emails instead of piling it into one subject line.

  • Examples to Avoid:

    • “Buy now - Limited offer for a short time!”

    • “Act fast - Free discount just for you!”

  • How to Fix It: Keep it low-key. For example, instead of “Buy now - Limited offer for a short time!” try, “Only a few left - get yours before they’re gone.”

How to Check Your Subject Lines for Spam Triggers:

One of the easiest ways to check if your email might end up in the spam folder is to send a test email to yourself first. If you’re using Beehiiv like in our tutorial, you’re in luck—they have a handy Test Email feature built right in. This feature lets you see how your email will appear in your inbox and gives you a chance to spot any issues before sending it to your entire list.

II. Proven Types of Subject Lines (With AI-Generated Examples)

Let’s look at some popular, effective types of email subject lines. These are proven to capture attention and drive engagement, each leveraging different psychological triggers. Here’s a breakdown, with examples and some tips for creating these types of subject lines.

Note that all examples here are created by o1-preview with “Email marketing specialist” persona. You can also create your own persona in “Persona” section.

1. FOMO (Fear of Missing Out) Email Subject Lines

People can’t stand the thought of missing out on something good. FOMO subject lines create urgency and scarcity, prompting readers to open the email to avoid losing out.

• Common FOMO Words: “urgent,” “limited,” “only,” “today,” “don’t miss out,” “exclusive”

• Examples:

  • "Uh-oh, your discount expires today!"

  • "Only 24 hours left to grab this exclusive deal"

  • "[WEEKEND ONLY] Get this now before it’s gone…"

  • "Don’t miss out on your chance to save big!"

2. Curiosity-Inducing Email Subject Lines

Curiosity drives people to open emails when they feel like they need to find out “the rest of the story.” These subject lines leave just enough mystery that readers can’t resist clicking to learn more.

• Common Curiosity Words: “discover,” “secret,” “mystery,” “surprising,” “what,” “you won’t believe”

• Examples:

  • "You won’t believe what we’ve got for you"

  • "Discover the secret to better productivity"

  • "10 bizarre habits making people wealthier"

  • "This one trick could save you hours"

3. Funny Email Subject Lines

Everyone loves a good laugh, and humor in subject lines can be a refreshing break from more formal messaging. When your subject line makes someone smile or laugh, they’re more likely to open it.

• Common Humor Words: play on words, pop culture references, casual language

• Examples:

  • "Licking your phone never tasted so good"

  • "Need a day at the beach? Just scratch n’ sniff your way to paradise…"

  • "Look what you did, you little jerk…" (from the movie Home Alone)

  • "Try to avoid these 27 people on New Year’s Eve"

4. Vanity Appealing Email Subject Lines

Vanity appeals to people’s desire to feel good about themselves, look better, or improve. This type of subject line often hints at exclusivity, style, or status, making readers feel like they’re part of a special group.

• Common Vanity Words: “look,” “amazing,” “best,” “improve,” “exclusive,” “celebrity”

• Examples:

  • "Your butt will look great in these jeans"

  • "Don’t be caught in last year’s style"

  • "The skincare secrets that celebs swear by"

  • "Your perfect match: Best styles for your personality"

5. Greedy Email Subject Lines

These subject lines tap into the allure of deals, discounts, and special offers. They’re especially effective because most people love a good deal, even if they weren’t looking for one.

• Common Greed Words: “free,” “discount,” “save,” “special offer,” “limited time”. But like I said before, these are easily considered “spam words” in many cases. However, from my experience, sometimes using “Free” is okay now, it can still jump into “Inbox” section.

• Examples:

  • "Flash sale alert! 50% off ends today"

  • "Your exclusive discount inside"

  • "Get the best deals before they’re gone"

  • "Save big on your favorites—today only"

6. Catchy Email Subject Lines

Catchy subject lines grab attention through clever phrasing, making them memorable and hard to ignore. This could be through confident language, a touch of intrigue, or playful language.

• Common Catchy Words: attention-grabbing phrases, direct language, casual tone

• Examples:

  • "Grow your email list 10X faster with these tips"

  • "Steal these email templates…"

  • "A checklist for instant results"

  • "This quick tip is a game-changer"

7. Customer Pain Points Email Subject Lines

This type of subject line addresses a specific pain point or problem, offering a solution right in the subject line. It grabs attention because it feels directly relevant to the reader’s needs.

• Common Pain Point Words: “stop,” “solve,” “get rid of,” “fix,” “save time”

• Examples:

  • "Stop wasting money on overpriced ink"

  • "Struggling with productivity? Try this."

  • "Your kitchen’s best friend: Space-saving ideas"

  • "Save time with this simple trick"

8. Retargeting Email Subject Lines

Retargeting subject lines are used to bring people back to complete an action they didn’t finish, like checking out or signing up. These lines are often more direct and aim to remind or nudge the subscriber back to the desired action.

• Common Retargeting Words: “miss,” “forgot,” “didn’t complete,” “come back,” “your cart”

• Examples:

  • "Did you forget something? Complete your order!"

  • "The price dropped on items in your cart"

  • "Your free trial ends soon—don’t miss out!"

  • "Still thinking it over? Here’s a special offer"

9. Personalized Email Subject Lines

Personalized subject lines, especially those using the recipient’s name or specific preferences, make emails feel more tailored. This creates a sense of exclusivity and increases the likelihood of opens.

• Common Personalization Words: “your,” “for you,” recipient’s name, tailored content

• Examples:

  • "Hey [Name], your hand-picked offers are here"

  • "[Name], your exclusive access is waiting"

  • "Just for you, [Name]: Get a sneak peek!"

  • "Your personal guide to [goal]"

10. Straightforward Email Subject Lines

Straightforward subject lines are often the best choice when the content of your email speaks for itself. No fluff—just a clear, direct description of what’s inside.

• Common Straightforward Words: “today’s update,” “newsletter,” “weekly tips,” “special offer,” “product update”

• Examples:

  • "Weekly Newsletter: Top articles for you"

  • "Today’s exclusive deal—don’t miss out"

  • "New arrivals just dropped!"

  • "Update on your recent purchase"

🎁 TODAY’S GIFT: 100+ Ready-to-Use Subject Lines – Just Copy and Send!

III. Advanced Tips for Subject Line Success

The goal here is to make your subject lines work harder for you by adding subtle elements that make a big difference.

1. Use A/B Testing to Find What Resonates

A/B testing, or split testing, is a powerful way to see what works best for your audience. It involves creating two (or more) variations of a subject line and sending each to a small portion of your audience. Whichever subject line performs better is sent to the rest of the list.

So you may know (or we’ll definitely let you know that Beehiiv has built-in A/B testing features. They let you track metrics like open rates and clicks so you can see which subject lines perform best👇 And we do this almost everyday for AI Fire Newsletter.

Pro Tips for Successful A/B Testing in Beehiiv

• Focus on Small, Single Changes: When A/B testing, only test one element at a time (like a word or tone change) to understand exactly what makes a difference.

• Track and Record Results: Keep a log of your Beehiiv A/B test results, noting which types of subject lines consistently perform best. This will give you a valuable reference point over time.

• Run Tests Regularly: A/B testing isn’t a one-time task. Regular testing helps you adapt to changing audience preferences, keeping your subject lines fresh and effective.

2. Leverage AI Tools for Suggestions and Optimization

AI tools can be your best friends when it comes to crafting engaging, optimized subject lines. These tools can help you brainstorm ideas, fine-tune language, predict performance, and even A/B test for the best results.

So far in this lesson, I used o1-preview with pre-made specific persona in USnap to show you examples and you can do too.

If you’re stuck or need a starting point, they can provide multiple variations of a subject line based on a few prompts. Begin by asking AI tools for a wide range of ideas. Once you have a list, narrow down to those that feel right for your brand, and use optimization tools to make final tweaks. AI tools can generate ideas in various tones (casual, formal, playful). Use this flexibility to match your brand voice or adapt to different segments of your audience.

Example Workflow Using AI Tools for a Campaign

Let’s say you’re creating an email campaign to announce a special promotion. Here’s how you might use AI tools step-by-step:

1. Brainstorm with o1-preview: Start with a prompt like “Suggest FOMO-driven subject lines for a 24-hour sale” and get several ideas.

2. Optimize with Anyword: Pick the best suggestions from GPT and plug them into Anyword. See if Anyword recommends different wording to improve engagement or increase urgency.

   

3. Predict with Jacquard: Enter the top 2-3 variations into Jacquard to get a predicted engagement score for each. Choose the highest-scoring one for your final subject line.

   

Conclusion and Homework

Mastering subject lines takes practice, but every little improvement you make can have a big impact on your email performance. A well-crafted subject line is more than just a way to introduce your email - it’s a gateway to engagement, clicks, and conversions.

By applying what you’ve learned about power words, personalization, curiosity, and even using AI for optimization, you can make your subject lines irresistible.

Remember: Subject lines are your first impression. They set the tone and decide whether your email gets opened or overlooked. Keep experimenting with different types and don’t be afraid to mix things up based on your audience and goals.

Homework: Putting It All Into Practice: Now it’s time to take what you’ve learned and put it to the test. Write three unique subject lines for an upcoming email campaign, each using a different technique you learned in this lesson:

• One curiosity-driven subject line

• One vanity appealing subject line

• One FOMO-driven subject line

Keep practicing, and soon you’ll be a pro at grabbing attention right from the inbox. Bye for now, and good luck with your first campaign!