Standing out in the inbox starts with a compelling subject line. This article shares proven best practices, real-world examples, and practical tips to help you craft high-performing subject lines that boost open rates and drive more revenue.
Nearly 392 billion emails are being sent every day. Yet sadly, a huge percentage of those messages – no matter how helpful they are – never get a chance to be opened. Because without an effective, persuasive, attention-grabbing subject line, your marketing emails might get lost in crowded inboxes. And no opens means no clicks – and ultimately no revenue.
In this article, we’ve outlined some of the best practices for crafting high-performing email subject lines based on research and insights from Maropost’s email marketing experts to help you improve the success of your email marketing strategy. On top of that, we’ve provided examples of effective email subject lines to inspire your campaigns and help you drive more opens.
Here are some of the tried-and-true email subject lines best practices for increasing email open rates based on research and Maropost’s expert insights:
When it comes to email subject lines, personalization is the key to improving your email marketing open rates. Personalized subject lines always resonate with subscribers more than generic ones because they make your emails feel more relevant to them.
In fact, Campaign Monitor reports that personalized subject lines can boost email open rates by as much as 26%. However, Gartner’s research revealed that only 31% of brands use personalized subject lines in their email campaigns.
For most brands, “personalization” in a subject line means simply using the subscriber’s first name. With a professional email marketing platform like Maropost Marketing Cloud, you can use Liquid Scripting for more advanced subject line personalization that goes beyond subscribers’ names. With Liquid Scripting, you can personalize subject lines based on:
Browsing history: “Still thinking about the Samsung Galaxy 26?”
Cart activity: “Don’t forget your Apple AirPods Pro, Oliva 🎧”
Recent purchases: "What score would you give to your new HP OmniBook?"
Loyalty level: "Congratulations, David! You've just achieved Silver status"
Personal milestones: “Can You Believe it’s Been a Year?”
|
"The effectiveness of subject line personalization is unchanged. But what has changed is the type of personalization. Adding someone's first name doesn't do anything. They already know who they are. But adding what they've recently done is the attention-grabber." – Manny Ju, Director of Product, Maropost |
Recommended reading: Personalized email marketing: top 5 strategies for 2026
According to data from GetResponse, emails achieve the highest open rates (43.38%) when subject lines fall within the 61–70 character range. Klaviyo’s research also revealed that subscribers are less likely to open emails with longer subject lines. On average, brands use subject lines that are about 7 words (including emojis), and these tend to achieve open rates close to 30%.
At the same time, mobile inboxes only display the first 33 to 50 characters of a subject line, so if most of your opens happen on mobile, keep that limit in mind.
While adding punctuation marks and emojis in subject lines is a standard practice in email marketing nowadays, the excessive use of those can actually do more harm than good. Too many punctuation marks and special characters can make your emails look like spam.
Mailchimp recommends using punctuation sparingly in subject lines, with no more than three punctuation marks and a single emoji per subject line.
An email preheader is a short summary text that appears below the subject line in the inbox preview. It gives your subscribers a better idea of what’s inside the message before they open it. And in many cases, this powerful line of text can be the deciding factor in whether someone opens your email or skips it.
Emails that include preheader text tend to perform better, with GetResponse reporting average open rates of 44.67%, compared to 39.28% when no preheader is used.
Ideally, preheader text should fall between 40 and 130 characters so it displays properly on both mobile and desktop. Place the most important information at the beginning, so even if the text does get cut off on mobile devices, your main message still comes through.
For an email to be opened, it needs to land in the inbox in the first place. However, using certain words and elements in your subject lines often triggers spam filters, hurting your email deliverability and causing your emails to be sent straight to spam folders, where they almost never get a chance to be seen.
Here’s what you shouldn’t be using in your email subject lines to avoid spam filters:
Aggressive punctuation (e.g., multiple exclamation marks !!!)
ALL CAPS (“BUY NOW”, “LIMITED TIME OFFER”)
Multiple emojis (especially when they are used to replace words)
Excessive symbols (e.g., dollar signs $$$ and characters like %, @, #)
Spam-trigger words (100% free, Guaranteed, Risk-free, Act immediately)
Exaggerated claims (“Lose 20 lbs in 7 days!!!”, “Designer bags for only $1.00!”)
Weird spacing or special fonts (those are a one-way ticket to the spam folder)
While you shouldn’t rely entirely on AI to write your subject lines, it can be incredibly helpful in certain situations, like:
When you just don’t really know where to start
When you’re stuck creatively
When you need multiple variations quickly (e.g., for A/B testing)
When you need personalization at scale
Fortunately, many email marketing automation platforms already include built-in gen AI tools to help marketers craft high-performing subject lines and email copy to speed up campaign creation.
If you’re looking for specific email subject line ideas to use on your campaigns, we’ve collected some of the great examples of high-performing subject lines from real brands to inspire you.
Welcome to GIR – Where Culinary Dreams Take Shape (GIR)
Your dog’s best life begins here (Biome9)
Welcome! Enjoy 10% OFF Your First Order ☕ (Wandering Bear Coffee)
Welcome to S'well! Your offer is waiting (S’well)
Thanks….you’re all signed up to receive Best Buy e-mails (BestBuy)
Welcome to the Cosmetics Revolution 🫧 (Lush)
[Name], don't forget this item: Mango Small crossbody bag! (Mango)
Lemme Teleport You Back to Your Cart. Free Of Charge. (Chubbies Shorts)
Your shopping bag misses you. (Dote Shopping)
Your basket is having abandonment issues…:( (Jack Mills)
Need more time? Your ebike is still here (for now). (Aventon)
Your tea is right where you left it. (Brew Tea Co)
Recommended reading: Cart abandonment emails: best practices and real examples
[Name], get 15% off your next trip (Booking.com)
Savings Continue: 20% Off Everything ☕️ (FlavCity)
Loom’s Annual Rug Sale Starts Tuesday! (Loom)
You’re Invited: Memorial Day Sale Early Access (SAYSO)
Lucky Yogi! Get 40% off 2 Lyka orders (Lyka)
Someone as awesome as you deserves awesome deals. (Roku)
Last day: Up to 30% off top picks (H&M)
Uh-oh, your prescription is expiring (Warby Parker)
Shirts for $39 ends at midnight (Charles Tyrwhitt)
Experience the FW22 Collection at 9 am EST (Woolrich)
Your Winter Sale early access ends today! ⏰ (Mammut)
⌛Final Hours!⌛ Save 50% on your first order! (Sundays)
[NAME], have you tried our NEW Hydra-Peptide Lip Butter? (NUDESTIX)
Hey, did you forget to open this? (Dollar Shave Club)
Come Back This Winter With an Exclusive Deal, [Name] (Vail Resorts)
Happy CleanMyMac-versary! Grab your discount 🎁 (MacPaw)
[First Name], check out these hand-picked looks (Guess)
Your birthday gift is still available (get 15% off) (Adidas)
Early Access to Black Friday is Here! (Yolele)
Make your Christmas wish come true! 🎄✨(Travelodge)
Don’t Panic — Valentine’s Day Is Saved 💘 (LINE FRIENDS)
Don’t Ghost Yourself: Order by Tomorrow! 👻 (Rebel Rabbit)
Eggcelent Greetings & Gifts for Easter (Rifle Paper Co)
Father’s Day gifting made simple (Mulberry)
Maropost Marketing Cloud has all the tools and capabilities you need to create highly personalized, high-performing subject lines that can boost your email open rates and improve campaign performance. That includes:
Liquid scripting for advanced subject line personalization: Maropost Marketing Cloud enables you to personalize your email subject lines on a deeper level. With Liquid scripting, you can dynamically pull in contact data, apply formatting filters, and conditional IF/THEN logic to adjust messaging or display fallback text when information is missing. This helps you create subject lines that feel more relevant to each subscriber.
A/B testing tools for optimizing open rates: With A/B testing campaigns, you can easily test multiple variations of subject lines and preheaders before sending your campaign to your full audience. Choosing the Highest Open Rate as your winning criteria ensures that the subject line that gets the most opens in the test group will automatically be sent to the rest of your audience.
eRFM insights for granular segmentation and deeper personalization: Email personalization shouldn’t be limited by subscribers’ names in the subject line. Maropost’s eRFM reporting lets you segment your customers by both purchase history and real-time engagement behavior so you can create more granular customer segments and send more targeted, personalized email campaigns.
Book a demo now to see the Maropost Marketing Cloud in action and learn how it can support your email marketing needs and help you run successful, personalized email marketing campaigns that engage and convert.