6 Email Subject Line Best Practices for eCommerce in 2023

4 Nov
6 Email Subject Line Best Practices for eCommerce in 2023

Email marketing is crucial to the sales success of your eCommerce company.

Don’t believe it?

Studies show that the average email marketing ROI is 122%, which is significantly higher than any other digital marketing channel. 

But, here’s the thing about email marketing. 

To experience high ROIs, it’s critical to approach email marketing strategically, and it all starts with nailing your subject lines.

In this post, you’ll learn:

  • The importance of getting subject lines right
  • Do’s and don’ts for writing and optimizing your subject lines
  • Examples of winning subject lines and why they work

Pro-tip: Download The Essential Email Copywriting Guide to learn all about email copywriting in detail!

The importance of subject lines in email marketing

If email marketing is the door to more sales, then consider subject lines the doorbell. Subject lines are the loud, enticing, ringing bell that captures attention.

Here’s a look at some of the top stats from email marketing research that show just how critical subject lines are: 

  • Subject lines affect email open rates. 35% of email recipients open emails based on the subject line alone.
  • Subject lines play a role in spam. 69% of email recipients will report an email as spam based on the subject line alone.
  • Personalized subject lines perform well. Studies show emails that include the first name of the recipient in their subject line had a higher clickthrough rate than those that don't.
  • People wake up to subject lines. 58% of adults wake up and immediately check their email.

With over 20% of people checking their email more than five times per day, it’s clear that email plays a huge role in consumers’ everyday lives. And, a surefire way to boost KPIs is to focus on creating engaging subject lines.

Best practices for email subject lines

Now that you know how essential email subject lines are to the success of your email marketing efforts, here are some of the top do’s and don’ts of writing and optimizing your email subject lines.

When you engage in these best practices, you can rest assured you’re writing good subject lines that will resonate with your target audience.

1. Don’t use email curse words; do use verbiage that converts

Email marketing these days is all about personalization. In fact, 83% of consumers are even willing to share their beloved data in exchange for a more personalized experience.

Check out our complete list of email curse words to steer clear from. 

Instead of opting for the most generic and boring subject line, try this:

  • Tell your users exactly what they will get in the email (e.g. discount, story, hot gossip, etc.)
  • Add an emoji (But use caution and only if applicable)
  • Incorporate high converting verbiage into your subject line (e.g, you, special, limited-time, and more)

2. Don’t shoot from the hip; Do test your subject lines

While it’s true there are some proven high-converting subject line words; it’s also true that what your email subscribers will love is 100% relevant to them.

The best way to find out what subject lines get the most opens and clicks from your subscribers is not to guess, it’s to use multivariate testing.

What’s multivariate testing? In short, with the help of a smart email marketing tool like Sendlane, you can test different components and versions of your emails, including subject lines.


3. Do use emojis; but, don’t over-do it

Emojis are cute and study after study shows that people respond positively to emojis. Emojis are particularly powerful in subject lines because they are processed as non-verbal information. In other words, we process emojis as emotional communications. These cute little pics enhance the emotional message marketers are trying to send.


Stats show that 56% of brands using emojis in their email lines had a higher open rate. Marketers have caught onto the trend as one study saw an increase of 775% in emoji use.

Here’s the deal, though, don’t overdo it. There’s a time and a place for emojis use and when used too frequently or in bulk can often cause spam complaints. 

4. Do aim for the subject line number of characters sweet spot; don’t be verbose

It turns out there is an art and a science to writing subject lines. And, how many words you use in your subject lines play a role in open rates.


Image source: Invesp

Research shows the subject line sweet spot is between ~45 characters. Additionally, the more words you use after 5, the lower your open rates get. Keep in mind that the subject line is prime real estate. Some mailbox providers will truncate your subject line if it exceeds their character limits. It makes sense, too, considering many people open emails on mobile devices. 


So, slow down, Shakespeare, and save your deeper thoughts for the content of the email.

5. Don’t let subscribers forget about your offer; do create a sense of urgency

If your subject line comes across with a “don’t worry...just get around to us when you can” type of tone, you can bet your bottom dollar your subscribers will either not open the email, or will forget about it immediately.


You have something awesome to offer. Do yourself a favor and throw words into your subject lines that light a fire under your subscribers. Try words like:

  • Limited-time
  • Today only
  • Exclusive sale
  • Flash sale
  • Holiday promo
  • Black Friday only
  • Cyber Monday only

Stats show that email subject lines with a sense of urgency and exclusivity had a 22% higher open rate.

6. Don’t be spammy; but, do use proven sales words

Did you know that 21% of email recipients report email as spam. Any email that is no longer of interest to the recipient is considered spam. Newsletters that were subscribed, but never opened; eCommerce sites where someone made one purchase over a year ago. These are some examples of spam. So, segment your list of shoppers, and implement a re-engagement email with a subject line that will get your contacts to engage again.

Here are a few examples of re-engagement email subject lines:

  • We’ve Missed You!
  • It’s Been a While
  • 20% off Because We Miss You
  • Do you still want to hear from us?

When trying to gain the attention of the subscribers, the lines can be easily blurred between trying to be witty and being misleading. An unintentional subject line violates CAN SPAM.

Examples of misleading subject lines:

  • Do not pretend the email came from someone you know - "Did I leave my something at your place"
  • Do not use RE: or FWD: - this implies the email was a reply to or  forwarded from a previous conversation
  • Do not make a marketing email look like a transactional email - "Your reservation confirmation" or "About your order"

You know you are a credible eCommerce company, and it’s up to you to convey that message to subscribers. We already talked about email curse words, but it’s important to note that, when it comes to asking for sales, the words you use can be tricky.


The best thing to do is to study words that do and don’t work in emails. When in doubt, use multivariate testing to see what your subscribers like. Once you know, make it a goal to use more powerful sales words in your subject line copy. 

It’s worth it since sales emails have eight times more opens and clicks and can produce six times more money than other types of email.


5 Examples of the best email subject lines from eCommerce retailers (Why they work)

We’ve covered subject line best practices. Now, let’s look at concrete examples of subject lines, from eCommerce retailers that are working, 

1. Curiosity subject lines


Curiosity subject lines can be zany and fun subject lines that are impossible to ignore. They are almost click-bait, but not. Here are some great subject lines that pique curiosity:

  • Jeni’s: “Have a lot of gifts to send?”
  • Casper: “How much do you know about sleep?”
  • Supergood: “Our #1 Most-Asked Question”

As a fun side note, Joanna Wiebe from, used this type of subject line and saw 927% more signups on a pricing page.

2. Self-interest subject lines


Long gone are the days of generic mass emails. Today, successful email marketing is all about catering to the individual. Here are some brands that are crushing it when it comes to catering to individuals:

  • Dollar Shave Club: “We want to give you money.”
  • BaubleBar: “You’re a winner!” 
  • Verizon Wireless: “[Name], your home is missing these easy upgrades.”
  • Chubbies Shorts: “Lemme Teleport You Back to Your Cart. Free Of Charge.” 

3. Urgency subject lines


A sure-fire way to boost open rates and CTR is to foster a sense of urgency. Here are some subject lines that master this strategy:

  • Killington: “Season Pass Savings Disappear Thursday”
  • Poshmark: “Your discounts expire soon.”
  • Wildlist: “Just 52 Spots Left”
  • J. Crew: “Click it or miss it, people: Over 500 styles under $25 is ending!”

4. Exclusive subject lines


Everyone has FOMO and wants their name on the exclusive VIP party list, right? The same logic that applies to wanting to go to an exclusive event applies to email marketing. Here are some examples of excellent subject lines that focus on exclusivity:

  • JustFab: “By Invitation Only: Exclusive Rewards Inside!”
  • Groupon: “Starbucks – By Invite Only” 
  • AMC Theatres: “Hurry, Get Your Tickets to SOLO: A STAR WARS STORY Fan Event!” 
  • Shoes of Prey: “In case you missed these…” 

5. Funny subject lines


People love to laugh at catchy email subject lines. Pique your subscribers' interest with your inner stand-up comedian just like these brands did:

  • Groupon: “Hey… Were You Gonna Delete This?”
  • Free People: “‘Can I please borrow?!’ - everyone you know”
  • Dollar Shave Club: “What to Do When You’re the Sweaty, Smelly Guy at the Gym” 
  • Crate and Barrel: “New planters? Oh, kale yeah.” 

Improve your subject lines now with Sendlane

Writing killer subject lines is one of the best things you can do to improve your email marketing campaigns.

As you start implementing subject line best practices, remember the best way to increase your open rates is to test what works.

Sendlane offers an easy-to-use a/b testing and multivariate testing tool that will help you optimize your subject lines for better results. See for yourself by signing up now for a 60-day free trial!

Please take advantage of our email curse word database and avoid them as a best practice for your email marketing.

Want to learn more about emails? Check out our similar post:

20+ Product Launch Email Subject Lines That Get Results

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