To open or not to open, that is the question.

A subject line is the first thing subscribers will see when your emails land in their inbox.

When crafted carefully, a subject line can push email subscribers to open marketing emails and bring them one step closer to a conversion.

But solid subject line ideas aren’t always easy to come by.

In this post, we’ve compiled a few subject line testing ideas that email marketers can use in their next campaign.

The importance of subject line testing

Email subject line testing is the process of testing different subject line ideas to determine which one is best at engaging your audience.

A subject line test is a quick way to add value and increase open rates for your future email campaigns. Depending on your email service provider (ESP), you too can implement an A/B subject line test in just a few clicks.

Many ESPs also allow you to test a percentage of your email segment and send the winner at a later time to the remaining audience. How subject lines perform can vary significantly from brand to brand. So, test what works for your audience. We’ve compiled a few A/B subject line test ideas you can implement in less than five minutes.

Emojis vs. no emojis

I’d be shocked if you told me you haven’t seen a subject line with an emoji in your inbox before. But how does using one compare to not using one? This might be something you’ll want to test for your brand to switch things up. For your test, make sure using an emoji makes sense and is appropriate for your brand.

Here are a few emoji email subject lines we’ve seen in the MailCharts app the past few weeks to inspire you: (Note the personalized subject line in example one. What a power move!)

  • 🎁 Pick your gifts, Brenda
  • Find The Perfect Gift 💞 Mother’s Day Gift Guide
  • ⚡Sunday Steal!!! ⚡
  • Show your hubby he’s special 🤵❤️
  • Elegant in emerald💚
  • Because 🏠 is the new office
  • Be inspired by animals in art 🐯 🐘 🐦
  • Stuck indoors? Surf our sale section 🌊
  • Can you solve this dino-mite puzzle?! 🦖🧠
  • Tik Tok…Time Is Running Out! ⏰
  • ⏰You snooze, you lose.
  • Refresh Your Spring Beauty Routine 💐

Did you know? You can use the MailCharts advanced search feature to search exclusively for emails that incorporate an emoji in the subject line:

Advanced search emojis screencap 300x155

Short vs. long subject lines

Typically, shorter email subject lines (60 characters or fewer) have higher open rates than long subject lines. However, this might not be the case for all brands. It’s worth experimenting with your brand’s audience on the length of the subject line. We recently wrote a blog post on short subject lines that provides some ideas.

Here are a few subject line examples we’ve seen in the past few weeks for subject lines that fall within the ‘optimal subject line length’ category:

  • Don’t forget about your birthday treat on us!
  • The pieces you’ll wear on rotation
  • Love the color Blue? Check out our favorites…
  • How’s Your Weekend Going?
  • Big splash: 50% off all swim tonight only
  • Hurry, but Don’t Worry: 10% Off Ends Tomorrow

Did you know? With MailCharts, you can use the advanced search feature to search by subject line length:

Advanced search subject line screencap 300x149

Question vs. statement subject lines

Does a question or statement perform better in the inbox? It’s easy to frame your already existing statement subject lines into questions and vice versa.

Here are a few question email subject lines ideas we’ve been seeing in the MailCharts app:

  • Need Some Help Getting Ready For Your Next Project?
  • Who doesn’t love a floral-print dress?
  • Ready to take your style to new heights?
  • Looking for ways to help healthcare heroes? We got one!
  • Want A Special Birthday Surprise?
  • Looking for everyday supplies?
  • Sick Of Your Sweatpants Yet?
  • Did you check out this sale yet?
  • Have you heard? Select styles up to 50% off!
  • Hi! Remember Us? 🖤
  • Need an excuse to treat yourself? 👉👉👉
  • Looking to Lounge?


Urgency vs. savings subject lines

Are your customers more worried about saving money or missing out on a great deal? This is a great test for retailers to see which one performs better with subscribers. It’s also a great way to shake up your subject line ideas if you tend to use one type over and over.

  • Savings subject lines we love:

    • Buy This Shirt = Save $11
    • Save at Home: Extra 25% off All Sale
    • Member Exclusive Sale: Save up to 40%
    • We want to save you some money
    • NEW SHORTS! Plus, save 20% when you spend $75 💛
  • Urgency subject lines we love:

    • Hurry, buy now during the Fall Savings Event.
    • Hurry… Your Exclusive Ends Midnight ⏳
    • Hurry – Your $5 in rewards expires soon!
    • your special treat ends soon…
    • Ending soon: 50% off entire site!
    • It’s your last chance.
    • Last Chance // 40% off Sandals Ends Tonight
    • 💋Don’t miss our BIGGEST deal yet!
    • Don’t Miss This Spring Deal! ⌛
    • Don’t miss out on these AMAZING offers ✨
    • Your favorites are almost sold out
    • Almost Sold Out! 🚨
    • Low stock alert ✨
    • Don’t miss out! 💙 Low Stock Alert

Common subject line mistakes to avoid

Email marketing professionals all have the same goal when writing subject lines: to win that all-important open. But on their road to achieving this mission, many make critical errors that sabotage their campaigns. Scroll through your inbox—chances are you’ll see some perfectly legitimate senders who are guilty of these subject line mistakes:

Overly long subject lines

As mentioned above, space is at a premium when writing email subject lines—so it’s best to keep things short and to the point. Long subject lines will get cut off by the receiving mailbox provider and make it difficult for them to know what the email is about. To avoid truncation, we recommend keeping your subject lines between 35-40 characters.

Vague subject lines

Subject lines should pique subscribers’ interests by giving them a taste of what’s inside. Avoid vague or generic subject lines like “Hello” or “Important information,” and use more descriptive subject lines that clearly convey the purpose of the email.

Subject lines with excessive punctuation

A golden rule of good email copywriting is to write the way you talk. Even seasoned email marketing pros make the mistake of cramming subject lines with excessive exclamation points, symbols, or ALL CAPS. While marketers hope it will drum up excitement, it can easily have the opposite effect. Senders run the risk of annoying their subscribers so much they’ll unsubscribe or manually mark emails as spam. Plus, this can look spammy to mailbox providers—earning your email a one-way ticket to the spam/junk folder.

Misleading subject lines

Don’t resort to cheap tricks or misleading pronouncements to persuade subscribers to open your emails. Using a subject line that is misleading or inaccurate is a sure-fire way to annoy the recipient and damage your relationship. While some marketing spin is expected, don’t promise anything in a subject line that you’re not prepared to deliver in the email.

Find better subject line ideas

For even more tips on subject line testing, check out this blog post. 

If you’re looking for more subject line ideas, sign up for a free MailCharts account today.  

With a free subscription, you’re able to use our advanced search options to search by subject line length, subject line content, and emoji usage. The app also gives you insight into the subject lines your competitors are using.  

Editorial image by M. Maggs from Pixabay

Post tags   Email Marketing Strategy