Never judge a book by its cover. It’s great advice, but when it comes to emails, not many people follow it.

• When it comes to writing email copy, it's not hard to see why so much focus is spent on subject lines. Chances are that your subscribers receive many permission–based emails every single day. If your subject line isn't compelling, not only will it not get opened, but there's a chance that it won't even be seen. Joanna Wiebe shares her tips for creating captivating subject lines that get opened.
• Use the same email content, and write two different subject lines for both the groups. Then compare open and click-through rates to see which subject line performed best. One subject line could be more generic and the second could be more engaging. See which approach works best for your audience and pattern your future subject lines after that.

When writing email subject lines, the first thing everyone wants to do is stand out. Of course you have a desire to make sure your message is opened, but you don’t want to go overboard and be obnoxious, and you’d be surprised how often this happens.

An email’s equivalent of a cover is its subject line. It’s the first thing people see and for a third of people, the determining factor in whether they even open the email.

Two thirds of people also mark emails as spam based solely on subject lines.

So no matter how great your email is, if you don’t have a great subject line it’ll never reach its full potential.

But how do you come up with subject lines that work? What separates a good one from a bad one?

Well in this post we’ll take you through all the various things you need to take into consideration and elements to add and avoid.

Follow this advice, and you’ll realize much better email open rates in no time.

Email Subject Line Character Limits

When coming up with subject lines, you only have so much space before email clients start cutting off your message.

If you let your subject lines get too long, there’s also a decent chance subscribers will miss the most important parts altogether.

Subject line length also strongly correlates with open rates. The fewer the number of characters, the higher email open rates are.

A Litmus study found that having between 4 and 15 characters achieves the highest open rates. Whereas having over 50 characters results in the worst number of opens.

So having shorter subject lines is key to increasing your open rates.

If you’re looking for a hard character limit to ensure nothing is cut off, unfortunately the answer varies by email client. Keep in mind however that mobile devices will usually be much more aggressive.

For example, the iPhone Mail app, one of the most popular email clients in the world, tends to cut subject lines off around 45 characters.

So while 15 characters is a good number to aim for, sometimes this isn’t enough space to get your message across adequately. In these cases, remaining under 45 characters should still display your full message.

Subject Line Best Practices

Subject lines exist to inform your subscribers of the content of the email. This is something you should always keep in mind when writing them.

That said, they don’t need to be a dry clinical summary of your email. There’s plenty of scope to create engaging subject lines that people on your email list can’t help but click.

Achieving this requires a bit of creativity on your part, but by simply following the guidelines below you’ll well and truly be on your way.

Personalization

Hyper-targeting is crucial in digital marketing today.

Long gone are the days where you could simply blast out the same message to everyone. People expect personalized content.

Email marketing is no exception. Personalized emails result in over a 50% increase in customer satisfaction and receive 30% higher email open rates.

To ensure this success for your campaigns, it always helps to also personalize your subject line.

This isn’t just about including your email subscriber’s first name either. Rather also communicating that the entire email has been personalized to your subscriber.

Achieving this is obviously much easier when the content of the email is also personalized.

A good example are abandoned cart emails. These lead themselves well to subject lines like “{{name}}, don’t forget about {{product}}!” This grabs the subscriber’s attention and immediately lets them know the email is tailored to them.

So just as you should be sending targeted emails, remember to keep your subject lines personal too.

Clarity

Just to reiterate: the entire point of subject lines are to let people know what’s in the email.

Don’t forget about this or deliberately make your subject lines vague in the hope of people clicking through just to know what you’re on about.

More descriptive subject lines receive higher open rates. So if you’re not being clear, people will simply ignore your email altogether.

For email campaigns that you send on a regular basis, such as personalized product recommendations, you should also keep subject lines fresh.

SmartrMail makes this easy with the rotation tool that lets you use multiple different subject lines on a rotational basis.

Repeatedly sending the same subject line will only fatigue your email list and cause them to ignore your email.

Spark Subscribers’ Interest

In addition to being clear and letting people know what the email is about, you also want to hold a bit back to spark people’s curiosity.

While these might seem like competing demands, they’re not. Consider the following examples:

• Our Newest Ebook
• 10 Most Common Tax Time Mistakes
• Behind the Scenes at our Factory

These subject lines are descriptive while still being clickable.

Just like how emails filled with personalized content make personalized subject lines much easier, creating interesting content helps with enticing subject lines. So next time you want to send an email newsletter, make sure your content marketing game is on par.

CTAs

Calls-to-actions are powerful.

Including one in the body of your email can increase click through rates by 371% and your conversion rate by up to 1,617%. So why not include a CTA in your subject line as well?

Granted you’re working with a very limited number of characters, but if you can fit one in, it’s worth doing. If it doesn’t make sense though, or adding one will make your subject line far too long, then don’t force one in.

Time Sensitivity

Whether it’s email opens or sales, time sensitive offers are a great way to boost your conversion rate.

Including such an offer in your subject line can result in 22% higher open rates. Even just including the word “tomorrow” is able to increase open rates by 10%.

The email below demonstrates this tactic well.

Letting the recipient know that there’s only three hours left until the offer expires forces them to act.

Unless they want to miss out on the offer, they need to open the email as soon as they see it. This prevents them from intending to read the email later but only to forget about it entirely.

Time sensitivity isn’t the only way to achieve this.

You can also take advantage of people’s FOMO with scarcity. Doing so also compels people to open your email quickly. Subject line examples of this include:

• 7 seats left. Don’t miss out!
• Act Now: Limited Stock Remaining!
• The chance for tickets to NAMB19

Newsletter Subject Line Examples

Now that you know how to go about writing subject lines that work, it’s time for some inspiration.

The following examples are subject lines for email marketing campaigns that have worked well. Feel free to use them as inspiration for your own campaigns.

• “We Like Being Used” – The Muse
• “Deals That Make Us Proud (Unlike Our Nephew, Steve)” – Groupon
• “What The Eat In Prison” – Thrillist
• “Vanilla or Chocolate?” – Brooklinen
• “I didn’t see your name in the comments!?” – Kimra Luna
• “Learn a language with only 5 minutes per day” – Duolingo
• “Stop wasting money on ink” – HP
• “Since we can’t all win the lottery…” – Uber
• “Meet your new jeans” – Topshop
• “Products the celebs are wearing” – Sephora
• “Don’t Open This Email” – Manicube
• “You’re missing out on points.” – JetBlue
• “As worn in the World Tour” – Rapha
• “Stop wasting time on mindless work” – Evernote
• “Yes, this is a fundraising email” – Al Franken
• “Hey” – Barack Obama

That last subject line, “Hey”, is one of the best subject lines ever for open rates.

Obama’s relationship with supporters on this email list is likely quite different to the relationship you have with your subscribers. So while this may not work as well for you, it still demonstrates that short, simple subject lines tend to perform well.

How Not to Write Subject Lines for Email Marketing Campaigns

In addition to following the steps above, there are a few things you’re better off avoiding. This includes:

Spelling Mistakes

This is an obvious one, but always remember to use a spellchecker. While most good emails apps will have spellcheckers built into them, don’t rely on them having one.

Spellcheckers aren’t 100% perfect either. They don’t always pick up subtleties in grammar or regional variations. This can also lead to perfectly cromulent words and expressions being flagged as wrong.

Annoying Punctuation

Including excessive punctuation such as multiple exclamation and question marks will only make your emails appear spammy.

The same applies to writing your subject lines in all caps. While you might be able to get away with a word or two all capitalized, having every word in all caps is like shouting at your subscribers.

Too Many Emojis

Emojis can be a great way to make your subject lines stand out in people’s inboxes. That said, if you’re going to use them, limit it to just one or two.

Filling your subject line with too many emojis is like using excessive punctuation. If you manage to avoid the spam folder, sure you’ll stand out, but you’ll also annoy your subscribers.

If you want to use emojis, check out our emoji for email subject lines post.

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All of these points come down to one thing: don’t be annoying.

If you’re looking for more things to avoid, we’ve also written a more comprehensive guide on how not to write your subject line for ecommerce.

Looking for More Subject Line Examples?

6 Tips For Writing The Perfect Email Subject Line Example

If you’re looking for more inspiration, we also have blog posts full of great subject line examples for the following events:

We also have lists for certain types of emails, including:

There are only so subject line examples you can look at before you have to start writing on your ones though. Once you have some in mind, you can help ensure that you’re sending the best version with A/B testing. This helps ensure you get your emails opened as often as possible.

Best of luck with writing your subject lines!

6 Tips For Writing The Perfect Email Subject Lines