4 Hacks You Should Know Before You Craft Your Next Email Subject Line Since email open rates are so dependent on great subject lines, consider these tips to get your audience clicking instead of deleting.

By Zach Bulygo

This story originally appeared on KISSmetrics

Every day people are flooded with emails they must decide to open or ignore. Research by Epsilon shows that email open rates are hovering around 25%. Luckily for marketers, there is a way to improve that rate.

Since many people base their decision (about whether to open an email) on the subject line, this means you can optimize it, through testing and iteration, and attain an open rate that is far above average.

In this post, I will share four hacks you can use in your email marketing. Most of these hacks are backed by research, although results vary by industry. (Of course, there is no perfect subject line. The most important thing you can do is experiment and find what converts your mailing list.) These are hacks that I hope you'll apply in your future email tests:

1. Write Your Email Subject Lines for Mobile Devices

These days many people are accessing their email from their phones. Research from Litmus tells us that almost half of us are viewing email on mobile devices, with the rest either using a desktop program or accessing through webmail. The majority of email clients are Apple devices:

  1. iPhone —— 26%
  2. Outlook —– 14%
  3. iPad ——— 12%
  4. Gmail ——- 11%
  5. Apple Mail — 8%

So when crafting your subject line, it's important to think about how it will appear on all devices.

this image shows the differences between inboxes of iOS, Blackberry, and Android

iPhone cuts off subject lines at around 35 characters:

image showing iOS cutting off subject lines

Android wraps to the next line:

image showing how Android wraps the subject line

You may want to just assume that your email subject line will be viewed on a mobile device. Write the whole email for mobile. There are no excuses left if you are not optimizing for mobile.

2. Keep Your Email Subject Lines Short

Research by MailerMailer has found that shorter subject lines have higher open rates and click rates. Work at keeping your subject lines under 50 characters.

Separate research done by Retention Science found that subject lines with 6-10 words had the highest open rate, and subject lines with words in the 0-5 range had the second highest open rate.

The Obama campaign was very effective at raising money through email. A few of their top converting emails began with these subject lines:


I will be outspent

Some scary numbers

If you believe in what we're doing…

Last call: Join Michelle and me

Would love to meet you


The most popular Obama

Michelle time

Thankful every day

The one thing the polls got right…

All of these subject lines are under 50 characters and their emails are among those that brought in the most donations. (The "from" address in a few of these emails was "Barack Obama," which probably also helped improve open rates.)

I'd encourage you to run open rate and click rate tests on different subject line lengths.

3. Personalize Your Email Subject Lines

Personalized emails fall under the umbrella of emails that are unique to the recipients. This can include an email that mentions the user's name in the subject line or an email triggered by the actions the user performed on your site. Personalized emails cut out broad email blasts and instead are automated and unique to each recipient.

They have been found to be pretty effective, too.

Research by Retention Science found subject lines that included the recipient's first name had a 16% higher open rate.

More research performed by MailChimp showed that personalizing the first name and last name had the strongest impact on open rates.

Some marketers choose to send personalized emails that aren't necessarily triggered by any previous actions the user took on the site. A few examples:

Udemy uses my first name, but does not mention any specific classes I may be interested in:

image showing Udemy using a first name in an email subject line

Flipboard includes my first and last names as well as some topics:

image showing Flipboard using first and last name in an email subject line

This triggered email from Amazon uses a book title as the subject line. This book title is based on my previous browsing history:

image showing Amazon using a product name in an email subject line. This subject line is based on previous browsing history

This triggered email is based on an episode I watched using Amazon Instant Video. It's further personalized by including my first name:

image showing an email from Amazon using first name and the Breaking Bad episode Ozymandias in the subject line

Here are a few ideas on using triggered and personalized emails, categorized by business type:

SaaS Businesses:Problem: If a user hasn't logged in

A "Why haven't you logged in?" email is too bland and may turn some people off. This subject line gets to the root of the matter by asking them for feedback on the product:

How can we make the product better for you?

SaaS Businesses: – If a user hasn't set up or used a feature:

This is a good subject line if a user hasn't set up or used a specific feature in your app:

Can we help you set up {event}?

SaaS Businesses: – If a user sets up a feature but doesn't return again:

You can use this email if you have a user who set up a feature but didn't return to the feature for weeks. For KISSmetrics we may use this for someone who has set up a funnel but hasn't checked on it for 5 weeks. A product like Evernote might use this email subject line if they have a user who installed their "web clipper" add-on but didn't use it:

Check your results for {enter funnel report}

How can we make {enter feature name} better for you?

Check out how {enter feature name} is {performing, working, etc.}

E-commerce Businesses: – When a customer leaves a product in their shopping cart:

I'd wait a few days to a few weeks before sending this. Experiment with this and avoid sending it every single time a customer has left something in their shopping cart:

{First Name} – You still have {enter product name} in your shopping cart

E-commerce Businesses: – Running a sale on products:

Let's say you run an auto parts store and are having a sale this weekend for 35% off all oil filters. You can send emails to those customers who have purchased an oil filter from you in the past:

Save 35% on {enter oil filter product name they bought} this weekend!

E-commerce Businesses: – When a customer buys one product:

You can use suggestive selling to help you increase average order value. Using the same auto parts store as an example, let's say you had a group of customers who bought an oil filter but did not buy any motor oil. You can try sending these triggered emails a few days after their purchase (you could also mention it while they are in the shopping cart):

Buy {enter motor oil name} for {enter price per quart} per quart

Free shipping when you buy 6 quarts of {enter motor oil name}

4. Include Multiple Topics in Your Email Subject Lines

Traditionally email subject lines are only one topic. For instance, you probably get lots of emails like this:

Hurry! Sale Ends Tonight at Midnight!

25 Health Tips

Why You Need a New Phone

New Product Feature Announcement

These have only one message. If you're interested, you'll open the email. If not, you'll ignore it. So how can marketers improve the odds of getting their email opened? The best method is to use multiple topics in a single subject line. Here are a few examples:

Big Think gives subscribers two topics they could be interested in: living forever and improving brain function:

Subject line says How to Live Forever 12 steps and Improve Brain Function through meditation

LivingSocial mentions four separate product categories in this subject line. I may not be interested in jewelry, makeup, or magazines, but have a curiosity about healthy products. Therefore, I will open the email and see what the "Healthy Products Subscription" offering is all about. I may even go on to purchase the subscription. There wouldn't be any chance of this happening if LivingSocial used only "Sterling Jewelry"as the subject line.

subject line says healthy products subscription, sterling jewelry, mineral makeup, magazines and more

The Brain Pickings weekly email newsletter lists a couple of topics that can be found in the email:

email subject line says An illustrated love letter to life's meanwhile moments, George Lucas on the meaning of...

The advantage of this type of subject line is that they can have a much broader appeal. The marketers are casting a wider net by using multiple topics that will appeal to more people.

Obviously, this method of crafting subject lines conflicts with the 50-character limit discussed above in hack #2. My recommendation is to at least test this method and see if you get a higher open rate.

Some Final Thoughts

There is no such thing as the perfect subject line. As a marketer, you need to test your subject lines and see which ones get the most opens. (Now, clearly, getting people to open your email is only one part. After that you need to get them to click or tap on something in the email.) But you've won half the battle if you can get them to open the email.

I hope this blog post has helped give you some ideas for optimizing the most important part of an email.

Zach Bulygo is a blogger for KISSmetrics

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