| Apr 6, 2016 | | 8 min read

11 Email Subject Line Best Practices to Boost Open Rates


The subject line is the first thing a recipient looks at when they check their email. In fact, 35% of recipients open email based on the subject line alone (Convince & Convert). Of all the factors that affect your open rates, this is where you should be spending the majority of your time and energy.

When it comes to email marketing, the number one thing all of us marketers care about is conversions. But if your recipients don’t open your email, you sure as hell ain't getting any click-throughs and conversions.

For every marketing email you compose, you need to strive to build a clear, concise and intriguing subject line that avoids buzzwords. The following best practices will help you get there.

1. Experiment with different styles 

To start, you have to put on your thinking cap and get creative. Skim through the content of your email and use your intuition to determine the key message you’re communicating. Use this as the basis of your subject line.

Now think about the styles of subject lines that make YOU want to open an email. There are a variety of different types you can use to get the attention of your target audience.

Email Subject lines with lists

Lists are an effective way to catch your recipients’ eyes. Numbers stand out from words visually, plus people are curious to discover what the list includes. If you’ve written blog posts or hosted webinars, you’ve likely used this tactic before. When your email highlights a blog post or webinar that uses lists, showcase that list in your subject line.


Subject lines with questions

A question in your subject line inadvertently creates a call-to-action. Your recipients are more likely to open the email to get the answer, or simply gain a better understanding of why you’re asking. Questions can also cause your recipient to pause for a split-second to consider their own answer.

For Vendasta’s weekly newsletter, two of the top three open rates were from subject lines posed as questions. For example, our best email subject line was “Who's your best salesperson?”, a question we used to highlight the new salesperson leaderboard functionality we released that week. Coming from a personal email address (i.e. our VP of Sales George Leith), this question undoubtedly intrigued our recipients. “What could this email be about?” “Why is Vendasta’s VP of Sales asking me about my salespeople?” “Who is my best salesperson?”

Conversational subject lines

When sending from a personal email address, you give yourself a little more flexibility with subject lines. Conversational subject lines are written in a way that makes an email appear as if it’s a casual message delivered personally by the sender. This tactic is especially useful for sales campaigns, where the emails are sent by the salesperson assigned to your partners. For a Vendasta sales campaign, we used the subject line “Quick question,” a simple, casual and personal phrase. This subject line, combined with a familiar sender, garnered a 45.0% open rate (where the call-to-action was a simple reply to the email).

And more!

Your target audience is unique, so try different styles to discover what works best for them. You might consider trying these other unique subject line styles:

  • Reason why. Ex. “Why B2B marketers still struggle to convert leads”
  • How-to. Ex. “How to create urgency to fuel e-commerce sales”
  • Controversial: Ex. “3 reasons your drip campaigns suck”
  • Urgency: Ex. “It's the last day of your trial”
  • Mysterious: Ex. “The guru of gurus tells all…”

Recap: Determine your topic, try new styles every week and discover what styles are most successful for your target audience.

2. Use a unique subject line for every email

If you’re using the same subject line for every version of your newsletter, you might notice that your open rates begin to decrease over time. Here’s where I’d like to share a valuable email marketing secret: The #1 best practice for writing effective subject lines is… describing the subject of your email. Since you write unique content every week, your email subject line should always be unique and relevant. Use a different subject line for every email in your campaign, and ensure it describes your content.


3. Keep your email subject line concise.

The problem a lot of marketers have with writing effective subject lines is that they feel this sort of irresistible urge to highlight too much of their content directly within the subject. This is a problem because recipients already get bombarded with marketing emails every day, and many of those emails also contain 60+ characters in the subject line. When your recipients skim through their emails and take that split second to scan your subject line, you need to stand out.

MailChimp and Yesware found in their research that shorter subject lines do not result in greater open rates. And those findings are relevant, to an extent. For Vendasta’s weekly newsletter, we found that the rather lengthy 50-59 character range has actually been most effective, with a 24.91% open rate. But I wouldn’t recommend a subject line longer than 60 characters because most email clients will truncate the rest of your subject, and that will obviously take away from your message. For Vendasta, subject lines over 60 characters have landed us our worst average open rate—21.56%.

To ensure your subject line fits on all smartphone screens, you should try to keep your subject line under 40 characters. Again, anything more than that may be truncated, meaning you won’t get your entire message across. And when more than 50% of emails are opened on mobile devices, your subject line’s appearance on mobile matters, big time.

Keep in mind: Conciseness matters. When you convey the same message in fewer words, your subject line will be more compelling.

4. Personalize your subject lines

Personalized subject lines garner 26% higher unique open rates than non-personalized subject lines (Experian). This statistic truly depends on your industry, company and recipients. But generally speaking, when your recipients see their company name, city name, software usage details, etc., they recognize those details and feel that much closer to your message. Essentially, they feel like they’re getting some sort of special treatment.

At Vendasta, we used the subject line “A First Look at [Company_Name]'s Virtual Doorway” for another sales campaign. This personalized subject line (again, with a familiar sender—the assigned salesperson) achieved a 42.1% open rate (with a 24.1% CTOR).

Keep in mind: Industry best practice is to vary your subject lines between personalized and non-personalized to ensure you don’t come across as spammy, especially when you’re using the same piece of information to personalize your message.

5. Be strategic with buzzwords in subject lines

You must be cautious and strategic when choosing keywords for your subject line. Buzzwords can boost your open rates, hurt your open rates or simply land your email in everybody’s spam folder. Oh, and the results ultimately depend on the industry you do business in. Confusing right? Use Adestra’s Email Subject Line Keyword Checker to test your keywords against the buzzwords they’ve researched.

You’ll find that words like “free” or “trial” will boost open rates in certain industries. However, keep in mind, when you combine these words with other buzzwords, like “sale,” your email might get sent directly to spam folders. There are hundreds of these buzzwords that could redirect your blood, sweat and tears to every marketer’s worst fear: the spam folder. It’s impossible to be aware of every spam trigger, so use your discretion. If you’re really curious, do a Google search for “spam trigger words.”

If your email doesn’t automatically end up in the spam folder, your recipients might still see it as spam and mark it as such. Convince & Convert found that “69% of email recipients report email as spam based solely on the subject line.” So use your judgment—if it sounds spammy, it probably is.

6. Consider symbols/emojis in subject lines

Although some people see emojis in subject lines as a gimmick, others feel that these little graphics are a fun and effective way to stand out from other text-only subject lines. As a result, adding symbols to subject lines is a gutsy tactic with high risk/reward potential.

The trick is to use an emoji that is highly relevant to your message. For example, “6 hot sales tactics to try in 2016 ?”. Irrelevant emojis in your email subject lines will not boost your open rates—in fact, they’ll probably hurt your rates.

It’s actually surprisingly easy to use symbols. Simply copy one from a free website like FSymbols.com and then paste it into your subject line.

Most symbols are supported in most email clients, including Gmail, Outlook 2007/2010/2013, Apple Mail, Android Mail and Yahoo! Mail. If a symbol is not supported, the recipient will see a ☐ character instead, so make sure you’re using a tool like Litmus to ensure your subject lines appear properly within these email clients.

7. Use square brackets strategically

Square brackets can help your recipients differentiate between what’s a [Webinar], an [eBook] or a [Video]. For example, earlier this month, the LinkedIn Marketing Solutions blog sent me an email with the subject line “Introducing The Sophisticated Marketer’s Guide to Content Marketing [eBook].” They also sent me “Top B2B Marketers Reveal How to Optimize Your LinkedIn Marketing Efforts [Video].” This is the only way square brackets should be used.

8. Draft 5-10 unique email subject lines

Just like when you’re brainstorming the title of a blog, eBook or white paper, writing multiple subject lines gives you the opportunity to compare and contrast what appears to be the most intriguing content.

As you write each subject line, challenge yourself to make the next one clearer and more concise.

Once you’ve written 5-10 subject lines, ask a coworker (or two) to pick the subject line they find most effective.

9. Use A/B testing often

No matter how many tips and tricks you read about subject lines, your target market is unique and will react to your subject lines as such. You need to find out what works for them.

A/B testing means comparing two versions of something to see which one performs better. Use this technique for your subject lines. Popular email marketing platforms like MailChimp and Pardot allow you to essentially split your email into two versions, and then deliver each version to a percentage of your recipient list as a test. The version with the highest open rate is then sent to the rest of your recipient list.

10. Monitor your email analytics religiously

Keep an eye on your email analytics to see how your subject lines affect open rates. By doing so, you’ll gain a better understanding of what types of subject lines get the highest open rates for your target market. Keep in mind that there are several other factors that affect open rates, such as the sender, day and time. Monitor everything.

Back in the day, the subject line of Vendasta’s weekly sales webinar invite read “Vendasta Weekly Webinar Invite.” One day, the open rate dropped to an all-time low of 16.63%. Boy, those were dark days. But until we started monitoring our email analytics and testing new subject lines, we had no clue. Since varying our subject lines every week, our open rates for the webinar invite have ranged from 23.01% to 29.35%—that’s more than 300 extra opens per email.

11. Remember: Your open rates will never be perfect

As much as you and I strive to improve our open rates until we reach the impossible—100%—there’s one thing holding us back: how open rates are measured.

Open rates require that an email is in HTML format and contains a tracking image (most marketing programs embed an invisible 1x1 pixel image within the content). If you’re not sending in HTML format, it cannot be tracked. That’s usually not an issue. But more commonly, your recipients’ email clients may block images upon the initial load of the email. Although they’ve opened the email, you will never know.

That’s where the click-through rate—a super reliable email analytics metric—comes in handy. Stay tuned for one of my upcoming email marketing blog post on CTRs. Until then, test out these email subject lines best practices for yourself. Leave a comment below to tell me what email subject line tactics you found particularly successful.

About the Author

Blair is a former Product Marketing Specialist at Vendasta and a connoisseur of all things digital marketing.

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