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10 Best Practices for Email Subject Lines Your Customers Will Click

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Email marketing is a proven way to turn prospects into customers and one-time buyers into recurring customers. 

Engaging subject lines help make that happen by standing out in your customers' inboxes. But inboxes are crowded, and the average consumer sends and receives 118 emails per day. You need compelling subject lines to stand out from the crowd.

So what makes a subject line compelling?’s Kristi Meyer, Senior Manager of Customer Strategy/Lifecycle Marketing points to 10 best practices for subject lines that break through the noise.

Use Personalization 

Using customers’ first names is a simple, effective way to personalize your emails. You can pull other data for personalized messages, like companies’ website addresses and other customer file information. 

Just make sure the data you’re using for personalization is accurate. Personalization is great, but it doesn’t work without good data. “At the end of the day, it does come down to the data and how accurate it is,” says Kristi. Bad data can make for embarrassing personalization mistakes. 

Keep Subject Lines Short 

Kristi likes short subject lines because “it makes them more impactful.” She’s not alone. This is backed up by several email studies, including an interesting survey of 1,000 top experts in marketing that found subject lines between 21 and 60 characters seem to work best. 

Make Sure the Subject Line Matches the Content of Your Email

Clickbait doesn’t just happen on Facebook. It can happen in inboxes too. So don’t write subject lines that misrepresent the email message they announce. 

Don’t be deceptive in any other way, either. One example of this is adding “RE:” to the front of any subject line. “RE:” makes it look like the sender is replying to an email you sent them, but it’s a spoof – they’ve just added that “RE:” to make it look like that. 

Tricks like this not only get caught up in spam filters, they also make your readers feel like they’ve been duped after they open the message. It erodes trust in your brand.

“Split-Test” Subject Lines

Run ongoing tests of your email subject lines to see what works best for your customer base. Kristi typically does this by splitting an email list in half and sending one version of a subject line to the first group, then a different subject line to the second group. Then she compares the response rates between the two messages. 

Open and click-through rates aren’t all that matter in the analysis. What you ultimately want are actual conversions. While you should take notice top-of-funnel metrics like open rates, focus more on conversions. 

By tracking tests like this, you’ll get a sense of what a particular audience will respond to. That knowledge can help you design better email campaigns. 

Here’s an example of an email subject line split-test. This company sent out two versions of this email, and because I’ve signed up twice to get their emails, I just happened to get each version:

Send Test Emails Before You Schedule a Campaign

Email marketers have an ongoing challenge to make their messages look good on the dozens of different devices people read emails on. Subject lines are particularly challenging to write because some email clients will truncate subject lines after only a few words. 

The best way to manage this problem of different devices is to test them extensively. Test your emails before you mail them out to your subscribers. Most email service providers offer built-in tools that let you send test emails to different email accounts so you can view them on different devices. Or you can use a third-party tool like Litmus to see how your emails will look on multiple devices and email clients. 

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Put the Key Part of Your Message at the Front of the Subject Line 

If you really want to squeeze more into a subject line, work with how the words may be truncated. That may mean adding a dash at the end of your subject line to squeeze more information in, or using a “|” symbol to break out different topics or sections of the email, like this:

Another reason to try to get the main benefit of your subject line in early is that you’ll have a better chance of catching subscribers’ attention as they scroll through their inbox. When people have dozens of emails to review and delete, they may only read the first few words of a subject line. If you don't capture interest within the first few words, they may not come back for a second read. 

Use Emojis – If They Fit With Your Brand

Everyone’s seen emojis in their inbox – those little symbols that some email marketers use in email subject lines. But do they work? Kristi says emoji can lift email open rates, “but I do think they need to be reflective of your brand.” If your brand is in a serious field, such as legal or finance, you might want to be careful with how you use emojis. 

Econsultancy would agree. They did a study that found emojis do lift response rates for emails, but they also learned this: “Emojis are language amplifiers. An emoji, in itself, won’t make or break a subject line. The data proves this. But, they can be an additive – or subtractive – linguistic feature.”

Here’s an email subject line where the emojis are part of the message. It’s from a B2B brand that has a professional but somewhat playful voice:

Make the Most of Preheaders 

Preheaders are the greyed out text that appears below (on mobile) or after (on desktop) the email subject line. Preheaders often get overlooked by marketers, but they can be an excellent way to complement the subject line. One of Kristi’s favorite subject line formulas is to ask a question in the subject line and then answer that question in the preheader. 

Use Brackets as an Attention-Grabber

Brackets can be especially good for communicating a particular content format or to designate a particular type of email message. Because they can be used almost like labels, brackets can help you communicate more information in a very tight space – which is exactly what we want to do to keep subject lines short. 

A subject line format like “[Webinar] How to Write a Landing Page” or “[Ebook] How to Grow Your Email List” often works well. Here's an example:

Think Like Your Customers to Write a Great Subject Line

If you’re not a copywriter, writing a subject line might seem a little daunting. You’re actually right to feel some pressure: Anywhere between 35% and 47% of surveyed consumers say they open email messages solely based on the subject line. If that wasn’t enough to give you performance anxiety, 69% of emails are marked as spam based on the subject line

While that is a bit intimidating, don’t worry. Anyone can write a strong subject line if they’ve got the right mindset. 

"The most effective subject lines are those which capture what the email is about," says Kristi. "Ask yourself these questions: What are the most important nuggets that I’m trying to get out of that email? Is there a product or service that we want our customers to notice? Are we having a sale on domain names, such as 20% off? Ultimately, decide on the most succinct way of saying that topic in the subject line so it would make me want to open up that email."

Pay close attention to the reporting from previous email campaigns. By looking at that data, you’ll see trends over time and uncover things like asking questions for a particular audience often works really well. Questions can create a sense of urgency. When paired with personalization, particularly first name personalization, they are especially effective. 

Images: Shutterstock