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How to Write the Perfect Subject Line [Infographic]

I’m going to go ahead and admit that there’s really no such thing as the perfect subject line—or, if there is, it must be hiding with Bigfoot and the Loch Ness Monster. After running subject lines through A/B split tests every month in our own newsletter, we’ve yet to find the secret formula (or even a statistically significant result). Alas, we’re not out to mislead you but rather guide you toward perfection. Here’s our tips on how to write the perfect subject line.

Writing subject lines is hard. Most of us leave it until the last minute. It seems like the entire world is riding on your email’s subject line (What will get more opens? More clicks? More conversions? Oy!) Compounding this pressure is questionable lists of words to avoid (lest you hit a spam filter), “best practices” and generally conflicting advice coming from every corner of the internet.

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One day you might read an article telling you to write really short subject lines, and the next day your boss sends a whitepaper showing that long subject lines perform better. A single source might even reverse a previously held position with a subsequent article.

What’s an email marketer to do?

  • Keep your subject line straightforward
  • Avoid using promotional phrases or, well, things that look (or sound) spammy
  • Know your audience. What will interest them?

Check out more copywriting tips for subject lines in our Email Copywriting series.

Take the Melting Pot Approach

The infographic below gathers some of the most common myths, advice and trends we’ve heard about recently. Think of it as food for thought (and not a definitive guide) for the next time you’re writing a subject line and get stumped. Test a few tactics and see what works for you. Come back and let us know what works (and what doesn’t) in the comments. Check out the additional resources at the very bottom of this post: there are many different (and occasionally conflicting) opinions represented there. We’ll be testing, too!

It may seem like the art of crafting a subject line is complex and intimidating, but it’s actually pretty straightforward. Subject lines should, simply put, describe the subject of your email. Yes, really—that’s it!

Click on the graphic for an enlarged view. The entire text of the graphic is also available below.

How to Write the Perfect Subject Line

The Opening Line

Crafting The Subject Line That Gets Your Email Read

With email as a primary method of communication, the average working professional receives over 100 messages a day. How can you make your email stand out from the sea of emails in your subscribers’ inboxes? That’s where the subject line comes in—use it to get your subscribers’ attention and get your emails opened!

Subject-Line Mythbusting

It’s an old wives’ tale that certain practices will get you immediately marked as spam. Spam filters can be triggered for a variety of reasons, but specific words alone rarely are the culprit.

  1. Using all caps
  2. The ultimate four-letter word: free
  3. Exclamation points

How content filtering actually works

Spam filters assign points to “spam” words in the subject line and body of an email. If the points exceed a certain threshold, then the email is considered spam. However, using any one (or two or three) of these words won’t automatically mean a trip to the junk folder. While content filtering plays a part in spam scores, your sender reputation and engagement metrics are much more important.

What Works?

A recent MailChimp study analyzed the open rates for more than 200 million emails to determine which types of subject lines trigger recipient opening. Here are some of the strategies that worked, as well as others that fell flat.

Leveraging localization

Collecting (and using) geolocation information can improve open rates by being personal and relevant.

[Example]: Nautica in Rutland Opens Soon!

Ask away

Subject lines framed as questions perform better. Consider your audience’s needs, interests, or the types of questions your content might answer.

[Example]: What’s your dream adventure?

Keep it short and sweet

Email marketing company MailerMailer found longer subject lines had lower open and click rates than those that were shorter. Try to say it all in 50 characters or less.

[Too long: 98 characters] Final reminder for complimentary entry to attend the West Freelands BCI Cluster Conference 2006

[Get to the point! 24 characters] Your April Website Stats

Emails with 28–39 characters in the subject line had the highest click rates.

Subject line lengths and their corresponding open and click rates:

  • 4–15 characters: 15.2% open; 3.1% click
  • 16–27 characters: 11.6% open; 3.8% click
  • 28–39 characters: 12.2% open; 4% click
  • 40–50 characters: 11.9% open; 2.8% click
  • 51+ characters: 10.4% open; 1.8% click

Proceed At Your Own Risk

The following strategies might drive quick opens but aren’t long term-solutions for improving your marketing.

Symbols and Special Characters: Hearts, airplanes and coffee cups might get your email opened, but the jury’s out on their effect on clicks.

[Example]: ♥ it? Get it at 40% off!

Using “Re:” and “Fwd:” to imply that your message is from a trusted colleague or friend borders on deception and might damage subscriber trust.

[Example]: FW: Get Connected at our B2B Networking Mixer

Fear of being scammed has left many consumers skeptical of emails with pleas for assistance or requests for help.

Using numbers can help quantify your message, but constant sales and promotions can lead to subscriber fatigue and general loss of interest.

[Example]: SALE ends soon — Up to 50% off!

Including the recipient’s first or last name does not significantly improve open rates.

[Example]: Matthew, SNAZZY SHOES wants you back

In a July 2012 study, MailerMailer saw significantly lower CTR and open rates for personalized subject lines comparedto non-personalized ones.


When writing the subject line for your next email, consider the following techniques.

  1. Useful and ultra-specific: Make sure it is relevant, valuable, and the message is clear to your subscribers.
  2. Identify yourself: Is it crystal clear to your subscribers who your email is from? Mention your most recognizable brand product in your subject line, or prefix your subject lines with a consistent identifier:

Example: [BCPL Happenings] Nationally Renowned Author to Speak

  1. Be visually different: In order to make your email stand out, you can try to make your subject line stand out visually: Consider using brackets, variations on capitalization, phone numbers, quotes, etc.
  2. Use timely topics and urgency: Hit home on a point that is top of mind for your subscribers, such as something in the news or a popular topic. Urgency works for real deadlines, but can be overdone.
  3. Call to Action: People respond well when you ask (or tell) them to do something. What do you want your recipients to do?
  4. Test it out: Test which subject lines resonate best with your audience, so you can repeat success.

In a nutshell: what are the dos and don’ts of subject lines?

Do set your subscribers’ expectations and clearly state what’s inside the email. Don’t write your subject lines like advertisements. The folks at MailChimp say it perfectly – “When it comes to email marketing, the best subject lines tell what’s inside, and the worst subject lines sell what’s inside.”

Always check your subject lines with Litmus Checklist

Check off “eye-catching subject line” on your final pre-send checklist using Litmus Checklist. With Checklist, you can preview your email in 50+ apps and devices, validate that your links, images, and tracking work properly, test your email’s load time, and more–all before pressing send.

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