Your Guide to Writing the World’s Best Email Subject Lines

Here’s how to write can’t-wait-to-open subject lines, and avoid going straight to the trash folder.

Before it hit shelves, F. Scott Fitzgerald’s The Great Gatsby was almost titled The High-Bouncing Lover.

Doesn’t have the same ring to it, huh?

Writing your email subject line is a lot like choosing a book title: You have to get it right, or people may never open it — no matter how fantastic the content is inside.

In fact, 47% of email recipients admit to opening email based on the subject line alone.

47% of email recipients open email based on the subject line alone

One of the most common questions we hear is: “what do I write in the subject line of an email?” Many people wonder how to write perfect email subject lines.

While there’s no single formula to create the best subject lines for email marketing, the following battle-tested guidelines will get you pretty close to perfect. They can help you make your messages even more appealing to your subscribers.

Apply them to your email subject lines, and you could be the next Fitzgerald of the inbox.

(Looking for an email service provider that lands you in the inbox — and not the spam folder? Get AWeber Free today! We have 20 years of industry-leading deliverability!)

Tips for Writing Email Subject Lines

Email subject line tip #1: character length

How long should your email subject line be?

No one can agree.

Litmus recommends around 50 characters. Yet Lifecycle Marketing says emails with subject line up to 20 characters have the highest average open rate, unique click rate, and click-to-open rate. An analysis from Retention Science found that subject lines with 6 to 10 words results in the highest open rates. And Return Path advises using 61 to 70 characters.

So in reality . . . it depends. (Sorry, I know that’s no one’s favorite answer.) Every industry — and audience — is different.

But here are some important things to keep in mind when you’re testing various subject line lengths — no matter what industry you’re in:

Chart showing 67% of email opens are from a mobile device
  • Is your preheader text cut off? If so, will your subject line still make sense without it?
  • Are there words you can cut to be more concise or clear?
  • Is your message clear and direct?

Email subject line tip #2: use emojis

In a busy inbox, an emoji (or a special character, like a carat ^, hashtag #, or tilde ~) can stand out. In fact, emojis may increase your open rates by 29%.

  • AWeber Blog: “Why you need a hook 🎣”

At AWeber, we use emojis in our messages every so often to pack a punch, or to shorten a subject line. For instance, we might use a 💡 instead of writing out the word lightbulb to keep the entire subject line visible on mobile devices.

Some emojis look very different from one Internet Service Provider (ISP) to the next. So don’t forget to test your emails in various ISPs like Gmail, Hotmail, and Yahoo!, too. Here are 3 Ways to Test Your Emails Before Hitting ‘Send.’

If you choose to use emojis, beware: Emoji usage in marketing messages is on the rise. So there’s a chance your emoji may not stand out as much as you’d like. Our advice: Test them with your readers. See if your readers act positively to emojis through increased open rates.

What’s next?

There’s no single formula for writing the most successful email subject lines. But if you mix-and-match the subject line rules and tips above, you’ll be able to optimize your open rates over time and come up with a formula that works extremely well with your audience.

To find out which types of subject lines your audience likes best, run an A/B split test. Leverage what works, then test again. The type of subject line that works for your audience today might not be as effective six months from now. Watch your open rates closely so you can adapt and improve.

Want to try out a new subject line today? Log in to your AWeber account to get started. Don’t have an AWeber account yet? Get AWeber Free today!

I’d love to hear from you, what was one of your best eblast subject lines that worked?

Post written by contributing writer Marijana Kay and Sean Tinney


  1. Daisy

    7/11/2018 6:08 pm

    I often have trouble with the subject. very nice tips, going to practice them soon, THUMBS UP!

  2. Jill Fanslau

    8/20/2018 9:25 am

    Thanks, Daisy!! Let us know how it goes!

  3. Rafal Alitojc

    7/12/2018 4:04 am

    Thanks for this great and interesting article.
    I’m sure it will be helpful for many people 🙂

  4. Lee Smith

    7/12/2018 8:52 pm

    Thanks! I’m a newbie and I equate learning these skills to learning a foreign language. It takes a lot of repetition before it becomes second nature!

  5. Gill

    7/18/2018 12:22 pm

    Thank you so much for this, Marijana. Love the no-fluff advice!

    Re my Great Gatsby: I once reviewed 50 small business websites and wrote a post about their common mistakes . Some of those websites belonged to my subscribers. So, when promoting the post in my newsletter I used the email subject: “Good news: I reviewed your website!” The preview line said: “Bad news: It wasn’t the best”.

    I’ve never got such open and click-through rates again 😄

    Generally speaking, I noticed the more specific and relevant the subject is for your subscribers, the higher the engagement.

    Thanks again for such a great post. I’ll make sure to spread the word.


  6. Jill Fanslau

    8/20/2018 9:24 am

    Wow, Gill! That’s a fantastic idea. No wonder you got such great engagement. At AWeber, we’ve found that specificity does lead to higher open rates. It shows you know your audience, and you’re sending them value. You’re talking to the individual — not the crowd. Highly relevant subject lines paired with segmentation is a winning duo. Keep up the awesome work.

  7. Ella Monte

    11/3/2020 10:21 am

    Thanks for sharing your thoughts. Keep posting insightful insights article and look forward to reading more from you.