How to Write a Great Email Subject Line

No matter what someone tells you, email marketing is not dead. According to research done by Copyblogger, people spend 5.6 hours a day checking their email. Plus, email remains 40% more effective at converting leads than social media.

Email marketing is an art, and it all starts with your subject line. You may not know the key to a good subject line, but you know it when you see it. So, let’s go beyond that and break down the elements to dominating your open rate with the best tips on how to write a great email subject line.

Top Tips for Email Marketing Subject Lines

A/B Testing

First thing on how to write a great email subject line, do not write just one subject line per email. Come up with at least two and run an A/B test to see which garners the most opens. Run your test to 25% of your customer list for one hour and then send the winner to the remainder of your list. Make sure to choose open rate at the measure of success.

When deciding different subject lines to test, think about testing different elements of content to your list. Add the element, for example an emoji or personalization tag, to one of the subject lines and then leave it out of the other. This will allow you to see which types of subject line elements your customer list receives the best.

Don’t be afraid to test more than two subject lines against one another. Now don’t get crazy and test 10, but two to four is a safe range that will allow for the best result and tangible data.

Pro-Tip: Most email marketing platforms will allow you to choose the timeframe in which they will automatically send the winning subject line to the remainder of your list. Automating your tests makes it easier to test more frequently.


Which subject line would you be more likely to open?

“Share the love on Valentine’s Day”


“❤️ Share the love on Valentine’s Day ❤️”

Clearly, you would choose the subject line with the emoji. When you scan your email, especially on mobile, it’s all in black and white. So, when an emoji is used, our eyes are immediately drawn to the color and make us more likely to engage with that email over another.

Not sure which emoji to use? According to Constant Contact, the top 10 emoji’s their users are including in their subject lines are as follows:

  • Red Heart ❤️
  • Beaming Face with Smiling Eyes 😁
  • Registered Trademark ®
  • Smiling Face with Heart Eyes 😍
  • Eyes 👀
  • Green Heart 💚
  • Thumbs Up 👍
  • Raising Hands 🙌
  • Backhand Index Pointing Right 👉
  • Purple Heart 💜


Let’s be honest, all of us are a little vain. When we see our name on something, it immediately makes us feel valued and important. Same thing goes for personalization in subject lines. If you have up to date data, it is always a good idea to use it to capture the attention of your customer base.

Here are a few personalization subject line examples:

  1. Hi [First Name]
  2. Exclusive Offer for [First Name] Only >>
  3. We miss you. You last purchase date was [Date]

Just be careful, you want to make sure that the subject line is still organic and makes sense if you do not have the needed personalization tag information.

Pro-Tip: Segment your list based on having customer data and not. For example, if you want to use the subject line “Hi [First Name],” send that subject line to all of those whose name you have and write a different subject line like “Checking in to say hello,” to all of those who you don’t have a first name for.


“Offer expires at midnight”

“Last Chance Deals >>”

“Today Only!”

You need to give people a reason to open your email. While you might think that just putting the offer information in your subject line is enough (and sometimes it is), often times you need to add some urgent language to sweeten the deal.

Don’t worry, you can always extend the offer to capture those who did not take advantage of the first offer. Deadlines are arbitrary, except for when you want someone to convert.


Capitalization can be a little subjective. There can be something to be said for writing your subject line in all caps, just don’t abuse it. If all of your subject lines are in caps, your customer base might feel like you are yelling at them. Make sure to use this tip in moderation.

On the other hand, having your subject line in all lowercase can have just as powerful an impact. By writing your subject line in all lower case, it will stand out among all of the shouting going on in someone’s inbox.

Pro-Tip: Try and A/B test of an all caps versus an all lower case. While some customer lists might react well to one, your list might react well to the other. You will never know until you test it and see which comes out on top.


According to Touchstone, adding an exclamation point to your subject line can increase your open rate by up to 20% (!!!). Like capitalization, punctuation is something tend to get a little crazy with. While it can be impactful, make sure not to get too carried away.

Pro-Tip: Don’t just stick to the standard punctuation marks like the period, question mark and exclamation point. It is good to step outside of the box and try some different things. Some punctuation to try would be brackets ([  ]) and the greater-than sign (>).

Don’t forget preview text

Too often people forget all about the preview text when learning how to write a great email subject line. While the preview text is technically not a part of the email subject line, it is equally important. For those of you who do not know, the preview text is the content that appears directly to the right of the subject line. It is generally between 35 and 90 characters long, depending on if you’re reading your email on mobile or desk top.

Take this opportunity to:

  • Introduce your content
  • Share an offer or promotion
  • Continue your subject line

How to Write a Great Email Subject Line Final Thoughts

Learning how to write a great email subject line should not be daunting. The moral of the story is to test all of the tips we mentioned to see how your customer list will react the best. Whatever gets our list to open, is what you should do. But if you see the open rate start to trickle down, it’s time to switch it up and refer back to our list of tips for email marketing subject lines.