The Email Subject Line is Everything

Chances are, you email your customer base. You've built a list, maybe you push out a newsletter or a promo every now and then. Maybe those emails have done alright.

Or maybe they haven't.

You can have the greatest, most relevant content in the world inside your email, but unless your recipients open it, they are never going to see it.

This is why the subject line matters so much. Let's break it down...


Limited Real Estate

We often don't think about email subject lines in the context of length, or more specifically, character count. But there are limits that are determined by how your recipients receive email. Using the standard Mail app on an iPhone 8, in portrait mode (aka how you normally hold a phone), email subject lines are limited to 48 characters before they are truncated with an ellipsis. Rotate the device 90 degrees and you'll see far more characters. On your computer, either in a browser or a desktop app, even more characters will show because you have more real estate.

The point is twofold: 

  1. Device, browser and app all impact the number of subject line characters (including spaces!) that will show. 
  2. To be safe, aim to get your message across in 45 or less.

What to Write?

Far too often email subject lines fall flat. They fail to attract attention and they fail to compel recipients to open. That means they're dead on arrival. In today's endlessly noisy world, you can't just rely on the content of your subject line. You have to get scientific. Sumo, a suite of digital marketing tools, has a blog post in which they run the numbers on 87 different subject lines types. Yes, 87. Not all will apply to your business, but some of our favorites include:

  • The How To ("How to reduce your payroll costs" or "How to enjoy wine like a pro")
  • The Avoid ("Avoid these 3 tax mistakes" or "Avoid hiring a lousy PR agency")
  • The Three Points ("Hoagies, Wings, Beer" or "Shoes, Scarves, and Shades")
  • The You're Not Doing ("The 'it' fall style you don't know about yet" or "Why aren't you doing this new workout?")
  • The Question ("Are you going to miss this sale?" or "Will you be there?")

ABT (Always Be Testing)

The best email marketers are always testing to optimize for the future. You always want to learn something from an email campaign. In terms of the subject line, test different types using some of the styles shared in the Sumo article. Most email marketing systems allow you to conduct A/B tests in which a small percentage of your audience gets one subject line and an equally sized percentage gets another. The remaining subscribers get the one that was opened the most.

You can also test sending at different times of day, on weekends, in batches, by subscriber demographics ... the email marketing world is your oyster. Just be sure that whatever you test is teaching you something.


Increasingly, brands have been inserting emojis into their subject lines. This is fine (and even effective), but context is everything. If you're a seafood restaurant, throwing some fish emojis into your email subject line makes a lot of sense. Fish emojis in an accounting firm's email subject line? Probably not a fit (unless their niche is the seafood industry). Equally important is understanding your audience and the devices they consume your emails on. Most email marketing systems will tell you what device and what email system your subscribers use. An emoji might show fine in Gmail but look all wonky in Outlook. Use emojis to achieve something. Don't use them because they're cute.