Communicate and Persuade: 6 Email Subject Line Best Practices

12/19/2019 Haley Windahl

Communicate and Persuade: 6 Email Subject Line Best Practices

In today’s digital-first environment, it’s easy to forget that the first impression many consumers have of a brand (on most days) is the subject line of an email.

Email marketing has become a staple of modern consumer communication. One that’s becoming harder and harder to get opened, let alone get noticed.

What can help you break through the clutter? Effective subject lines.

The starting line: industry benchmarks

Before you begin revamping your subject line strategy, you should always compare your performance to any available benchmarks. 

Lagging behind industry averages in open rates? Then prioritizing a new approach to subject lines is a smart business decision.

For email metrics to have any meaning, you need to make sure you are looking at benchmarks within your industry. Here are a few free resources I recommend to help you establish your benchmarks:

In this article, I'll will walk you through what to consider when creating a subject line that your consumers will appreciate. In order to do that, we will explore the two main goals of a subject line: communicating your message and persuading the reader.

Communicating the message

Almost 60% of in-house marketers have said that their top priority for email marketing is creating shorter subject lines that still include the “key message in the first 30 characters” [source].

Do you try to tell a new acquaintance everything about yourself in the first 30 seconds? No. So why try to do it in a subject line? 

General best practices

Subject lines are a form of short copy that requires a deeper understanding of your target customer and a knack for translating a larger message into a few words designed to strike the right chord. While they may seem obvious, the following sample of best practices should never be forgotten:

  1. Put important information first.
  2. Be customer-focused. Remember: What the company thinks is important is not always what the customer thinks is important.
  3. Calls to action often perform well (e.g., Watch, Shop, Download).
  4. Create a sense of urgency when relevant. Do it too often and there’s a good chance you’ll ruin it for those emails that really are urgent and time-sensitive.
  5. Don’t try to deceive your customers for more opens. Successive emails will suffer as a result.

No matter what information is included in your email, it is always best for your subject line to be short (45-50 characters max), honest, and straightforward.

Spam triggers

The main benefit of being honest in your subject lines is that you avoid increasingly vigilant spam triggers. A simple internet query — for example "subject line spam triggers" — will provide you lists with the most popular (as well as lesser-known) trigger words these filters are looking for. 

Always check your proposed subject line against the words and phrases in these lists — or study these lists beforehand so you don’t include them in the first place.

Gmail’s Promotions tab

Gmail’s “Promotions” tab. Many email marketers loathe it. We say embrace it. Google introduced this inbox feature as a way to separate marketing or retail messages from standard communications. 

Many of our clients have viewed this change as a negative and are trying to find ways to avoid the “promotions” distinction. Gmail is going to put you there based on several aspects, including the number of emails hitting their servers (volume of your send), content, domain reputation, and even the size of the email.

Our opinion? Brands should focus on embracing the existence of the Promotions tab for two reasons: 

  1. Google isn't going to remove it. 
  2. It can actually become a great resource for subscribers who don't interact with your message immediately but do want to come back to it at a later date.

This means your strategy should focus less on how to escape the Promotions tab and more about how to stand out and make the most of it. 

Persuading the reader

An estimated 40% of consumers say that the overall subject line is what persuades them to open an email. Another 41% of consumers say they will open an email if the subject line offers a discount of some kind

Those are powerful numbers. 

Regardless of your writing ability, simply including a discount in your subject line can multiply your open rate by many times. However, you can’t include a discount in every email. You need to stay in business, after all. 

Other, more persuasive tactics in subject lines include:

  • Asking questions. Simply put, questions can engage the reader’s brain. 
  • Creating a sense of urgency when relevant. If there is a time-limit on whatever you need your customers to read or do, let them know.
  • Using interesting or impressive numbers or lists. People love statistics and lists.
  • Being timely and relevant by referencing current events and news (when it makes sense). Don’t just jump on the bandwagon, but if your company is involved in something big, or has something valuable to add to the conversation, then tell your audience.


According to a February 2019 GoodFirms survey, email marketers rank email personalization of emails slightly higher than subject line optimization. So personalizing the subject line can be an effective strategy. A few natural examples of personalization include:

First name: Haley, take 25% off your entire order today!
Interests: Haley, stock up on Muscle Milk Whey Protein to increase your gains!
Birthdays/Anniversaries: Happy Birthday Haley! Enjoy double rewards points on us!
Transaction history: Haley, it’s time to reorder your C4 Pre-workout!
Urgency: Haley, 25% Off Ends Today!
Location: Haley, stop into our Westlake store today for BOGO vitamins!


Subject lines are the most popular tests conducted by email marketers for a couple of reasons.  1) They are extremely effective. 2) They are not terribly difficult to execute. Here are some variables to consider changing when testing your own subject lines:

  • Personalization 
  • Symbols/Emoji use
  • Length (short vs. long)
  • Questions vs. statements
  • Capitalization
  • Digits vs. words
  • With or without branding
  • Positive vs. negative tone 

Conclusion: Make your subject lines communicate and persuade

Econsultancy's "Email Marketing Industry Census 2018" revealed, 49% of email marketers worldwide believe artificial intelligence (AI) could help them improve their email subject lines.  I consider that proof cutting through the clutter has become serious business — and harder than ever before. 

To improve your open rates, I encourage you to use the tools and resources at your disposal (like this post on avoiding email fatigue).

Consumers are getting smarter and much more discerning in what they open and what they trash. Smart marketers will continue to strive to find a balance between persuasion and clear communication.


Haley Windahl is an Assistant Account Manager at RRD with proven experience in managing email campaigns through a variety of ESPs, including SFMC, Adobe, and Responsys.

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