subject lines

8 Tips for Optimizing Email Subject Lines According to Zeta AI

Every email marketer knows the stress of trying to craft perfect subject lines. When the average person receives between 100-120 emails per day, it puts added pressure on the subject line to say, “Open me! This is the email you want to read right now!” 

There are countless articles out there from experts sharing their tips to improve this important piece of email copy. But what if we told you Zeta has the 8 best tips for subject line optimization, and we have the receipts to prove it? It’s true. With the new subject line optimization capability in the Zeta Marketing Platform, our AI provides live recommendations to improve subject lines based on real insights and activities across tens of thousands of email campaigns per month. Meaning they’re informed by data to determine what works. 

So here they are—the 8 best tips for optimizing email subject lines according to Zeta AI. 

Action words conveying urgency 

Customers appreciate subject lines that get right to the point. Beginning a subject line with words that convey urgency or a need for action—reminder, update, important, last chance—often inspire subscribers to take action. After all, nobody wants to be the one who misses out. 

Zeta AI says:  Subject lines beginning with action words generate a 64% lift in open rate versus ones without them. 

Make subject lines about you 

We all agree on the impact personalization has on maximizing marketing spend. Yet we sometimes forget the power of personalization when it comes to the subject line. Using words like “you” and “your” create a sense of exclusivity that resonates with customers—as long as that personal touch aligns with the content of the email, of course. 

Zeta AI says: Subject lines conveying personal or exclusive content generate a 63% lift in open rates versus generally addressed ones. 

Don’t bury the results 

If your subscribers are sports fans or news junkies, treat your subject line the same way a reporter would treat a headline. Don’t tease the outcome of a big game or an important election—lead with the results right in the subject line. Trust that your audience will want more. 

Zeta AI says: Subject lines communicating results generate a 60% lift in open rates.  

Show positivity and gratitude 

It’s simple, really. Customers like to be appreciated even with small gestures. Subject lines that say “thank you” and “congratulations” are proven to resonate with customers over time. 

Zeta AI says: Subject lines connoting appreciation generate a 42% lift in open rates.  

Keep subject lines short 

It’s not always easy, but creating copy that is crisp and gets right to the point using the fewest words possible always performs best.  And as more customers engage with their email on tablets, smartphones, and increasingly smaller devices, shortness is important for readability. 

Zeta AI says: Subject lines with 15 or more words result in a 21% open rate decline. Ones with 20 or more words result in a 33% open rate decline.  

Go ahead, use those emojis 

Is there a better way to keep your subject lines short than using emojis?  We think not. Emojis are proven to increase audience engagement and improve relatability as well as brand image. They should be used moderately however, and only when relevant to the content.  

Zeta AI says: Subject lines with emojis generate a 10% lift in open rates. 

Show them the numbers 

Research shows that numbers invoke curiosity and credibility, and Zeta AI tells us that research is consistent across all emails. From stats to listicles (hey look, you’re reading a listicle right now) customer attention is captured by ones with numbers. 

Zeta AI says: Subject lines with numbers generate a 2% lift in open rates. 

Ask them a question 

Asking a question can spark curiosity and motivate customers who want to know the answer. For example, “Do you know the top 8 tips to optimize subject lines?” would make a great one—asking a question and showing them the numbers for good measure.  

Zeta AI says: Copy that asks a question performs 4% better than ones that don’t. 

Bonus tip: Don’t forget about A/B testing your subject lines

We would be remiss if we didn’t take a moment to reinforce the importance of A/B testing. While the insights from Zeta AI are valuable to subject line optimization, it is true that A/B testing can provide different data points—for example, how do different generations respond to certain subject lines? What’s more effective, a 20% discount or free shipping?   

Are you a Zeta Marketing Platform user? If so, ask your account representative about our new subject line optimization feature. Curious but not a Zeta user? Check out the Spring Edition of our Launch Box eBook to learn more about subject line optimization and other innovations coming to the Zeta Marketing Platform or reach out to an expert today to learn more about how Zeta can help you with your email marketing efforts. 

Special thanks to Danny Portman, Manish Barnwall, Ekansh Verma, for assisting with  contributing insights from Zeta AI. 


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