The Psychology of Subject Lines: How to Trigger Opens Without Clickbait

How to Write Subject Lines That Increase Open Rates

The first 50 characters of your email decide everything. They determine if your campaign drives revenue or gets buried under a pile of unopened promos. That tiny strip of text is where psychology meets persuasion. 

We’ve all opened an email that promised the world and delivered nothing. That’s the problem with clickbait, and customers always remember. It makes perfect sense though, clickbait is easy to write, instantly grabs attention, and temporarily boosts open rates. However, you can easily improve your subject lines with a few simple tactics. 

What's Wrong With Clickbait?

Clickbait is only a problem when it is misleading. Don’t conflate genuine scarcity or FOMO with clickbait. If you are actually running out of stock, you should advertise that. If your promotion will only last for 24 hours, advertise that as well. It becomes a problem when you advertise the same 24-hour promotion multiple days in a row. Customers will lose trust in your brand, and unsubscribe rates will shoot up. 

Subject lines with generic statements or questions are also bad for your brand’s reputation. Examples include:

“Could this be interesting to you?” , “You need to see this!” , “Super Sale, Today Only, Act Now!!!”

Understand Your Customer

Fantastic subject lines are easy to write. You should spark curiosity while also making sure your message is relevant to the customer. The first step to writing a good subject line is to fully understand who you are writing to. Great subject lines don’t come from copy hacks; they come from knowing your customer better than anyone else. At Avalon, we conduct customer research for every brand we work with before sending a single email. 

Conducting thorough customer research is key. Once you know your customer’s primary interests, needs, and goals, all you need to do is reference those in your subject line. Easy right? 

Let's take a long-distance runner. The runner could be primarily interested in healthy living, supplements, and the outdoors. If we were to write a subject line for a pair of running shoes, we would need to tie any of those interests to the running shoes and write a subject line.

Here's an example:

“Exclusive: The Running Shoes For People Who Chase Sunlight, Not Screens.”

This subject line does two things right. First, it directly relates to the customer, their interests, and values. Secondly, it transparently sells the product. We don’t need to rely on clickbait to grab their attention, we just need to show them that we understand them. 

Here is another example:

“[Customer Name,] You'll regret wearing any other shoe!”

This subject line sparks interest, and even has a personalized touch. However, it makes a vague claim that would be almost impossible to prove or deliver. This subject line is generic and not written for any specific person. I mean, everybody wears shoes. 

Rule of thumb: If the subject line applies to everybody, don’t send it. If it applies to a specific person, values, and interests, it's worth testing. 

Utilizing Data

Consumers today expect brands to know what they are interested in. With the advancements in AI, we can intelligently predict customer spending habits. The best brands already do this. Amazon, for instance, doesn’t send the same email twice. Every subject line is generated from behavioral data, and that level of personalization is now possible for you too.

Most ESPs track on-site customer data and allow you to use that data to send personalized, relevant emails. 

You can write personalized subject lines based on behavior data. For example, if a customer recently browsed jackets, you can see that data and automatically send “Best jackets for Fall 2025.” This re-engages the customer with something relevant, instead of a generic promotion that they may never open. 

Hypothetically, if the customer viewed jackets for kids, we can predict that they are a parent and place them in a “parents” segment. Now, instead of writing a subject line for jackets, we will write a subject line for parents shopping for a jacket for their child. 

Here’s an example:

“Parents are loving this best-selling kids jacket”

This is how you write personalized, relevant emails without resorting to clickbait.

The Psychology Behind Subject Lines

Your subject lines must trigger an emotion. Emotions act as highlighters for the brain. When something makes us feel something, it gets recorded in our long-term memory.
Formula for emotions:

Emotional Response = Relevance X Intensity 

This is why it is extremely important to relate to, and understand your customer. Sending them a relevant email is half the battle of triggering an emotion. Intensity can be increased by offering discounts, evoking FOMO, and even generating hype.
Let’s enhance the running shoes example:

“25% OFF: The Running Shoes For People Who Chase Sunlight, Not Screens”

Simply changing “exclusive” to “25% OFF” can increase the intensity factor and trigger a stronger emotional response, leading to an opened email. Intensity doesn’t always mean discounts; it could mean urgency, exclusivity, or social proof. Understanding your customer is the best way to know what makes them act! 

Emotions don’t have to be strong to be effective. You don’t have to make your customer jump out of their seat in excitement, you just need to nudge them subconsciously. The split-section impressions of trust, ease, and excitement can make a huge difference in your customer’s journey and their decision to open your email. 

Emojis

You either love them or hate them. Opinions on emojis are mixed. Many people believe that they’re great at grabbing attention, but data often finds no increase in open rates by adding emojis. (Reference)   

So what's the verdict? Use them sparingly, only if your target customer uses them. A coffee brand that sells to teenagers and young adults would see better results with emojis than a health and wellness brand tailored to middle-aged adults. Emojis don’t replace psychology. They're seasoning and useful only when they fit the flavor of your audience.

Wrap Up

The psychology of subject lines isn’t about tricking people, it’s about connecting with them. Every open starts with empathy, not exaggeration. So before your next send, ask: Does this line reflect what my customer actually values?
Chasing the best clickbait subject line is a race to the bottom; these are the messages that get buried in your customer’s inbox. When you target their problems and interests effectively, the customer is far more likely to give your email a chance.   

At Avalon, that’s how we write emails that get opened, and remembered.