Can AI write better subject lines than a real person? Perhaps. Brands like JOANN have seen their email open rates increase by 10%, all thanks to AI.
Unless you’re an expert email marketer, it can be difficult to come up with great subject lines every time. This is especially true if you’re sending personalized emails multiple times per week.
Also, you may need to write multiple subject lines and run split testing to find the best one. This is time consuming!
This post will explore how AI works with the email subject line and why you should take inspiration from AI when writing email subject lines. You will also learn about some of the best AI email subject line generators.
How AI works with email subject lines
Many AI technologies are still in their infancy. They look good on paper but have not reached their potential. That said, there are other AI content generators that have grown rapidly to become game-changers.
It is this second group that is driving the AI explosion we are seeing today. In particular, two technologies have driven AI progress:
- Natural Language Processing (NLP)
- Natural Language Generation (NLG)
NLP is when a machine “reads” text. It converts that text into code that the machine system can interpret. NLG is when a machine uses that code to generate its own words.
These technologies are found in AI-powered marketing tools like AcroLinux, which uses NLP to assess your content and recommend improvements. Another major use case enabled by NLP and NLG is, you guessed it, writing email subject lines.
Apart from saving time, another benefit of AI tools is that developers use large amounts of data to train them on email engagement.
These data are based on email best practices, enabling AI tools to create bias-free subject lines that can lead to higher open rates.
As Perry Malm says, “When humans make choices, they incorporate their own experiences, thoughts, and beliefs.” This can create bias and force us to select subject lines that may not be the best.
But AI is free from bias, and it is trained using clean data. “AI output is based on pattern matching, which is invisible to the human eye and devoid of cognitive biases that lead to poor decisions,” Parry says.
Now, let’s look at some of the best AI tools for generating email subject lines.
4 AI tools to generate email subject lines
I tried most of the AI email subject line generators and barely found ones that made the cut. Some output did not follow best practices, as subject lines were long.
Below are four of what I consider to be the best AI email subject line generators in 2023.
1. HubSpot AI Email Writer
Get started with HubSpot AI Email Writer
HubSpot’s AI Email Writer enables you to automate email copywriting for sales outreach, email marketing, and more. It’s versatile, allowing you to tailor email copy for different audience segments by prompting them to write in different tones.
You can choose from email marketing templates and use slash and highlight commands to get emails tailored to your needs.
Additionally, HubSpot’s AI Email Writer easily integrates with HubSpot CRM to automatically log conversations and contacts.
Price determination: Free.
best for: venture companies
Persado is an AI platform that allows users to personalize communications at scale and inspire audiences to engage and act.
The brand has $66 million in funding and offers AI email subject line writing in addition to automated social media and language generation for enterprise marketing.
One reviewer, who is a senior email marketing and analytics expert, says:
“We’ve seen strong growth in open rates with Persado, and we’ve been able to learn more about our audience. Persado categorizes subject lines by sentiment, providing insight on the language that motivates your audience, and taking the pain out of writing high volumes of subject lines.
Price determination: Pricing available upon request.
best for: Medium-sized and enterprise companies
Phrase uses AI to create email subject lines, write email copy, and generate email CTAs. You feed it email data, and it analyzes the data to figure out what works.
It generates optimized subject lines that can perform better than human-made ones. And it uses what it learns from your emails to stay consistent with your brand.
In one case study, Freese helped Virgin Holidays increase its open rates by 2%. It might not seem like much, but it was worth millions of new revenues. The tool has also streamlined a process that previously took weeks – today, it takes seconds.
Price determination: Pricing for Freese starts at $500 per month, billed annually. To access enterprise features, you will need to contact Freese’s sales team for a quote.
best for: Individuals and companies looking for free AI tools
There’s a good chance you’ve heard of ChatGPT. ChatGPT is a free AI tool that provides the best responses based on the quality of your signals.
When using ChatGPT, it’s a good idea not to just ask it to create a subject line. Include the email you want to send and ask to create subject lines for that email.
Here are two examples of prompts you can use to get subject lines:
- “Create 10 subject lines based on the emails below. Each subject line should include a probable percentage of its likelihood of being opened. Here is the email…”
- “Write 10 email subject lines for the emails below. Each subject line should end with a question and contain an emoji that indicates curiosity.
- “Write 10 email subject lines for the emails below. Each subject line must be seven words or less and end with a question mark.
Pro Tip: To get the most out of ChatGPT, you need to be very specific with your signals.
Leveraging AI Email Subject Line Generators
One beautiful element of AI is that it operates with less human involvement. At HubSpot, we see the value in this.
That’s why we’re developing HubSpot AI – a content assistant and ChatSpot for generating email subject lines and even creating emails from scratch.
Get started with HubSpot’s Content Assistant
Hopefully tools like this will ensure that we’re not tied to our creative ideas.
Look, humans aren’t that good at writing and split-testing emails, creating social media content, writing headlines, and choosing the best subject lines based on data.
Hey, we get it wrong sometimes. Here, AI is better equipped than us for the task. It specializes in analyzing large amounts of data and extracting insights from that data.
For example, Phrase regularly uses 100,000+ emails as a dataset. this is too much!
So, often, AI can write email subject lines better (and faster) than humans. This is good news because it improves your marketing.
Instead of drowning in data and having little time or budget to maximize performance, marketers can use AI to automate and enhance their processes. They both improve performance and free you up to perform higher-value tasks.
In many cases, this is a win-win scenario. Marketers get better results and do what benefits their brand the most (which is the most interesting thing anyway).
This is why marketers need to experiment with AI. Understand the tools out there and what they can do for you.
AI has a “first-mover advantage” in marketing right now. Let’s say I start using a tool like Freesy to write my email subject lines.
I improve my performance almost immediately. I reinvest hours each week into creating better campaigns in every area of my marketing.
And, I collect more and more data on which subject lines work best, which improves performance even more. This is a virtuous cycle. A flywheel that spins faster the longer you stick to it.
In other words, the benefits of using AI correctly grow over time. Competitors with a big lead are hard to catch. Someday, this may change.
But right now, marketing AI is skyrocketing. Brands that use it have more profits than brands that don’t use it.
No matter what type of marketing you do, one thing is clear: you need to explore the possibilities of AI. These tools can help you write the best email title and improve your copy.