AI Email Subject Line Generators: How to Use AI to Boost Opens

AI Email Subject Line Generators: How to Use AI to Boost Opens

The quest to capture your audience's attention begins long before they dive into the content of your email—it starts at the subject line. With inboxes cluttered with hundreds of daily messages, it's the compelling, well-crafted subject line that often makes the difference between an open and an ignore.

However, creating top-notch email subject lines (day after day) is easier said than done. Need help?

Fortunately, there are AI email subject line generators.

Email subject line generators leverage the power of AI to craft titles for your emails. Just enter a prompt to get dozens of options. You won’t always find a generated option perfectly polished and ready to send, but the generator will return plenty of ideas and starting points—and that’s better than staring at a blank subject line field.

Why email subject line generators matter

Just as the contents of a gift don’t leave an impression until the recipient unwraps it, emails have no impact unless opened. And subject lines are crucial to influence what happens once the message arrives in an inbox.

Consider these statistics:
  • 64% of people base their decision to open emails solely on the subject line
  • 69% of people will report emails as spam after reading only the subject line
  • 50% more emails get opened with a personalized subject line
  • 66% of businesses don’t personalize subject lines
Unfortunately, many marketers treat their subject lines as an afterthought. They might labor over the body copy and images, A/B test the call to action, and debate the contents of the footer. But then, they hastily write a subject line the moment before the email goes out. 

Some organizations even require email teams to write all subject lines just before sending, even with no prior knowledge about the project.

If you treat your subject lines as afterthoughts, your recipients will likely view your emails in a similar light.

How AI subject line generators work

While a human creates subject lines based on their experiences, preferences, and hunches, a subject line creator has access to vast stores of data. You don’t have time to analyze millions of emails sent over the past year, but AI does. By reviewing metrics and user data, email subject line generator AI will make strategic, fact-based suggestions.

But what about your brand’s unique voice? Your recipients expect a certain tone and personality from your communications, and you don’t want to compromise that with more subject line options.

Fortunately, AI delivers the best of both worlds. 

Most subject line generators have fields for email body copy and your preferred tone, ensuring the writing is in line with your brand voice. Additionally, there are tools that analyze recipient responses and then generate content to align with their preferences. So your emails will maintain brand integrity and resonate with your audience.

In addition to the subject line’s tone, most tools also include fields to input crucial message details. Examples include:
  • The name of your organization
  • The type of email you send
  • The sender’s name
  • The recipient’s name
  • The chosen keywords
Once you’ve entered these details, you’ll have a list of potential subject lines within seconds. Will each one be perfect? Of course not. But you’ll have many options.

Review the list and choose the two best lines for A/B testing. It’s crucial to note that constantly testing and refining is necessary in this era of AI-powered tools. The more data you gather, the more effective you’ll be. And it all empowers you to provide the best customer experience possible.

The best tools for AI email subject lines

Let’s check out some of the top options available. Some of these email subject line generators are free, while others require a subscription. There are basic platforms with only a few input fields, and ones that utilize sophisticated technology to write your entire email and help create other marketing content.

1. Mailmunch

This email engagement platform offers a basic subject line generator for email. Just input details such as the name of your organization, the objective of your communication, and the tone you want to use, and you’ll get a batch of recommendations.

Get started with the 30-day free trial. If you want to continue with Mailmunch, plans start at $13.99 a month.


Now fueled by ChatGPT-3, the latest version of is a major upgrade from the earlier product. For example, its natural language processing (NLP) interprets user motivations and delivers compelling messages better than ever.

While offers a robust suite of email products, starting at $79 a month, you can get free, unlimited access to the email subject line tool without an account. is one of the best free subject line generators on the market.

3. Anyword

As with, this email marketing subject line generator has a wide range of offerings. Anyword creates email copy, blogs, product descriptions, and more. While some subject line helpers only provide a list of ideas, Anyword scores the suggestions to help you identify the strongest options. And because it has input fields to specify your audience and the text of your email, you get tailored results.

Following the free seven-day trial, plans start at $39 a month.

4. Scalenut

This popular AI email subject line generator has varied subject line options, including short and long character counts and even the occasional emoji. Scalenut also has the added benefit of an editor that helps you proof all email content.

With a seven-day free trial, you can test out Scalenut before signing up for a monthly plan. If you decide to stick with this tool, paid plans start at $20 a month.


If just starting out with email subject line tools, might be a good option. With its user-friendly interface and advanced NLP, it can create the content for your entire email, making the subject line, preheader text, headlines, and body copy more cohesive. offers a free plan with limited monthly output or more robust plans that start around $15 a month.

6. Yet Another Mail Merge

If you need batches of five subject lines at a time and appreciate simplicity, consider this catchy email subject line generator. Just paste the email body copy into the field, select your preferred tone, and you’ll get suggestions within seconds.

Like most free email subject line generators, YAMM’s functionality has limitations. But it’s user friendly and meets the needs of many marketers.


Here’s another free subject line generator worth a look. offers a full range of AI writing tools, including its popular subject line assistant. Start by entering your product or brand name, add in the email body copy, then select the tone you’d like to embrace in the subject line.

You can use the free plan with as long as you want. The cheapest paid plan starts at $36 a month and allows five users and unlimited usage.

Refine your AI-generated email subject lines with Twilio SendGrid

Each of these AI email subject line generators offers unique benefits, so don’t be afraid to experiment with them to find the ideal match. Email is a crucial marketing channel, so your time investment will certainly pay off.

And if you need help, remember that Twilio SendGrid email experts are standing by to provide insights and answer questions. We can help you build templates, automate your campaigns, and analyze the data to refine your strategies.

Get started by creating your free SendGrid account today.

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