Using AI to Optimize Subject Lines and Increase Open Rates

If email campaigns are not already a central focus of your marketing efforts, they should be.

On average, for every single U.S. dollar invested in email marketing, the return on investment is $36. The ROI was even higher in the retail, ecommerce, and consumer goods sector, with $45 earned per $1.00 spent.

Subject lines can determine whether or not a customer will open your email and – in turn – buy from you. But crafting a subject line that stands out in the inbox has traditionally required time, creativity, and a strong understanding of audience behavior. Often, this involves rounds of brainstorming, testing, and tweaking — a process that, while valuable, can strain resources. This is where AI can come in handy.

With the ability to instantly analyze data patterns, audience preferences, and engagement history, AI-driven subject line generators, like Knak’s, enable marketers to skip the trial and error. Instead, they can focus on results and produce subject lines that align with campaign goals and audience preferences.

How AI-Powered subject line generators benefit your email campaigns

AI-powered subject line generators revolutionize how you create impactful email campaigns, offering immediate, diverse options tailored to your goals and audience. By simplifying the process and providing actionable insights, these tools let you craft subject lines that stand out and resonate—all while saving valuable time.

Efficiency and Speed in Campaign Development

Crafting the perfect subject line often leads to multiple brainstorming sessions and rounds of revisions. AI simplifies this process by offering immediate, diverse options tailored to the campaign's goals and audience. With an AI-powered subject line generator, teams can bypass the lengthy ideation phase and access ready-to-use options that are both creative and effective.

Seamless Integration in a No-Code Environment

For many marketing teams, agility and accessibility are key. Built-in subject line generators like Knak’s are embedded directly into the email creation process, providing an intuitive, no-code solution. This seamless integration empowers all team members — regardless of technical expertise — to benefit from AI-driven insights.

How to use AI subject line generators to increase your email open rates

As AI becomes an integral part of crafting email subject lines, it’s essential to use it effectively to achieve the best results. Here are some best practices to help ensure that AI-generated subject lines not only capture attention but also drive engagement and align with your campaign goals.

Prioritize brevity

To maximize readability and engagement across devices, aim for short, descriptive subject lines, ideally under nine words. Clear, concise messages quickly communicate value and are more likely to grab attention in a crowded inbox. When guiding AI, prioritize brevity to ensure messages stay impactful on both desktop and mobile screens.

Personalization will double your open rates

A recent study found emails without personalization in the subject lines have an average open rate of 16.67%, while emails with personalized subject lines have an average open rate of 35.69%.

Personalized subject lines can boost engagement by making each email feel tailored to the recipient. Leveraging AI, subject lines can include specific details, like the recipient’s name or interests, to create a stronger connection. For example, “John, new features just for you” speaks directly to the individual, increasing the likelihood of a click. This personalization aligns with modern consumer expectations for relevance and authenticity in brand communications.

Include a value proposition

Effective subject lines communicate what the recipient will gain from opening the email. Direct AI to generate lines that highlight clear value propositions, like “Double your leads in two weeks” or “Get more engagement with these tips.” By articulating what’s in it for the reader, AI-generated subject lines help drive both opens and conversions.

Incorporate verbs to inspire action

Strong, action-oriented verbs inspire recipients to take immediate action. By using language like “Discover,” “Shop,” or “Start,” AI-generated subject lines can create a sense of urgency. For instance, “Shop our new summer range today” uses compelling verbs to inspire action, helping drive engagement and creating a clear call to action within the subject line.

Avoid clickbait-y, misleading content

Building long-term trust is essential to keeping your email recipients engaged. Ensure your AI-generated subject lines are always accurate, free of clickbait tactics, and avoid spam-like language. Authenticity in subject lines leads to greater customer loyalty and open rates over time, as recipients learn to trust the content within your campaigns.

Create curiosity while staying clear

Intrigue can drive engagement, but clarity should never be compromised. Encourage AI to craft subject lines that spark curiosity without being vague or misleading. For example, “What’s new in your favorite product line?” provides enough intrigue to interest the reader, while also being informative.

A/B test for optimization

A/B testing subject lines helps identify which options resonate most, allowing teams to guide AI with refined prompts based on real-world results. This continuous improvement loop ensures that your subject line generator delivers maximum value.

Using AI for More Than Just Subject Lines

Beyond generating subject lines, integrated AI can support various aspects of email creation to enhance your overall campaign effectiveness.

Don’t forget about the preview text

One study found that 24% of subscribers decide whether or not to open an email after reading the preview text, and that email preheaders can lead to a 7% higher email open rate.

AI can automatically generate compelling preview text that complements the subject line, providing a seamless reading experience from inbox to message. This alignment between subject line and preheader ensures message continuity, allowing the preview text to add context or further entice the reader without duplicating or diverging from the subject’s core message.

Use AI to streamline your campaigns

Most integrated AI tools – including Knak’s – go beyond subject lines, generating both subject and preview text within a single, unified platform. This not only simplifies workflows but also enhances efficiency for marketing teams, who can rely on the AI to craft cohesive messaging elements without switching tools. By keeping the entire process within the same integrated tool, teams save time and reduce the friction often associated with disjointed, multi-tool workflows, enabling faster campaign execution without sacrificing quality.

Maintain consistent messaging across all campaigns

Consistency is key to building a strong, cohesive brand experience. Integrated AI tools help unify messaging elements, allowing marketers to maintain consistency across every component of the email—from subject lines and preheader text to the body copy and calls to action. By aligning messaging within one platform, you can minimize the risk of disjointed or mismatched elements, fostering a unified and professional appearance that enhances brand credibility and reader engagement.

Why integrated AI is better than generic solutions

For email marketing teams looking to harness the full potential of AI for their campaigns, an integrated solution offers clear advantages over generic tools.

Shortcomings of standalone AI

While generic AI tools like GPT have their uses, they often lack the targeted capabilities that dedicated email marketing AI can provide. Standalone models may offer suggestions or content, but they don’t have access to campaign-specific insights or continuous optimization based on past performance. With integrated AI, each email campaign draws upon data-driven information specific to your business and campaign.

Create a purposeful foundation

AI is most impactful when it’s purpose-built. Integrated AI tools are designed specifically for email marketing, enhancing campaign success by understanding the nuances of the field. Unlike generic AI, which may lack focus, integrated AI insights evolve with each campaign, creating a continuous improvement loop that makes future campaigns even more effective.

Empower your marketers at every skill level

Integrated, no-code AI tools allow marketers of all backgrounds to benefit from advanced technology without technical expertise. With it, you can remove the barriers of complexity, enabling anyone on the marketing team to generate high-quality subject lines, preview text, and more. This not only accelerates campaign development but ensures that every team member can contribute to effective, data-driven campaigns.

Use Knak AI to streamline your next campaign

Knak’s integrated AI features make it easy for marketers to handle every stage of their email campaigns, without leaving the Knack platform.

• Subject Line Generator: Quickly craft compelling subject lines that drive engagement, with options to customize tone and style to match your brand.
• AI-Powered Translations: Translate emails and landing pages into over 75 languages instantly, ensuring consistent messaging across global audiences.
• Preview and Preheader Text Generation: Complements subject lines by creating seamless and engaging preview text, boosting open rates and reader interest.
• Alt Text Generation: Automate descriptive alt text for images to improve accessibility and enhance user experience.
• Localized Content Management: Easily manage and edit localized email versions in one place, ensuring cultural relevance and streamlined campaign workflows.

Watch a demo of Knak to see how we're utilizing AI in our platform.