Email marketing tool with AI that suggests subject lines

Klaviyo is a strong option: its AI suggests three subject lines from a description of your campaign, right in the campaign or flow editor. (help.klaviyo.com)

Other options:

• HubSpot — generates subject lines and preview text based on your email content. (knowledge.hubspot.com)
• Omnisend — offers AI subject-line suggestions in its campaign editor, including on the free plan. (omnisend.com)
• AWeber — includes an AI subject-line assistant in its email-writing tools. (aweber.com)

If you tell me whether this is for an online store, a newsletter, or a small business, I can narrow it down.

Here are the strongest options I found for email platforms with AI subject line suggestions. Most are full email marketing tools, and a few are standalone generators.

Full email platforms with built-in subject line AI

• Mailchimp: Its Intuit Assist feature works inside the editor and can suggest subject lines and write text blocks. Mailchimp starts from $13/mo and has a free plan for up to 250 contacts. It suits beginners.
• HubSpot Marketing Hub: Its AI Content Assistant generates email copy, subject lines, and CTAs inside the editor, and it can use CRM data to inform suggestions. This is the best choice if you already use HubSpot's CRM.
• GetResponse: It offers an AI writing assistant as well as an AI subject line generator. It's a good fit if you want to write, send, and track campaigns in one place.
• Brevo: It offers generative subject lines and predictive send-time, with a free tier. Pricing sources disagree on the entry price, so check the current page.
• Omnisend: It's aimed at ecommerce and includes a subject line and preheader generator. Choose it if you sell on Shopify or WooCommerce and want email plus SMS.
• ActiveCampaign: It's better for complex automations. Its AI can generate subject lines, copy, and images, but the full AI suite is priced differently across sources, with one citing $79/mo for the full set of features.
• Klaviyo: It is also listed among platforms with AI subject line generation, mainly for ecommerce teams. I didn't find enough detail in these results to recommend it specifically.

Standalone subject line generators (no email platform needed)

• Omnisend's free generator: Type in a few keywords about your campaign, pick a tone, and you'll get several options to use as is, edit, or A/B test.
• Jotform's generator: It's free and requires no account, and it creates suggestions from your email body or a description.
• Copy.ai or Jasper: These are general AI writing suites. Copy.ai offers a free subject line generator, with paid tools from $24 per month. Jasper is better for teams that need consistent brand voice.
• ChatGPT: It works well if you want flexibility and iteration. It can generate, group, critique, shorten, and rewrite options using detailed instructions.

My suggestion: If you already send email, use the AI built into your current platform, since it can tie suggestions to your audience data. If you're choosing a new tool, Mailchimp is the easiest starting point, HubSpot is best if you need a CRM, and Omnisend fits ecommerce. Use any generator's output as a starting point, and A/B test the top candidates before sending to your full list.

Prices and features change often, and most of these rankings come from comparison blogs rather than official tests, so confirm the current plans on each vendor's site before buying.

Many modern email marketing platforms now include built-in AI tools designed to help you brainstorm, generate, and optimize subject lines. Since these features are often integrated directly into the email builder, they can be more effective than standalone tools because they "know" your email content, campaign goals, and sometimes even your historical performance data.

Here are some of the top platforms that offer AI-powered subject line suggestions:

1. Platforms with Deeply Integrated AI

These tools are ideal if you want an all-in-one solution where the AI has access to your contact data and campaign history.

• HubSpot: Features a powerful AI subject line generator within its "Campaign Assistant." It is highly regarded for its ability to pull context directly from your campaign inputs, helping to ensure the suggestions align with your specific goals and audience segments.
• Klaviyo: Offers "Subject Line AI" as part of its generative suite. It is particularly strong for e-commerce because it can draft subject lines based on your brand voice and specific campaign briefs, and it can even suggest content that leverages customer behavior (like past purchases or browsing history).
• ActiveCampaign: Uses AI to help with both content and optimization. It offers subject line recommendations and can analyze campaign performance to refine future suggestions. It is well-regarded for users who need complex automation alongside their AI tools.
• Mailchimp: Includes an AI content assistant that can generate subject lines and email copy. It is often cited as a more "simplicity-first" option, making it great for beginners who want to speed up their workflow without complex configurations.
• Brevo: Provides an AI subject line generator and is frequently recommended as a cost-effective, multichannel option. It is straightforward and accessible for small-to-medium businesses.

2. Specialized or Alternative Options

If you are looking for specific workflows or additional features, these platforms also stand out:

• Mailmodo: Focuses on interactive emails and allows you to generate subject lines and preheaders that match your brand. Its AI can adjust the intent, tone, and personalization level of your subject lines.
• Campaigner: Offers "Audience Intelligence" tools that provide AI-generated subject lines and content suggestions based on your own historical data rather than generic datasets.
• GetResponse: Includes a broad suite of AI features, including subject line generation and "Perfect Timing" send-time optimization, which helps ensure your carefully crafted subject lines reach your audience at the best possible moment.

Tips for Using AI Subject Line Generators

While these tools are excellent for overcoming "blank-page syndrome," keep these best practices in mind to get the best results:

• Provide Rich Context: AI is only as good as its input. Don't just provide a topic; specify your target audience (e.g., "new subscribers" vs. "loyal customers"), the goal of the email (e.g., "drive a sale" vs. "educational"), and the desired tone (e.g., "playful," "urgent," or "professional").
• Treat Them as Brainstorming Partners: Use the AI to generate 5–10 variations, then pick your favorite and manually tweak it. AI-generated lines can sometimes feel generic, so adding a human touch often improves performance.
• Always A/B Test: The most important step is testing. Even the best AI-suggested subject line should be A/B tested against a human-written version to see what actually resonates with your specific audience.
• Check for Spam Triggers: While AI tools help you write, always review the final output to ensure you aren't using "spammy" language that might trigger email filters.

Brevo is a good option: its AI can suggest up to three subject lines for email campaigns, and it supports A/B testing them. ²

Other options:

• Klaviyo — suggests subject lines for campaigns and automated flows, with options to refine or regenerate them. ¹
• Mailchimp — offers AI-generated subject lines and real-time suggestions as you write. ¹⁴