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Generate subject lines for marketing emails using HubSpot AI

Last updated: February 7, 2024

Available with any of the following subscriptions, except where noted:

All products and plans

You can generate an effective and engaging subject line for your marketing email using HubSpot AI. This allows you to focus your time on refining and optimizing the content of the email campaign itself.

Please note: Please avoid sharing any sensitive information in your prompts. To improve the product, HubSpot logs and stores your prompts, generated language, and usage metrics when you use AI content assistant. HubSpot shares your prompts with OpenAI in order to enable your use of this tool and OpenAI will store your prompts for content moderation purposes. Your prompts will be attributable to you. By using this tool in beta, you agree to comply with HubSpot’s Beta Terms as well as OpenAI’s Usage Policies, Content Policy, and Sharing & Publication Policy.

Understand AI-generated content best practices

  • Proofread and edit your AI-generated content before publishing it.
  • Edit AI-generated content to maintain your brand's voice and style.
  • Balance the use of AI-generated content with content written by a human.
  • While HubSpot has security measures in place, content assistant may occasionally generate incorrect, biased, offensive, or misleading information. Verify the accuracy of the output's content, especially any statistics or facts.
  • The large language model that powers content assistant tends to produce inconsistent results in non-English languages. HubSpot is working on better supporting these languages in the coming months. For now, use extra care in checking non-English content for accuracy and clarity.

Manage subject line assistant setting for all users

By default, the subject line assistant will be available to all users in your account. You can turn this setting off in your account settings:

  • In your HubSpot account, click the settings settings icon in the top navigation bar.
  • In the left sidebar menu, navigate to AI Assistants.
  • Read through the terms of use for AI assistant. If this setting is already turned on, and you unselect the checkbox, content assistant will automatically be turned off.
  • If content assistant is already turned on, you can click to toggle the switch off. 

Generate subject lines using HubSpot AI

To generate a subject line for your marketing email:

  • In your HubSpot account, navigate to Marketing > Marketing Email.
  • Click the name of a drafted marketing email.
  • Click the Settings tab.
  • Under Subject line, click Generate.
  • After a short delay, three subject lines will be generated for you to choose from:
    • To use one of the generated subject lines, click Insert. If you want to iterate on one of the specific lines, click More like this to generate three new subject lines that are similar in sentiment.
    • If none of the originally generated lines fit the tone or theme or your email, you can click Generate new ideas to generate new subject lines.
    • As you generate potential subject lines, you can click the left arrow and right arrow icons in the bottom right of the dialog box to review the options that've been created so far.


You can also generate subject lines for your marketing emails using the HubSpot mobile app. Learn more about how to design and edit emails in the mobile app.

Please note:

  • After the first time you generate your first set of suggested subject lines, you can only generate new ideas up to five additional times for a single email.
  • The generated subject lines will be in the language you set in your marketing email settings.
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