Use single-send in an email to merge custom properties

With the transactional email add-on, you can use the single-send API to merge custom properties. Use this endpoint to render the email, add some customizations, and send the email to the intended recipient.

• In your HubSpot account, navigate to Marketing > Email.
• Create a new email.
• In the main email body, insert the desired personalization tokens. To use a custom property that doesn't exist yet, click the source code icon code and add the token in the code of your email.

• Click the Settings tab and use the Email type dropdown menu to select Transactional.

• Click the Recipients tab and select Save for single-send API.

• Click the Review tab, then click Save for single-send API.
• In the dialog box, click Save email for single-send API. Once saved, you'll get an internal email ID to use with the API in the email Performance tab.

• Copy the internal email ID, then click Go to documentation to push values to the personalization tokens in your email.

Please note: you can find the internal email ID at any time in the email details. In your HubSpot account, navigate to Marketing > Email. Click the name of the email, then click More details to see the Internal email ID in the slide-in panel.