Send transactional email to another email also as CC

[SPolczman]

Hi all,

I'm trying to send a transactional email from a custom code action in a HubSpot workflow using the /marketing/v3/transactional/single-email/send endpoint. The setup is very straightforward, I'm passing the contact's primary email address as the recipient, and optionally including invoice_email as a CC if it exists and is different. This is why I have to send it from a custom code, because there is not really another option, the send-email node is only for the customers main email address.

The problem is that the email is never sent, not even to the primary recipient. There are no visible errors in the custom code execution.

To test further, I stripped everything down and tried sending to just the primary email (email) with no CC and no custom properties in the custom code, same result. No errors, but also no email is ever actually delivered or tracked in HubSpot.

I’m using a published transactional single-send template (with ID) that works when triggered manually, so I know the template itself is valid.

Is there something about custom code actions that prevents transactional email sending? Do I need to configure additional scopes or permissions for the workflow to actually send the message?

Any help would be hugely appreciated — right now it feels like the API accepts the call but just silently does nothing.

Thanks in advance!

[ASam26 · Accepted solution]

Yes, custom code can send transactional emails, but a few gotchas:

• Your private app needs the transactional email scope. Without it, the call looks fine, but nothing sends.
• Make sure your sending domain is verified for transactional use.
• Test the exact payload in Postman first. If it works there but not in the workflow, it’s a scope/permissions issue.
• For CC, better to just pass multiple recipients in the message.to instead of forcing CC.

Start simple: one recipient, minimal payload. If that works in Postman, copy it into your workflow.