Jan 13, 2020 11:03 AM
Apologies for the delayed response.
To clarify, is your ultimate goal to send marketing emails via HubSpot's API?
If so, this currently is not possible. You can programmatically create and update marketing emails with the Marketing Email API, but they must be either be sent in the UI or added to workflows as automated emails.
If I have misunderstood your use case, please describe it in greater detail.
Isaac TakushiHubSpot Developer Support