Most contacts are already defined in HubSpot, some may not be.
I have a list of email messages (subject, message, to_email) and a sender which is registered to HubSpot.
I have all the data required, but I cannot get email messages saved into the contacts' activity logs using the /crm/v3/objects/emails/batch/create endpoint.
Can anyone provide working examples of payloads for POSTing to this API? I tried so many approaches, all didn't work.