This is a major roadblock for us and we need HubSpot to pull through on this idea ASAP to make the platform work for us. We already built a custom object in Salesforce to track multiple contact emails per contact and need to sync these emails with the HubSpot emails field. For some reason, the updated primary email in HubSpot cannot be synced back to Salesforce in our current implementation as that led to other problems, so we have to push the updates into HubSpot from Salesforce and vice versa.