If you're viewing the details for an email in HubSpot, the Internal HubSpot ID(s) would be the campaign_id(s) for the email. Since each campaign represents a specific send of an email, it's possible for a single email to have multiple Internal IDs/campaign_ids.
If you're viewing the details for an email in HubSpot, the Internal HubSpot ID(s) would be the campaign_id(s) for the email. Since each campaign represents a specific send of an email, it's possible for a single email to have multiple Internal IDs/campaign_ids.