What if an imported lead already exists in HubSpot

HubSpot will automatically de-dupe based on email address

If you've integrated IntentData.io with HubSpot to automatically import leads, it will often occur that an existing contact in HubSpot appears as a lead and is imported. What happens?

The import is managed through a form. (more information on setting it up here.) Therefore the behavior will be as with normal HubSpot forms which automatically de-dupe based on the contact email address. In that case property values will be updated for the same contact record.