In Magento a user can be subscribed to your newsletter without a customer account, so you might be wondering what will happen with records like that. These "non-customers" will not be included in the initial import.
The Connector does account for this scenario, but it is important to note that by default, the newsletter subscription sync is disabled in the connector setting page.
You can enable the Newsletter Subscriber sync on www.hubspotintegration.com if you need this information on your HubSpot portal. Once it is activated, the connector gets all the newsletter subscribers. So it will only update contacts who have an active subscription to Magneto newsletters. If the contact does not exist on your HubSpot, it will create new contact.