I came here to see if there was a solution and I can’t believe after 3 years there still isn’t a solution. It seems as if there should be a “Click box” on the hubspot to exclude domains or emails from being logged as a contact. Even deleting contacts won’t solve the problem because as soon as they reply a new contact is created.
Solution:
In the Hubspot extensions add a click box to never create contacts based on domain or specific emails. In Outlook or Chrome add in the same feature.