Disable automatic contact creation for Conversations

We are faced with the same issue - trying to use Hubspot to enable our business but finding it too complex to adminsitrate through this one seemingly simple fix. We are losing contacts and struggling to create meaningful distribution lists as the Contacts database is overwhelmed with New Contacts that our meaningless as they are generated by spam or general business communications. I don’t want to tell my electricity company about the amazing new art one of our artists has created. We just want to actively create new customers when they are deemed to be worthwhile to market to and turn off the automation - why is this so hard?