Email Stopped Sending to Imported List

I imported a list of contacts for a mass email (approximately 433 contacts) and received a notification that our email send was stoppd due to an unusually high hard bounce rate. How can I clean up our list to be able to finish sending our email without risking our account being suspended? Each of the contacts that are on the list we tried to send to already receive emails from our company, just from a different platform, so we are authorized to send them emails. How can we adjust our list to be able to send them email communications through HubSpot?