Any contacts that you have sent an email Campayn to that have bounced, unsubscribed or marked your email as spam will not be sent to again.
We advise that you do not delete these contacts from your list so that they are properly marked and avoid the contact from being added again. Even though the contact that has either bounced, unsubscribed or marked your email as spam remains on your list and you do send to that list again, we will not count it as an email send.