When you Deploy a Normal Campaign, several options allow you to target subscribers in your List. To prevent messages from being sent to specific subscribers, select ADVANCED OPTIONS and then choose a Suppression List.
The campaign will send to all subscribers in the List except those defined in the Suppression List. The suppressed Subscribers will remain subscribed to the List, but they will not receive the email message from the campaign.
At this time, there is no option to report which subscribers were suppressed after a campaign.