You can see what emails have bounced back when you click on MARKETING and then TRACKING. In your list of campaigns, there is a column labeled BOUNCED that will show how many bounced emails have occurred from a specific campaign.
To see what email addresses bounced, hover over TRACKING and click on BOUNCED. This will bring you to a list of instances when an email bounced. You can click on one of the email addresses to bring you to a contact entry to update it if necessary.