Email bounces are automatically processed by Lead Liaison. After processing your emails, subscribers will be marked appropriately, and you can access all bounce related statistics from the Email Reports > Standard > Statistics Emails section.
Hard bounces will mark a Subscriber as "Bounced" by the application after one bounce, and deal with problems like "email address doesn't exist" or "invalid domain name". Soft bounces take 5 times to remove a subscriber from your list, and deal with more common problems like "relay problem" or "mailbox is full". In case of a soft bounce our system tries to send the messages for 3 days. Attempts decrease over this time period (several delivery attempts during the first hour, then a couple times only during the 3rd day).