In general terms, an unsubscribe is a great way for your email system to purge itself of uninterested users. There are times, however, when a user will vacate your experience because they've forgotten what you offer, they haven't been appropriately segmented, or they don't appreciate your awesomeness. To manage this scenario we always redirect an unsubscriber to a page based on the list they're leaving (the image shows the 'Unsubscribe Redirect' options - you simply a page from a select menu for each list).
You'll be surprised how many users jump back onto your list after you provide them with a little more information and incentive
A single USR (Unsubscribe Subscription Ratio) graph is available for each list and all aggregated lists so you:re able to measure the success of these 'campaigns'.