Why is a contact still receiving my emails even though they have opted-out?

When a contact selects the "unsubscribe" link in your email, they are directed to the "Manage Subscription" page. This is where they will uncheck all boxes for any list they may be on. They are then automatically moved to the Master Unsubscribe List. If a contact has followed the above procedure but is still receiving your emails, they may be signed up under another email address as well. They will