The bottom of every Listbox message should include one of two links, "Unsubscribe Now" or "Modify Your Subscription". Clicking "Unsubscribe Now" will remove you immediately. Clicking "Modify Your Subscription" will take you to the subscriber dashboard.
On the subscriber dashboard, there will be a big red button at the top of the screen that says "Unsubscribe Now". Clicking that will remove you.
If you are on any other lists, you will see a list of them at the bottom of the screen. At the bottom of that list is a link that says "Unsubscribe from all lists". Clicking that will remove you from all the lists shown.
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