The Importance of Saving Dunning Letters from Debt Collectors Naturally, I have never met a person who enjoys getting a debt collection letter in the mail. This is true for folks who owe the debt, never owed the debt, or are not even sure whether or not they owe the debt. A “dunning” letter is simply a payment demand letter from a debt collector. These letters simply bring about a feeling of anxiety and a concern about credit, lawsuits, or even more severe consequence