Courier Preferences is a new feature announced by the company, allowing developers to build great notification infrastructure effortlessly. It provides a clean interface for users to manage their preferences, including options for customization and integration with core products. The feature can be used to implement fine-grained and easy-to-use notification preferences that respect user choices. It offers various benefits such as reducing engineering resources, improving user experience, and increasing visibility of the company's products. Courier Preferences can be used to build a bespoke notification experience or embed pre-built UI components, and it provides a free tier with features like multiple sections and personalized Preference Center links. The feature also includes tools for managing unsubscribe experiences and logging user preference changes.