This article describes the Rate Shopping Service codes Tab.
Sometimes when you use ECO (or rate shopping mode), the system chooses the cheapest tariff. But you need to exclude "unsuitable" service code (for example, the "media mail" is only for mailing advertisements, and the "library mail" is only for books) accordingly usually the warehouse needs the cheapest except the "media mail" and the "library mail".
Instead of always selecting the cheapest service customers now You can select which services are included or excluded in rate shopping.
You can find this option at Clients level in a Billing account settings. You can see in the screenshot below Filter Mode which allows choosing an option you prefer to use.
1) for STAMPS service codes MEDIA MAIL and LIBRARY MAIL are excluded by default;
2) for amazon mws envelopes are blocked by default, only the boxes are available for shipping;
3) for other services, there are no default settings, because they do not have special tariffs.