eCart can perform real time shipping rate lookup using FedEx, USPS, UPS, DHL and Australia Post.
the shipping rate lookup takes the shipping address that is entered an checkout, the total cart wight and the stores location, sends that info to the selected shipping provider, the shipping provider then returns a quote for shipping that package that can be used for the shipping porice.
the FedEx, USPS, UPS, DHL and Australia Post servers require that you have an account with them to perform the rate quote lookup.