Based on the information available, it seems that Shippo allows you to connect your own UPS, USPS, and FedEx accounts if you have them. However, it is important to note that you can also use Shippo's pre-negotiated rates with these carriers if you do not have your own accounts. This means that you are not required to have accounts with these carriers in order to use Shippo's services. But, if you want to use your own negotiated rates, then you would need to connect your own accounts. For more specific details, please check Shippo's official website or contact their customer support.