No, you cannot, since we currently do not integrate with Stamps.com. However, you can still ship via USPS using an Endicia or Express 1 account. We recommend opening an Express 1 account since it will give you access to USPS Commercial Plus pricing as well as an Express 1 and Endicia account at the same time.
If you do not have an Endicia or Express 1 account yet, you can open one directly from Skubana. For more details, see Adding Shipping Providers.