I have a web app where users place orders for items that we need to ship. Instead of entering the shipping info into usps.com (for instance) manually, is there an app that I can send shipping info to via an API whenever an order is made, and then simply visit the site to see all of the shipping labels that I need to print? I don't really care about what carrier we use. I'd appreciate any help
FedEx has the Ship Manager API, I wouldn't be surprised if UPS has one as well.
Check out this pdf link for more information directly relating to shipping labels. :)
Both FedEx and UPS have facilities to file new mailings with them automatically, I would assume the same for USPS.