"name lookup" occurs whenever a computer (your browser, or in the case of this USPS lookup, your server) attempts to find the IP address associated with the URL being accessed.
For you to connect to www.zen-cart.com from your PC, your computer must first do a nameserver lookup to find out the correct address. And then it directs the request to the proper IP address. Same when your store attempts to contact USPS for a shipping quote.
When your webserver can't perform a lookup, it means your server's internal nameserver service isn't operating properly. That could be caused by many things such as outdated DNS cache, a malfunctioning subsystem on the server, and more. ALL these things are up to your hosting company to resolve, because they're issues with your webserver.
THE ONLY THING YOU CAN DO ABOUT IT is get your hosting company to fix the problem.



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