Re: usps shipping stampscom
Let me share my thoughts about this 3rd party app integration.
I've checked our QuickBooks Apps Store and didn't find the app you mentioned. Although you can visit the page and look for an alternative app that will work for you.
Another option for you is to have the Stamps.com app developer contact our Intuit Developer page so it can be integrated.
I'll be here to assist whenever needed. Don't hesitate to leave a comment below and I'll get back to you.