Post office in IAD?
 

Has anyone spotted a post office in IAD? An APO would be appreciated.

Does the RCC in IAD handle packages, if I pre-print the USPS label from my computer in advance?

there is one in the building across from the Marriott, I believe ... its on property but not in the airport. As far as RCC taking a package, I think they've stopped doing that. I don't know if its still somewhere in the airport, but outside security there used to be a bin for mailing the objects that TSA wouldn't let you carry on that were too small to check on their own.