I can't find the thread, but we mentioned that AMZ packages had shifted to postal service delivery around xmas 2016. This was just confirmed by my local carrier. She says it's overwhelming and the post office is sending them out on a repeat of their routes to handle the volume. The PO has shifted large packages to a 2nd set of contract carriers, but that in't working well --at least here in rural areas.
That's all I could find out.
Postal service does Sunday delivery of packages here. I'm getting some Amazon Prime packages next day: ordered Sunday afternoon, received Monday via USPS. Amazing.
Here, it has been UPS, + Fedex, + USPS, and now Amazon is hiring its own last-mile delivery drivers. They arrive in their own cars/plain clothes. Part time only, but driver said ~$18/hour.
E-commerce is clogging American cities with real delivery trucks
http://boingboing.net/2017/04/30/e-commerce-is-clogging-america.html
I put in a circular drive to handle the delivery truck traffic at the house.
I never use the front door in the winter. The only reason I shovel snow from the front walk is for the UPS and USPS guys bringing Amazon stuff.