Private carriers FedEx and UPS have cut off delivery service for some retailers, sending massive volumes of packages to the Postal Service.
Source: USPS inundated by crush of holiday packages, leading to delivery delays – The Washington Post
Mailed a letter at the Post Office yesterday. I’m in a small town – but the line of cars was backed up out on to the street.
At this time, all mail is delayed – letters to packages. FedEx and UPS have stopped handling shipments from some of their retail partners too, pushing those packages into the USPS, which has to accept all service requests.