Lately all of my Amazon orders have been delivered by their own courier service. I find this maddening, because they don't offer detailed tracking, hold requests, redirection, or delivery window selection like UPS and FedEx offer their customers. In fact, last week I had to cancel an Amazon order because it shipped earlier than they estimated, which meant I wouldn't be home to receive it. If it had been a FedEx or UPS package, this would not have been a problem.
Unfortunately, Amazon does not allow you ti opt-out of using their service, which means that I am ordering from Amazon less often than I would otherwise, just to avoid their substandard delivery.