Large truck fleets like FedEx are committed to reducing emissions and operating costs. Electric vehicles are seen as a means to do both as well as meeting toughening regulations in the EU and US when battery costs lower in the next few years.
Background
U.S. mail service has decades-long history of trying and giving up on electric delivery vehicles
Some lacked power to take on hilly routes
Others were undercut by government electric vehicle programs that later expired
Ford introducing Transit Connect electric commercial van later this year w/ 80-mile battery range