Congress passed the Postal Accountability and Enhancement Act of 2006 (PAEA). Under PAEA, USPS was forced to “pre-fund its future health care benefit payments to retirees for the next 75 years in an astonishing ten-year time span” — meaning that it had to put aside billions of dollars to pay for the health benefits of employees it hasn’t even hired yet, something “that no other government or private corporation is required to do.” As consumer advocate Ralph Nader noted, if PAEA was never enacted, USPS would actually be facing a $1.5 billion surplus today.
It's not their union nor their "Obamacare" that's causing their losses. It's not e-mail or the internet or FedEx either. It's a Law passed by Congress and this wouldn't be the first time we've had to fix bad legislature of the past.