Tsk, tsk, tsk, Mr DeHaven. I must find you guilty of omitting one single little 6 letter word from your story that would totally change the context of what you are "reporting".
The payment that the USPS WILL default on has nothing to do with any sort of retiree benefits. Those benefits are, and have been fully funded for decades. What this payment is for is for the Health benefits of FUTURE retirees. This fund is being funded to sit and eventually be used to pay for benefits 75 years in to the future.
Here, you can see how much a difference one word can make.
"payment into a federal fund for postal retiree health benefits", your statement.
"payment into a federal fund for FUTURE postal retiree health benefits", my statement.