The postal deficit is due to Congress requiring the USPS to prefund employee health benefits for the next 75 years.
you left out the most important part..
So they can raid said fund.
you sir, have a clue! USPS is a cash cow.
The whole point of the prefunding fund was to balance the federal budget ~ to close the deficit. Listen to the Senate committee that came up with the idea ~ this wasn't done to fill any postal need, nor even, really, to do anything about employee retirement. No one working at USPS today, or who has ever worked for USPS would benefit from this particular deal.
In effect, this was nothing but USPS being forced to subsidize the US government!