> If you're talking about the requirement to pre-fund their pension fund, my understanding is that UPS and FedEx (and all private corporations) were already required to do so.

It seems that most observers agree that this is not the case, so it is unclear how you came to the exact opposite understanding. E.g. https://www.bloomberg.com/opinion/articles/2018-04-04/congre... mentions

> The law requires the Postal Service, which receives no taxpayer subsidies, to prefund its retirees' health benefits up to the year 2056. This is a $5 billion per year cost; it is a requirement that no other entity, private or public, has to make.

To be clear, the pre-funding obligation doesn't mean USPS must gradually fund the pension obligations for an employee as that employee works for them, as would be common in private enterprise. Instead the USPS is basically required to set aside the entire pension obligation, at the date of hire. No one else has to set aside millions of dollars the same day they hire someone.

USPS is required to serve every one every where. FedEx/UPS punt their shit to the USPS when it comes to rural america.