About a half-billion net, I believe.
While it simply isn't relevant - since neither FedEx nor UPS have any legal obligation to provide service under Federal law, unlike the USPS - what are the numbers you are claiming for FedEx and UPS?
They all get taxpayer support for infrastructure - roads, airports, etc.
None get taxpayer money for routine services.
The postal service is reimbursed by the taxpayers for some, but not all mandates - free mailing of material for the blind, overseas ballots, etc, but not, as far as I know, franked mail from politicians.
So if the person receiving the mail is a blind taxpayer, your point is well taken. Otherwise, it is not.