President Donald Trump has made no secret of his distaste for the New York Times and The Washington Post — but he can’t stop reading them. And while he hasn’t slung much mud in the direction of the Ochs-Sulzberger family, owner of the Times, he has shown no such restraint with Post owner Jeff Bezos.

Bezos,the world’s richest man, is best known for owning online retail giant Amazon. Amazon uses the US Postal Service for the final leg of many of its deliveries in the US. Amazon undertakes all transport from their warehouses to the post offices nearest the delivery destination itself.

Since his inauguration, Trump hasreportedly met four times with the US Postmaster General Megan Brennan with the express purpose of doubling the rates charged to deliver Amazon’s packages. None of these meetings have been listed on Trump’s public calendar.

Brennan has thus far resisted Trump’s requests, and advised the president that Amazon’s rates are determined by contracts that would have to be renegotiated by a regulatory commission. She also advised the president that the Postal Service’s relationship with Amazon is beneficial to her organization, and went so far as to have a visual presentation prepared to illustrate her points.

But regardless of the evidence, Trump is certain that Amazon’s contract with the Postal Service does not charge the company enough. In addition to Brennan’s explanations and presentation, the Post reported that Treasury Secretary Steven Mnuchin, then-National Economic Council Director Gary Cohn and Domestic Policy Council Director Andrew Bremberg were among Amazon’s defenders in the administration. Cohn has since resigned.

“I am right about Amazon costing the United States Post Office massive amounts of money for being their Delivery Boy,”Trump tweeted on April 3. “Amazon should pay these costs (plus) and not have them bourne by the American Taxpayer. Many billions of dollars. P.O. leaders don’t have a clue (or do they?)!”

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Trump has also accused the Post of being a tax shelter for Bezos, as well as “chief lobbyist” for its owner. It’s not clear when the Bezos-Trump feud started or what triggered it, but it dates back to at least 2015. For his part, Bezos has maintained his silence since reporting on this issue began.

To say that it’s unusual for an American president to single out a US company for this kind of criticism would be understating the facts. After one of Trump’s Twitter attacks, Amazon’s stock price temporarily dropped more than 7%. Meanwhile, the company invites states to compete with each other for new Amazon fulfillment centers and other contracts.

Trump argues that Amazon drives smaller, local companies out of business, which may be true. And there’s plenty of evidence that Amazonpromotes a toxic work environment for its warehouse employees,engages in union-busting, and pays workers so little thatmany rely on Food Stamps. But attacking the company’s contracted rates with the Postal Service fails to address any of those issues.