Wall Street Journal--FedEx Corp. FDX +1.42% and United Parcel Service Inc. UPS +0.15% increasingly are moving their own packages through the U.S. Postal Service, putting pressure on the quasigovernmental agency and raising questions about whether the USPS is charging enough for the service.

For FedEx alone, the post office delivers an average of 2.2 million packages a day, or about 30% of the express-mail company's total U.S. ground segment. Read more!

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