The U.S. Postal Service is so much a part of this country, it's in the Constitution. And yet with so much written communication now delivered via email, text messages and the Internet, the Postal Service is steadily losing business and operating in the red.

Postmaster General Patrick Donahoe has given Congress until May 15 to find a way to keep the Postal Service solvent or he will start closing possibly hundreds of its facilities. The U.S. Senate passed legislation Wednesday aimed at shoring up the Postal Service while delaying proposed cutbacks. Now the issue moves to the House.

The post office delivers more than 500 million pieces of mail every day, six days a week, to 150 million addresses. Still, that's about a 20 percent drop in the volume of mail it handled just five years ago.

Though the Postal Service is supposed to be entirely self-financed, it's had to borrow $13 billion from the Treasury over the past two years to stay afloat. Sen. Susan Collins, R-Maine, a chief co-sponsor of the Senate bill to save the Postal Service, says a failure by Congress to act fast could amount to a death sentence.