The Post Office is closing its doors for good for the first time in 20 years.

The Postal Service said Thursday that it has about $5.6 billion in cash reserves that could be used to service the retirement of the nation’s largest mail carrier, the United States Postal Service.

The service’s biggest financial risk was the closure of the Post Office’s three main hubs in New York, Chicago and Philadelphia.

The Post Offices of New York and Chicago, in suburban areas of the city, and Philadelphia’s Post Office, are the only two major commercial post offices in the country.

The other two are located in Detroit and Pittsburgh.

A spokesman for the Postal Service, Chris Lipske, said the agency will begin using cash reserves to meet its obligations to its customers starting in 2019, and then use that money to pay off its debt.

The Postal Service had $5 billion in its account in 2019.

The agency said it was considering refinancing the bonds it has issued in recent years to try to keep the business afloat.

The shutdown is expected to cost about $1.8 billion a year, and there is uncertainty about how long it will last.

The company is on track to have about $7 billion in assets in 2019 and $10 billion in 2019 cash.