Do us postal workers get social security?

"Postal Service employees are covered under either the Civil Service Retirement System
(CSRS), the Dual System, or the Federal Employees Retirement System (FERS).
Coverage is based upon the starting date of employment with the Postal Service.
Employees may also participate in the Thrift Savings Plan, which is a defined
contribution retirement savings and investment plan.

Civil Service Retirement System. Under the Postal Reorganization Act, career
employees are covered by the Civil Service Retirement System, which provides a
basic annuity, at a minimum retirement age of 55, determined by the combination of
years of service and high-three years average salary. The CSRS covers substantially
all employees hired before January 1, 1984.

[Dual Civil Service Retirement System (Dual System)/Social Security System.
Employees with prior U.S. government service who were hired between January 1,
1984 and January 1, 1987 are covered by the Dual Civil Service Retirement
System/Social Security System.

Federal Employees' Retirement System. Effective January 1, 1987, career employees
hired since December 31, 1983, except for those covered by the Dual System, are
covered by the Federal Employees' Retirement System. This system provides a basic
annuity, at a minimum retirement age of 62, determined by the combination of years of
service and high-three years average salary. An additional annuity in the form of Social
Security benefits is also received, as well as benefits from the Thrift Savings Plan. Only
under the FERS plan does the Postal Service contribute to the Thrift Savings Plan. A
minimum contribution of 1 percent per year of basic pay is made. Employee voluntary
contributions up to 3 percent of basic pay are matched, as well as 50 percent of
contributions between 3 percent and 5 percent of basic pay, for a possible match
of up to 5 percent."

Source: http://www.usps.com/strategicdirection/_pdf/AppendixD.pdf

Note that casual employees before 1984 were also covered by Social Security.