Elmer T. Klassen, 81, the U.S. Postmaster General who played a major role in takingthe Post Office Department from under the control of a Cabinet officer and making it into anindependent agency in the executive branch. In 1972 under new federal legislation, Klassen, a one-time messenger for American Can Corp. who rose to the presidency of that $1-billion company, became the first postmaster general named by the Postal Service's Board of Governors. He was the nation's 60th postmaster general and served until 1975 when he retired. During his tenure the Postal Service came under congressional criticism because of organizational problems and higher rates. In Palm Harbor, Fla., on Tuesday of heart failure.