The U.S. Postal Service said its annual loss widened to $8.5 billion in the year ended Sept. 30, exceeding its forecast, as the volume of mail declined. Revenue fell 1.5 percent to $67.1 billion for the year and mail volume dropped 3.5 percent, according to a presentation to the service’s board today at a meeting in Washington, D.C. The loss in the previous fiscal year was $3.8 billion, the service said. The Postal Service, which had forecast a $7 billion loss, said almost two thirds of the deficit, or $5.5 billion, covered health-benefit costs for future retirees.