In a small saucepan over high heat, bring water and sugar to a boil; cook until sugar is dissolved. Set aside. In a food processor or blender, puree plums, raspberried, port wine, and cooled sugar mixture until smooth. Pour into 8- by 8-inch baking dish. Freeze at least 8 hours or until firm. To serve, scoop sorbet into wine or champagne glasses. Garnish with mint sprigs and raspberries.