Immerse ten 12-ounce jars in simmering water until jam is ready. Wash lids and rings in warm soapy water.
Bring a large pot of water to a boil. Add peaches, 3 or 4 at a time; cook for 30 seconds. Immerse in ice water for several minutes to stop the cooking process. Drain. Peel off skins, core and dice peaches into small pieces.
Combine diced peaches, sugar, raspberries, and lemon juice in a large pot. Cook over medium heat, stirring occasionally, until sugar is dissolved, about 5 minutes. Increase heat to medium-high; cook at a rapid boil for 10 minutes. Stir in liquid and powdered pectin; bring back to a boil. Remove from heat and skim foam off the jam with a slotted spoon.
Pack jam into hot jars, filling to within 1/4 inch of the top. Wipe the rims of the jars with a moist paper towel to remove any food residue. Top with lids and screw on rings.
Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars 2 inches apart into the boiling water using a holder. Pour in more boiling water if necessary to bring the water level to at least 1 inch above the tops of the jars. Bring the water to a rolling boil, cover the pot, and process for 10 minutes.
Remove the jars from the stockpot and place onto a cloth-covered or wood surface, several inches apart, until cool, 12 to 24 hours. Press the top of each lid with a finger, ensuring that the seal is tight (lid does not move up or down at all).