"This is another 'lucky' situation when things turn for better. While making my raspberry jam, I totally forgot to add pectin. The result: exactly the same that if I did add some. Easier, simpler, and less risky than adding pectin to it."
Bring raspberries to a boil in a very large pot. Cook for 4 minutes. Add sugar and lemon juice; stir well. Bring back to a boil, stirring constantly. Cook for another 4 minutes.
Remove pot from heat and pour jam into sterilized jars, leaving 1/4-inch of space at the top. Seal and transfer jars into a boiling water bath. Make sure jars are covered with at least 1 inch of water; let sit for 5 minutes. Lift jars and let them cool in a draft-free place without touching, 8 hours to overnight.