A well-known and very effective way to bounce curse back is for the cursee to put some needles or pins (sharp and rust-proof are best) in a saucepan, urinate on them, and boil it up. The cursor then has his (her) own curse on him(her)self, along with a good pricking from the pins or needles. For extra security, you can put it all in a bottle and bury it under your hearth. Don't be tempted to send the bottle to the cursor, or (s)he can make voodoo dolls with with it.

Steve