Dear Wisdombeing,
I agree 100 percent that we do not want any harm to come to the sender; so Dorje Shugden should be able to keep them from being harmed, while protecting us, if that is what we pray for. We can also do Vajrasattva for them since we obviously have some karma with them, and don't want them to fall into the lower realms.
--------------------------------------------------------------------------------
Quote from Wisdombeing
"I think that most mantras will protect - after all, mantras are the enlightened energy of the Buddhas as sound. i personally think that Dorje Shugden's mantra is most appropriate because he is the Dharma Protector for me (and most people who visit this site). Dorje Shugden's mantra won't bounce the black magic onto the caster - the caster's negative karma from sending black magic will bounce back to him, whether we are protected or not. So in the spirit of bodhicitta, we should not hope that the magic will harm the caster but feel compassion for him/her because they will bear the consequences."