I am being harrased by my childs grandmother(My daughters fathers mother)....?

How do i block her from emailing me.i have already blocked her from my facebook.i don't want her in my life because her son was very abusive and is using my daugher as a pawn to find a way to attack me.also he still has a warrant from last year for assaulting me.and i know he is living at her house.is there a way i can report this because the police are still looking for him.thank you