I like it--but just as with a protective order, it's good only to the extent you're willing to follow through with it. If you don't, he will know only that he "got to you" and that you won't do anything about it, and he will have "won," in his mind.
If you're prepared to follow through, each and every time--even if the police don't do anything the first, or even the second time--then it's a good strategy. His continued emailing of you after receipt of that email would seem to fall squarely within the harassment statute.
Hey, it's never too late to go to law school.
