If it is your email account, just change the password. If he is making false claims, you could end up being implicated. Protect yourself. I suggest seeing a local attorney for a consult. One solution may just be a letter from the attorney. If he fails to comply, then the attorney is on hand for a followup request to the courts for a restraining order.
We do not have a client/attorney relationship until you make an appointment, we discuss your case face to face, I accept a retainer, and we explictly agree to enter into representation.