Sounds like someone I know. Abusive, Nuts, Obsessed, Still single..only it's been 25 years.

I would just set up email to auto-delete emails from him or put in a hidden folder in case some day you're bored and want to read them. If he signs his name at the end of his emails, put that on your filter list. Some emails have it where you can set up to only accept email from your "contact" list. I think Outlook does that. Or make a new email if possible.