I think blocking him is only part of the problem. You need to make him stop sending you messages.

One possibility is to use a program like mailwasher (freeware from www.mailwasher.net). This will sit in your system tray (sorry Mac guys - its a PC thing) and watch your mailboxes. When you receive mail from the accounts it will alert you and show you the message headers. It will determine if it thinks it is spam and has a rule-based setup for determining that (including blacklists, etc).

The interesting part is that it can "bounce" the mail. This returns a message to the sender with the annoying "Mail Delivery Subsystem" that emulates a no-user on system situation.

It might be worth checking out.