Email help--I don't understand techie talk?

I received over 50 messages from ‘Root User’ in my Outlook Express. I didn’t open them as I realized ‘root user’ wasn’t someone smoking roots, but a technical term I had seen somewhere. I checked the message properties of one of the first emails from ‘ru’ and found the email it had come from. I also noticed my email along with four others to whom the message was sent. When I looked at the properties of message 50+? there were many many email addresses including mine. The msgs from ‘ru’ are a block, no other msgs inbetween (brain dead, can’t think of the word). I sent the emailer a msg asking him to cease and desist. Is there anything else I can do to avoid messages from people like this? Thanks.