*so how is it that I get e mail that is not addressed to me?*
The short answer is that you can't and you don't.
What is happening is that your email address is in the BCC (Blind Carbon Copy) address field - so no-one ever sees it. You can only see addresses in the To and CC fields.
Many legitimate and spam bulk mailers use this legitimate privacy technique, as it hides your address from all the other recipients.