Go to Tools, Message Rules, Mail. Select 'New' to create a new message rule and click the option titled 'Where message body contains words...' Type in (separately) each word or combinations of words you want to stop and then choose 'Do not Download From Server' etc. It seems to work so far but I do admit I'm confused by how the rule says 'Apply following rule after the message arrives and then gives you the option of 'Delete from Server'. Seems to work though!
Nick