harvey, you should see if you can add something to your php code that marks if the message has been read or not. it'd be 1 extra column in your messages table set as a bool value and when people go check their message history they can see if its been viewed or not. just put an sql statement to set it to true AFTER the message has been displayed (like at the bottom of the php file that actually shows the message)...that way you know someone read the message. just something to think about that isn't too hard to do.
The only real drug problem is scoring real good drugs.