Hey Pat... I was thinking, do you know if a user that hasn't enabled private messaging in their User CP can still recieve PM's? Meaning, you can send a PM to them but they won't know it's there until they turn that feature on.
I would think you would get an error if you tried to PM someone who hasn't enabled it. Just a thought, maybe one of the admins can answer that.
If it makes you feel any better, I still had PM's in my tracker that I sent to NE folks back in 2006 that were never read! I finally deleted them a couple months ago.