Ok, I am tired of getting the message that people's PMs are full.
Remember to delete not only your 'received' list but also your 'sent' and 'tracking' lists. Otherwise you will be wondering why no one can send you a PM.
I don't have to wonder. It is a very rare occasion that I ever get a PM. I know my area is cleaned out since I do delete old ones and I have never opted to save any copies or whatever.