That would be very cool, TM26 but its just not going to work.
This is because its soo hard to get pop ups personalised as a messege, and Admin will havw to type up each messege into a HTML box thing and really, why not send PM's because a pop up comes when they come and then you just click on it! So really, this 'post office' is a waste of space maybe a TG could delete it because it is wasting space. No offence, but this idea is too fiddly and well... oh lets just say its a good idea but its not possible.
Regards,
GotchiGirl
PS. Can a TG add stuff to the site? Cos if they could then you could ask a dedicated TG to put the messeges into HTML boxes. Oh but wait... its hard because if u did it as a pop up everybody would see it... hmmm oh well cya around tamamama26