Alright... just got an email reply... it said:
"You can send letters to the players agents, which has more of a chance of
them receiving it then sending to us. Players are asked to retrieve fan
mail, but we cannot force them. You can post to the address below."
Private Bag 6060 Richmond South, Victoria, Australia, 3121
So, I'll take a punt on this address.
arvidsson clijsters dulko ivanovic
kuznetsova sharapova stosur