Receiving letters and postcards is allways nice:
The address is:
Group name and name Labelterrein Bieslandse Bos
2641 ZA Pijnacker
Should you want to send a letter yourself, then the nearest mail box is in Pijnacker or Nootdorp.
At the 'Bruna' (book shop) is a postal agency, where you can send mail, but also buy stamps. There are also cash dispensers there.
We have a telephone on site, but it is only to be used in case of emergencies:
+31 15 369 9073