Hi there, First you do need to have ADC installed even if you don't want to synchronize the Exch 5.5 with AD. Only this way the two Exchange will see each other. For OWA you must configure properly the IIS in Exch 2000. The main folders that you have to check are exchweb, exchange and public. The IIS root folder you should have it on Anonymous and the exchange should be basic or integrated but not anonymous. OWA in Exch 2000 uses the AD access control. Be careful how is your user configured. This might be another problem. CV.