I have OWA setup in the DMZ. Exchange 5.5 bridgehead server on trusted, with a further 5 Exchange 5.5 servers at other locations off the bridgehead. The OWA server looks to the bridgehead for the mailboxes etc. However, for domain authentication to take place when logging on to OWA at present, I have to allow all ports open from the DMZ to trusted. This is not acceptable and I need advise as to which ports I need to open to allow domain authenitcation. I have read all the Technet articles, but these do not seem to help.