I have an exchange server at one location and have 3 remote sites. There are DC's at all sites and are setup as Global Catalogs. When I setup an email for new users, OWA works but configuring Outlook I cannot connect the the exchange server. It tells me that the server is not online or not responding. They can ping the exchange server, they can even open shared files on the exchange server. The remote sites are connected with a T1 connection to the main office. What port does Outlook use to connect to an Exchange server. I was thinking it might be with the router not letting a certain packets in due to a port not opened or configured?