Clients are unable to connect through exchange using 2003 outlook on the LAN side, but they are able to get to all of the emails through the outlook web access from the LAN and outside.The server is running windows small business server 2003 which includes exchange. Theserver also has ISAserver running on it. The server has two network cards one serving as the LAN and one serving as the WAN which acts in accordance with the ISA serverWe checked the event viewer on the server and did not find any errors under the application and system folders. All of the exchange services were upand running. The clientsare able to send and receive between exchange mailboxes and the outside world.We were able to connect to the exchange server using smtp port 25 using telnet from the outside, but were unable to connect through the LAN. Is there a reason why exchange will accept smtp connectivity from the outside but will fail whentrying to connect through the local area network?

I think ISA is blocking ports you need internally. Have you tried RPC ping? http://support.microsoft.com/kb/831051 It may at least tell you what is being blocked in regards to Outlook clients attaching to the server.

I am sorry I wasn't specific enough. We have rules setup in ISA that accept all smtp and http traffic from the LAN or internal network. The clients are actually able to connect to outlook webaccess through the LAN. Outlook 2003 just will not connect to the exchange server when launched.

My boss found an article that has a fix for the problem. It is a known issue with service pack 2. Here is the link to the article that has the known fix. http://support.microsoft.com/kb/555912