Exchange Server 2003 issue

Hi,

I need some help regarding the connection of client PCs to Exchange 2003.Some client PCs are using MS Outlook 2003 and some are using Outlook Express. I tried so many configurations but didn’t come up with anything productive. I have configured smtp protocol settings, address book and so many other things.

Someone please help me about what are the pre-requisites to be taken care of on the Exchange 2003 to allow clients to connect to their mailboxes properly.

Thanks a bunch.