Outlook 2003 Exchange Server Not Found

I reciently set up and exchange server on DC to run calendar and contact sharing on a small office network. every thing seemed to be working fine until people started having connection problems with outlook.

when you open outlook it stalls for about 30 seconds then it comes up with an error message "Connection to Exchange Server; Exchange server not found" it has 3 options "retry, work offline, or cancel"

much as i try i cant figure it out

any help would be greatly appreciated!