Is this client a static IP or is it a DHCP client? From this problem client, can you ping the exchange server by name? How about "nbtstat -A " from the client -- does this return several lines of information or an error?
If the above tests produce errors, then name resolution on the client (DNS Server, etc.) is incorrect or there are firewalls or improper routing between the client and the server.
Also double check the spelling of the exchange server name in the Outlook mail account properties, and/or sometimes you have to use the FQDN of the exchange server, i.e. "exchangesvr.yourdomain.local" instead of "exchangesvr"