E-Mail not receiving

Am running sbs2000 server on a network with 10 workstations. Problem can receive e-mail on the server, but not on the workstations. Am using internet mail not exchange server. Tried connected the cable modem to one computer I then can receive mail on that computer. Have checked all settings and they seem all correct. Something is preventing me on the server settings from the workstations receiveing the mail. Error cannot find host. Can connect to the internet and have access to the network. Not sure what setting is stopping me. Any help would be appreciated on what setting to check.

Thanks