Exchange server DNS (setup)

A groupwise backround in a Lotus Notes company. Now we are upgrading to Exchange. I have the calendar running. (Not hard) One test user couldn’t send email out. Thought needed Internet Mail Service. It was that users client but during setting up of that service can’t get past the wizard asking for DNS to be setup on the server. Well have set that up for the server by putting server name in host and our .com in the domain name box. Put the IP address for that server in the search order.And wizard still stops and tells me to add the DNS????

Any suggestions … Did reboot of course..

Thanks