DNS problem

I have one AD DNS primary server, one win2k member as a secondary DNS server.

1st question: I get an error per hour from AD DNS primary server’s event view states “Windows cannot determine the user or computer name. Returen value (5)” (event ID: 1000). I am sure the DNS configuration is correct on server. what’s wrong? or it’s telling me the problem on client side.

2nd question: DNS server configuration on my win2k workstation, there’s no problem to access Internet no matter put AD primary, secondary or ISP DNS IPs as Preferable DNS, but my outlook’s unable to send/receive email if primary or secondary DNS IP is put on the prefereable DNS. (outlook pop up for SMTP address)