If you are running the support tool netdiag on it you then it will most likely find some of the associated problems. One way for fixing the problem is that by illustrating to unjoin the computer from the domain and then again rejoin it again to the computer. Tools like netdom can also be used if you are use to it also with their syntax. Also confirm that your domain computers is also making use of the domain controller as there are mainly favored dns server and never an ISP dns server which are been listed. You should also be able to ping the domain controller by IP address and name from your domain clients and the command nslookup must show only the domain controllers as per the dns server and be able to determine fully competent names of domain computer and the domain itself as in mydomain.com which should show correct IP addresses of domain controllers in it.

It’s motivating that you have mentioned "Never use an ISP dns server."

When I first got the sever last month, it was set up with a DNS server as well as appear to work. I’m also leasing the machines for the use of DHCP
to get IP and DNS addresses. However, after I’ve connected a Pix firewall; for the internet connectivity appear to go down the hill fast. I am also able to get onto web sites very rarely. I couldn't get the updates as a work is around; I put our server's IP address in the DNS settings and the ISP's DNS settings which provides with full connectivity. I would also like to fix this, but I’m not aware about how and the guys who had installed it would fix this for a fee. As far as the original issue is concern, I found an old hard disk and installed it with the new system and client on it. It doesn't need to do something about the run for a particular network application so I don't have to reconfigure it for any one person's that make use of it. Since I detached the user from the server what ensue to the old client's e-mail?

Sorry. I overlooked to reveal that, I make use of Outlook 2003 with an Exchange server. That’s why I considered it deleting a user may matter.

I am not that use to with making use of Outlook 2003 and Exchange yet I would think that the emails are still accessible somewhere. If somebody else here is not able to help me out with the problem then you want me to post in an Outlook and/or Exchange newsgroup.

Thanks a lot! I will definitely try the solution out which you have provided me.