"set u" (userdomain/userdnsdomain)
will only return the *user* domain, that is, the domain the current *user* is logged on to. This is NOT necessarily the same as the domain that the machine is joined to, for example if a trust is involved.
Is this machine specified in FQDN or a simple host name?
Have you tried to resolve its IP address using nslookup (will ignore the hosts file!) or through ping (will use hosts file, if defined), as single host name and as fqdn?
vickzz,
apart from the examples I listed above: do you really think "
www.microsoft.com" is a single host that's actually named "www"?
And let me assure you that it's possible to do a server migration where the new server is accessible with the host name of the old server, even though the new computer name is named completely different.